49 results on '"Zhi-Jun Qiu"'
Search Results
2. An Ultrafast WSe2 Photodiode Based on a Lateral p-i-n Homojunction
- Author
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Chun Zhao, Changjiang Nie, Youwei Zhang, Wei Hong, Shun Wang, Zhi-Jun Qiu, and Ma Kankan
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Materials science ,business.industry ,General Engineering ,General Physics and Astronomy ,Photodetector ,02 engineering and technology ,Photodetection ,Specific detectivity ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Photodiode ,law.invention ,Responsivity ,law ,Optoelectronics ,General Materials Science ,Electrical measurements ,Homojunction ,0210 nano-technology ,business ,Diode - Abstract
High-quality homogeneous junctions are of great significance for developing transition metal dichalcogenides (TMDs) based electronic and optoelectronic devices. Here, we demonstrate a lateral p-type/intrinsic/n-type (p-i-n) homojunction based multilayer WSe2 diode. The photodiode is formed through selective doping, more specifically by utilizing self-aligning surface plasma treatment at the contact regions, while keeping the WSe2 channel intrinsic. Electrical measurements of such a diode reveal an ideal rectifying behavior with a current on/off ratio as high as 1.2 × 106 and an ideality factor of 1.14. While operating in the photovoltaic mode, the diode presents an excellent photodetecting performance under 450 nm light illumination, including an open-circuit voltage of 340 mV, a responsivity of 0.1 A W-1, and a specific detectivity of 2.2 × 1013 Jones. Furthermore, benefiting from the lateral p-i-n configuration, the slow photoresponse dynamics including the photocarrier diffusion in undepleted regions and photocarrier trapping/detrapping due to dopants or doping process induced defect states are significantly suppressed. Consequently, a record-breaking response time of 264 ns and a 3 dB bandwidth of 1.9 MHz are realized, compared with the previously reported TMDs based photodetectors. The above-mentioned desirable properties, together with CMOS compatible processes, make this WSe2p-i-n junction diode promising for future applications in self-powered high-frequency weak signal photodetection.
- Published
- 2021
3. Remarkable quality improvement of as-grown monolayer MoS2 by sulfur vapor pretreatment of SiO2/Si substrates
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Jing Chen, Fei Chen, Chunxiao Cong, Garel Ekoya, Ran Liu, Junjie Sun, Wenzhong Bao, Rong-Jun Zhang, Zhi-Jun Qiu, Laigui Hu, Haomin Wang, Jinkun Han, Yabing Shan, and Peng Yang
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Materials science ,business.industry ,chemistry.chemical_element ,02 engineering and technology ,Chemical vapor deposition ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Sulfur ,Optical quality ,0104 chemical sciences ,Characterization (materials science) ,Semiconductor ,Chemical engineering ,chemistry ,Fundamental physics ,Monolayer ,General Materials Science ,Direct and indirect band gaps ,0210 nano-technology ,business - Abstract
Monolayer MoS2 is a direct bandgap semiconductor which is believed to be one of the most promising candidates for optoelectronic devices. Chemical vapor deposition (CVD) is the most popular method to synthesize monolayer MoS2 with a large area. However, many defects are always found in monolayer MoS2 grown by CVD, such as sulfur vacancies, which severely degrade the performance of devices. This work demonstrates a concise and effective method for direct growth of high quality monolayer MoS2 by using SiO2/Si substrates pretreated with sulfur vapor. The MoS2 monolayer obtained using this method shows about 20 times PL intensity enhancement and a much narrower PL peak width than that grown on untreated substrates. Detailed characterization studies reveal that MoS2 grown on sulfur vapor pretreated SiO2/Si substrates has a much lower density of sulfur vacancies. The synthesis of monolayer MoS2 with high optical quality and low defect concentration is critical for both fundamental physics studies and potential practical device applications in the atomically thin limit.
- Published
- 2020
4. High-Performance WSe2 Photodetector Based on a Laser-Induced p–n Junction
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Qiyuan Wang, Wenzhong Bao, Laigui Hu, Shan Yabing, Jing Chen, Yaochen Sheng, Fuyou Liao, Ran Liu, Chunxiao Cong, Gaoqi Cao, Zaheer Muhammad, Zhi-Jun Qiu, and Peng Yang
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Photocurrent ,Materials science ,Laser scanning ,Ambipolar diffusion ,business.industry ,Doping ,Photodetector ,Heterojunction ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,0104 chemical sciences ,law.invention ,law ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business ,p–n junction - Abstract
Two-dimensional heterojunctions exhibit many unique features in nanoelectronic and optoelectronic devices. However, heterojunction engineering requires a complicated alignment process and some defects are inevitably introduced during material preparation. In this work, a laser scanning technique is used to construct a lateral WSe2 p-n junction. The laser-scanned region shows p-type behavior, and the adjacent region is electrically n-doped with a proper gate voltage. The laser-oxidized product WOx is found to be responsible for this p-type doping. After laser scanning, WSe2 displays a change from ambipolar to unipolar p-type property. A significant photocurrent emerges at the p-n junction. Therefore, a self-powered WSe2 photodetector can be fabricated based on this junction, which presents a large photoswitching ratio of 106, a high photoresponsivity of 800 mA W-1, and a short photoresponse time with long-term stability and reproducibility. Therefore, this selective laser-doping method is prospective in future electronic applications.
- Published
- 2019
5. Humidity effect on photoelectrical properties of photosensitive field effect transistors
- Author
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Yiqiang Zhan, Lirong Zheng, Kunlong Yang, Fernando Seoane, Zhi-Jun Qiu, Akrajas Ali Umar, and Sijian Yuan
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Photocurrent ,Materials science ,business.industry ,Humidity ,02 engineering and technology ,General Chemistry ,Photoelectric effect ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Biomaterials ,Organic semiconductor ,Decay time ,Materials Chemistry ,Optoelectronics ,Field-effect transistor ,Relative humidity ,Electrical and Electronic Engineering ,0210 nano-technology ,business ,Polarization (electrochemistry) - Abstract
Environmental influences are critical for the reliability of photoelectric devices, especially those using organic semiconductors. Among all the influence factors, the effect of relative humidity on the material's photoelectrical properties receives less attentions. To date, reported humidity effects are mostly related to the electrical properties. Their impact to the photoelectrical characteristics has rarely been investigated. In this work, we firstly report a detailed study on the dependency of material's photoelectrical properties on the relative humidity in photosensitive field effect transistors. It was found that both the amplitude and the decay time of the photocurrent indicated a profound dependency on the humidity. To further clarify the mechanism, experiments were carefully designed along with a simulation to recognize and to provide a detailed understanding on any possible influence factors in these processes. The results indicate a prominent co-existence of carrier-trapping and dielectric-polarization phenomena in the photoelectric device under the influences of humidity. Since the water molecules in the atmosphere are predominant, the observed variation in the photoelectrical properties can be explained.
- Published
- 2019
6. Influence of seeding promoters on the properties of CVD grown monolayer molybdenum disulfide
- Author
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Ai-Guo Yang, Peng Yang, Ran Liu, Youwei Zhang, Laigui Hu, Chunxiao Cong, Xin-Ping Qu, Zhi-Jun Qiu, Rong-Jun Zhang, Jing Chen, Haomin Wang, and Lingxiu Chen
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Materials science ,business.industry ,Nucleation ,02 engineering and technology ,Chemical vapor deposition ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,chemistry.chemical_compound ,Semiconductor ,Transition metal ,chemistry ,Chemical engineering ,Monolayer ,Molecule ,General Materials Science ,Seeding ,Electrical and Electronic Engineering ,0210 nano-technology ,business ,Molybdenum disulfide - Abstract
Chemical vapor deposition (CVD) is the most efficient method to grow large-area two dimensional (2D) transition metal dichiacogenides (TMDCs) in high quality. Monolayer molybdenum disulfide (MoS2) and seed-assistant are the mostly selected 2D TMDC and growth strategy for such CVD processes, respectively. Though the advantages of seed catalysts in facilitating the nucleation, achieving higher yield and better repeatability, as well as their effects on the morphologies of as-grown MoS2 have been studied, the influence of seeding promoters on both optical and electrical properties of as-grown monolayer MoS2 is not known comprehensively, which is indeed critical for understanding fundamental physics and developing practical application of such emerging 2D semiconductors. In this report, we systematically investigated the effect of different seeding promoters on the properties of CVD-grown monolayer MoS2. It is found that different seed molecules lead to different impacts on the optical and electrical properties of as-grown monolayer MoS2. Among three different seed catalysts (perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt (PTAS), copper phthalocyanine (CuPc), and crystal violet (CV)), PTAS performs better in obtaining large area monolayer MoS2 with good optical quality and high electrical mobility than the other two. Our work gives a guide for modifying the properties of as-grown monolayer MoS2 and other 2D transition metal dichalcogenides in seeding promoters-assisted synthesis process.
- Published
- 2019
7. Organic semiconductor/water interfaces for photoelectrical viscosity sensing
- Author
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Rui Feng, Chunxiao Cong, Ran Liu, Zhi-Jun Qiu, Hanqiu Yi, Su Zichang, Laigui Hu, Chen Cheng, Yajie Qin, and Guoping Chen
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Work (thermodynamics) ,Materials science ,business.industry ,Photoconductivity ,Wearable computer ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Organic semiconductor ,lcsh:Chemistry ,Semiconductor ,lcsh:Industrial electrochemistry ,lcsh:QD1-999 ,Viscosity (programming) ,Electrochemistry ,Optoelectronics ,Lower cost ,0210 nano-technology ,business ,Wearable technology ,lcsh:TP250-261 - Abstract
Most viscosity sensors, which are important in the health, automotive and food production industries, are currently based on mechanical or optical approaches. They are not compatible with emerging flexible and wearable electronics consisting of various lightweight integrated sensors with more compact architecture and lower cost. Here we demonstrate an organic device for sensing the viscosity of nonelectrolyte aqueous solutions which can work at low viscosities (0.9–10 mPa·s). The photoconductivity of devices involving semiconductor/water interfaces was found to obey Walden's rule, suggesting that viscosity could be measured by electrical means. This may be a promising approach for the design of viscosity sensors for portable and wearable applications. Keywords: Viscosity sensors, Organic photosensors, Glucose aqueous solution, Photoelectrochemical cells, Walden's rule
- Published
- 2018
8. Direct laser writing of vertical junctions in graphene oxide films for broad spectral position-sensitive detectors
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Youwei Zhang, Ran Liu, Laigui Hu, Rui Feng, Chunxiao Cong, Zhi-Jun Qiu, Muhammad Zaheer, Yajie Qin, and Qingmiao Nie
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Materials science ,laser scribing ,QC1-999 ,Oxide ,Photodetector ,02 engineering and technology ,010402 general chemistry ,reduced graphene oxide ,01 natural sciences ,law.invention ,chemistry.chemical_compound ,Position (vector) ,law ,Electrical and Electronic Engineering ,business.industry ,Graphene ,Physics ,graphene ,Detector ,021001 nanoscience & nanotechnology ,Laser ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,chemistry ,photodetectors ,Optoelectronics ,0210 nano-technology ,business ,Laser scribing ,position-sensitive detectors ,Biotechnology - Abstract
Heterostructures with built-in electric fields are crucial for charge separation and lateral photovoltaic effect in current position-sensitive detectors (PSDs), which have to be produced by combining semiconductors with metal or other semiconductors to form various vertical junctions (e.g. Schottky junctions) via complicated and high-cost manufacture processes. In the present work, it was found that vertical junctions can be directly written and patterned inside graphene oxide (GO) films with gradient C/O ratios by laser scribing due to the optical filter effect of the films and the formation of reduced GO (rGO) layers. Such junctions were verified to show the capability for high-precision position sensing on the micrometer scale, owing to the lateral photovoltaic effect. These self-powered laser-scribed PSDs can exhibit a small nonlinearity of
- Published
- 2018
9. Intrinsic excitonic emission and valley Zeeman splitting in epitaxial MS2 (M = Mo and W) monolayers on hexagonal boron nitride
- Author
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Zhi-Jun Qiu, Haomin Wang, Jingzhi Shang, Chunxiao Cong, Bingchen Cao, Ting Yu, Pengfei Tian, Chenji Zou, Laigui Hu, Lishu Wu, Ran Liu, and School of Physical and Mathematical Sciences
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Yield (engineering) ,Materials science ,02 engineering and technology ,Chemical vapor deposition ,Epitaxy ,01 natural sciences ,symbols.namesake ,Transition metal ,Physics [Science] ,Transition Metal Dichalcogenides ,0103 physical sciences ,Monolayer ,General Materials Science ,Electrical and Electronic Engineering ,010306 general physics ,Zeeman effect ,business.industry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Semiconductor ,symbols ,Intrinsic Excitonic Emission ,Optoelectronics ,Light emission ,0210 nano-technology ,business - Abstract
Two-dimensional (2D) semiconductors, represented by 2D transition metal dichalcogenides (TMDs), exhibit rich valley physics due to strong spin-orbit/spin-valley coupling. The most common way to probe such 2D systems is to utilize optical methods, which can monitor light emissions from various excitonic states and further help in understanding the physics behind such phenomena. Therefore, 2D TMDs with good optical quality are in great demand. Here, we report a method to directly grow epitaxial WS2 and MoS2 monolayers on hexagonal boron nitride (hBN) flakes with a high yield and high optical quality; these monolayers show better intrinsic light emission features than exfoliated monolayers from natural crystals. For the first time, the valley Zeeman splitting of WS2 and MoS2 monolayers on hBN has been visualized and systematically investigated. This study paves a new way to produce high optical quality WS2 and MoS2 monolayers and to exploit their intrinsic properties in a multitude of applications. MOE (Min. of Education, S’pore)
- Published
- 2018
10. Gbps Long-Distance Real-Time Visible Light Communications Using a High-Bandwidth GaN-Based Micro-LED
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Pengfei Tian, Xiaolin Zhou, Xiaoyan Liu, Yuxin Huang, Zhi-Jun Qiu, Chunxiao Cong, Lirong Zheng, Zixian Wei, Zhilai Fang, Ran Liu, Suyu Yi, and Laigui Hu
- Subjects
lcsh:Applied optics. Photonics ,visible light communication ,real-time ,Visible light communication ,Gallium nitride ,02 engineering and technology ,micro-LED ,01 natural sciences ,GaN ,law.invention ,010309 optics ,chemistry.chemical_compound ,law ,0103 physical sciences ,lcsh:QC350-467 ,Light beam ,Forward error correction ,Electrical and Electronic Engineering ,Physics ,NRZ-OOK ,business.industry ,Bandwidth (signal processing) ,lcsh:TA1501-1820 ,Keying ,021001 nanoscience & nanotechnology ,Atomic and Molecular Physics, and Optics ,high-speed ,chemistry ,Bit error rate ,Optoelectronics ,0210 nano-technology ,business ,lcsh:Optics. Light ,Light-emitting diode - Abstract
In this investigation, we experimentally demonstrated a high-speed Gbps long-distance real-time visible light communication system based on non-return-to-zero on-off keying modulation by using a high-bandwidth Gallium nitride-based micro-LED with a modulation bandwidth of ∼230 MHz and a size of 40 μ m $ \times $ 40 μ m. The maximum real-time data rate obtained is up to 1.3 Gbps at a 3 m free-space transmission distance with a bit-error rate (BER) of 3.4 $ \times $ 10 –3 and 1 Gbps at a 10 m distance with a BER of 3.2 $ \times $ 10–3, both of which are underneath the forward error correction threshold of 3.8 $ \times $ 10–3 required for free-error operation. In addition, when the transmission distance is increased to 16 m in free space through reflecting the emission light beam by blue reflectors mounted on the wall, a data rate of 0.87 Gbps with a BER of 3.5 $ \times $ 10–3 is achieved successfully.
- Published
- 2017
11. Microwave Annealing as a Low Thermal Budget Technique for ZnO Thin-Film Transistors Fabricated Using Atomic Layer Deposition
- Author
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Feng Sun, Lei Yue, Shi-Li Zhang, Chaochao Fu, Zhi-Jun Qiu, and Dongping Wu
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010302 applied physics ,Materials science ,Annealing (metallurgy) ,business.industry ,Transistor ,Gate dielectric ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Temperature measurement ,Electronic, Optical and Magnetic Materials ,law.invention ,Atomic layer deposition ,law ,Thin-film transistor ,Logic gate ,0103 physical sciences ,Thermal ,Electronic engineering ,Optoelectronics ,Electrical and Electronic Engineering ,0210 nano-technology ,business - Abstract
Microwave annealing (MWA) and furnace annealing are compared for their low thermal budget capability to improve the characteristics of ZnO-based thin-film transistors (TFTs). Both the ZnO channel and the Al2O3 gate dielectric are fabricated using atomic layer deposition. Using Si-wafer-susceptor assisted MWA with a substantial reduction of both annealing temperature and duration, significant improvements of the characteristics of the ZnO TFTs can be attained. A multi-step MWA process is found to further improve the characteristics of the TFTs. For the same microwave power and total duration, the field-effect mobility of the multi-step MWA TFT is 42% greater than that of the one-step MWA TFT with a similar sub-threshold swing. The multi-step MWA process can serve the purpose at temperatures as low as 220 °C.
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- 2017
12. Precise Layer Control of MoTe2 by Ozone Treatment
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Jing Chen, Youwei Zhang, Ran Liu, Laigui Hu, Qiyuan Wang, Chunxiao Cong, and Zhi-Jun Qiu
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Ozone ,Materials science ,General Chemical Engineering ,Device Properties ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Atomic units ,lcsh:Chemistry ,chemistry.chemical_compound ,Transition metal ,General Materials Science ,self-limiting ,business.industry ,Ambipolar diffusion ,Doping ,MoTe2 ,021001 nanoscience & nanotechnology ,Layer thickness ,0104 chemical sciences ,ozone ,chemistry ,lcsh:QD1-999 ,Optoelectronics ,0210 nano-technology ,business ,Layer (electronics) ,layer thinning - Abstract
Transition metal dichalcogenides (TMDCs) demonstrate great potential in numerous applications. However, these applications require a precise control of layer thickness at the atomic scale. In this work, we present an in-situ study of the self-limiting oxidation process in MoTe2 by ozone (O3) treatment. A precise layer-by-layer control of MoTe2 flakes can be achieved via multiple cycles of oxidation and wet etching. The thinned MoTe2 flakes exhibit comparable optical properties and film quality to the pristine exfoliated ones. Besides, an additional p-type doping is observed after O3 oxidation. Such a p-doping effect converts the device properties of MoTe2 from electron-dominated to hole-dominated ambipolar characteristics.
- Published
- 2019
13. Fabrication of Uniform Gold Nanopatterns on Graphene by Using Nanosphere Lithography
- Author
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Laigui Hu, Zhi-Jun Qiu, Shan Yabing, Naiyun Tang, Chunxiao Cong, Gaoqi Cao, Pengfei Tian, and QianQian Wang
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Materials science ,Fabrication ,business.industry ,Graphene ,Doping ,Biomedical Engineering ,Bioengineering ,General Chemistry ,Substrate (electronics) ,Condensed Matter Physics ,Nanomaterials ,law.invention ,symbols.namesake ,law ,symbols ,Optoelectronics ,Nanosphere lithography ,General Materials Science ,Surface plasmon resonance ,Raman spectroscopy ,business - Abstract
In this study, we have realized controllable fabrication of gold nanopatterns on pristine monolayer graphene by using nanosphere lithography, in which polystyrene (PS) spheres are used as templates. With this method, periodically ordered triangular Au nanopatterns are uniformly formed on graphene surface. Micro-Raman spectroscopy shows that these sacrificial PS templates have no obvious effect on graphene surface structure while the subsequently formed Au nanopatterns are found to enhance Raman intensity of G and 2D bands by surface plasmon resonance. The compressive stress introduced in the metal deposition process leads to an obvious blue shift of 2D band. Besides, the metal-induced doping effect reduces the intensity ratio between 2D and G bands. This uniform arrangement of metal nanostructure is expected to grow other nanomaterials or used as Raman enhancement substrate in biomedicine, catalyzer and optics areas.
- Published
- 2018
14. Wafer‐Scale Diisopropylammonium Bromide Films for Low‐Power Lateral Organic Ferroelectric Capacitors
- Author
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Husnain Jawad, Ran Liu, Yichen Cai, Laigui Hu, Xiaojie Zhou, Bobo Tian, Mingsheng Xu, Wei Jin, Jiao Wang, Chunxiao Cong, Qingmiao Nie, Zhi-Jun Qiu, Bo Yan, and Mengge Yan
- Subjects
Materials science ,Scale (ratio) ,business.industry ,Ferroelectricity ,Electronic, Optical and Magnetic Materials ,Power (physics) ,law.invention ,Capacitor ,chemistry.chemical_compound ,chemistry ,law ,Bromide ,Optoelectronics ,Wafer ,business - Published
- 2020
15. Trion-induced current anomaly in organic polymer
- Author
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Hui Li, Zhi-Jun Qiu, Youwei Zhang, and Shi-Li Zhang
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Materials science ,02 engineering and technology ,Carbon nanotube ,010402 general chemistry ,Polaron ,01 natural sciences ,Dissociation (chemistry) ,law.invention ,Biomaterials ,law ,Electric field ,Metastability ,Materials Chemistry ,Electrical and Electronic Engineering ,Condensed matter physics ,business.industry ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Semiconductor ,Thin-film transistor ,Trion ,0210 nano-technology ,business - Abstract
In this report, an anomalous time-evolution of electrical current in organic thin-film transistors, OTFTs, is revealed by employing a specially tailored semiconductor composite channel. The composite is designed by controlling the density of carbon nanotubes dispersed in a host semiconducting polymer below electrical percolation. The current anomaly, which, to the best of our knowledge, has never been observed before, is directly correlated to strong many-body interactions instantaneously occurring in the system under investigation. In essence, two on-chain positively charged polarons are fused with an electrochemically generated negative hydroxyl ion, OH−, in the H2O/O2 redox reaction to form a trion. The trion, which is characteristic of the polymer, is intrinsically metastable and can dissociate to mobile polarons under the influence of electric field, temperature and/or light illumination. The rate of trion formation is almost three orders of magnitude higher than that of trion dissociation. The fast formation and slow dissociation of the trions is the cause responsible for the observed current anomaly. The metastable trion is, hence, of fundamental importance in the operation of OTFTs. Understanding the fundamentals pertaining to the anomalous phenomenon not only is crucial for design of more efficient devices but also can guide development of future, emerging applications of OTFTs.
- Published
- 2016
16. Multilayer Si shadow mask processing of wafer-scale MoS2 devices
- Author
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Yong Pu, Zihan Xu, Fuyou Liao, Jing Chen, Qijuan Wu, Hongwei Tang, Haima Zhang, Xiaojiao Guo, Zhi-Jun Qiu, Zhengzong Sun, Hu Xu, Wenzhong Bao, Wei Niu, and Hanqi Liu
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Shadow mask ,Fabrication ,Materials science ,business.industry ,Mechanical Engineering ,Transistor ,General Chemistry ,Semiconductor device ,Condensed Matter Physics ,law.invention ,Mechanics of Materials ,law ,Etching (microfabrication) ,Optoelectronics ,General Materials Science ,Field-effect transistor ,Wafer ,business ,Surface finishing - Published
- 2020
17. Photovoltage Reversal in Organic Optoelectronic Devices with Insulator-Semiconductor Interfaces
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Laigui Hu, Chunxiao Cong, Rui Feng, Guoping Chen, Zhi-Jun Qiu, Ran Liu, Wei Jin, Muhammad Zaheer, and Qingmiao Nie
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Materials science ,Insulator (electricity) ,02 engineering and technology ,organic optoelectronic devices ,010402 general chemistry ,lcsh:Technology ,01 natural sciences ,Article ,Electric field ,General Materials Science ,Photoelectric conversion ,lcsh:Microscopy ,organic photodiodes ,insulator layer ,lcsh:QC120-168.85 ,Photocurrent ,lcsh:QH201-278.5 ,lcsh:T ,business.industry ,organic semiconductor ,021001 nanoscience & nanotechnology ,Space charge ,0104 chemical sciences ,Organic semiconductor ,Semiconductor ,lcsh:TA1-2040 ,Optoelectronics ,Equivalent circuit ,lcsh:Descriptive and experimental mechanics ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,space-charge ,lcsh:Engineering (General). Civil engineering (General) ,0210 nano-technology ,business ,lcsh:TK1-9971 - Abstract
Photoinduced space-charges in organic optoelectronic devices, which are usually caused by poor mobility and charge injection imbalance, always limit the device performance. Here we demonstrate that photoinduced space-charge layers, accumulated at organic semiconductor-insulator interfaces, can also play a role for photocurrent generation. Photocurrent transients from organic devices, with insulator-semiconductor interfaces, were systematically studied by using the double-layer model with an equivalent circuit. Results indicated that the electric fields in photoinduced space-charge layers can be utilized for charge generation and can even induce a photovoltage reversal. Such an operational process of light harvesting would be promising for photoelectric conversion in organic devices.
- Published
- 2018
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18. Laser-based white-light source for high-speed underwater wireless optical communication and high-efficiency underwater solid-state lighting
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Xiaoyan Liu, Zhi-Jun Qiu, Xiaolin Zhou, Suyu Yi, Lirong Zheng, Chunxiao Cong, Laigui Hu, Pengfei Tian, Shuailong Zhang, Ran Liu, and Zhilai Fang
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Physics ,business.industry ,Visible light communication ,02 engineering and technology ,Color temperature ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,010309 optics ,Color rendering index ,Optics ,Transmission (telecommunications) ,Wavelength-division multiplexing ,0103 physical sciences ,RGB color model ,Underwater ,0210 nano-technology ,business ,Data transmission - Abstract
White light generated by mixing the red, green, and blue laser diodes (RGB LDs) for simultaneous high-speed underwater wireless optical communication (UWOC) and high-efficiency underwater solid-state lighting (SSL) was proposed and demonstrated experimentally for the first time. The allowable maximum real-time data transmission rates of 3.2 Gbps, 3.4 Gbps, and 3.1 Gbps for RGB LDs with corresponding BERs of 3.6 × 10−3, 3.5 × 10−3 and 3.7 × 10−3 were obtained at a 2.3 m underwater transmission distance using an on-off keying (OOK) modulation scheme, respectively. And the corresponding UWOC aggregate data rate of 9.7 Gbps was achieved based on RGB LDs-based wavelength-division multiplexing (WDM) UWOC. Moreover, UWOC and underwater SSL by using RGB LDs mixed white light were investigated at different scenarios over an underwater link of 2.3 m. The RGB LDs mixed white light-based UWOC system without optical diffusers yielded a maximum allowable data rate of 8.7 Gbps with Commission International de l’Eclairage coordinates (CIE) of (0.3154, 0.3354), a correlated color temperature of 6322 K, a color rendering index of 69.3 and a corresponding illuminance of 7084 lux. Furthermore, optical diffusers were employed to provide large-area underwater SSL. The LDs mixed white light-based UWOC system with line and circle optical diffusers implemented data rates of 5.9 Gbps and 6.6 Gbps with CIE coordinates of (0.3183, 0.3269) and (0.3298, 0.3390), respectively. This work suggests the potential of LDs for applications in high-efficiency underwater white-light SSL and high-speed UWOC.
- Published
- 2018
19. Realizing Wafer‐Scale and Low‐Voltage Operation MoS 2 Transistors via Electrolyte Gating
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Jianan Deng, Hu Xu, Zhi-Jun Qiu, Fuyou Liao, Wei Niu, Jing Chen, Wenzhong Bao, Hongwei Tang, Yong Pu, Haima Zhang, and Jing Wan
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Materials science ,Scale (ratio) ,Polymer electrolytes ,business.industry ,Transistor ,Gating ,Electrolyte ,Electronic, Optical and Magnetic Materials ,law.invention ,law ,Optoelectronics ,Field-effect transistor ,Wafer ,business ,Low voltage - Published
- 2019
20. Tuning of Schottky Barrier Height at NiSi/Si Contact by Combining Dual Implantation of Boron and Aluminum and Microwave Annealing
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Dongping Wu, Zhi-Jun Qiu, Jun Luo, Chen Li, Chaochao Fu, Xiangbiao Zhou, Feng Sun, and Wei Zou
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Materials science ,Silicon ,Annealing (metallurgy) ,Schottky barrier ,chemistry.chemical_element ,02 engineering and technology ,dual implantation ,01 natural sciences ,lcsh:Technology ,Article ,law.invention ,law ,0103 physical sciences ,General Materials Science ,Boron ,lcsh:Microscopy ,Diode ,lcsh:QC120-168.85 ,010302 applied physics ,Dopant ,lcsh:QH201-278.5 ,business.industry ,Schottky barrier height ,SB-MOSFET ,dopant segregation ,microwave annealing ,lcsh:T ,Transistor ,021001 nanoscience & nanotechnology ,Semiconductor ,chemistry ,lcsh:TA1-2040 ,Optoelectronics ,lcsh:Descriptive and experimental mechanics ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,0210 nano-technology ,business ,lcsh:Engineering (General). Civil engineering (General) ,lcsh:TK1-9971 - Abstract
Dopant-segregated source/drain contacts in a p-channel Schottky-barrier metal-oxide semiconductor field-effect transistor (SB-MOSFET) require further hole Schottky barrier height (SBH) regulation toward sub-0.1 eV levels to improve their competitiveness with conventional field-effect transistors. Because of the solubility limits of dopants in silicon, the requirements for effective hole SBH reduction with dopant segregation cannot be satisfied using mono-implantation. In this study, we demonstrate a potential solution for further SBH tuning by implementing the dual implantation of boron (B) and aluminum (Al) in combination with microwave annealing (MWA). By using such a method, not only has the lowest hole SBH ever with 0.07 eV in NiSi/n-Si contacts been realized, but also the annealing duration of MWA was sharply reduced to 60 s. Moreover, we investigated the SBH tuning mechanisms of the dual-implanted diodes with microwave annealing, including the dopant segregation, activation effect, and dual-barrier tuning effect of Al. With the selection of appropriate implantation conditions, the dual implantation of B and Al combined with the MWA technique shows promise for the fabrication of future p-channel SB-MOSFETs with a lower thermal budget.
- Published
- 2018
21. Layer thinning of MoS2 flakes by thermal annealing in air
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Zhi-Jun Qiu, Laigui Hu, Youwei Zhang, Pengfei Tian, Ran Liu, Chunxiao Cong, and Qiyuan Wang
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Fabrication ,Materials science ,business.industry ,Annealing (metallurgy) ,Force spectroscopy ,law.invention ,symbols.namesake ,Optical microscope ,law ,Microscopy ,Thermal ,Monolayer ,symbols ,Optoelectronics ,business ,Raman spectroscopy - Abstract
We successfully thinned multilayer MoS 2 flakes to monolayer by a simple and low-cost fabrication using thermal annealing in air. Optical microscopy, Raman microscopy and atomic force spectroscopy were used to characterize the process of thermal thinning. Our results demonstrate a satisfactory uniformity of annealed monolayer MoS 2 . This process might show advantages in fabrication of nano-electronic devices based on thermally thinned MoS 2 .
- Published
- 2017
22. Development and Evaluation of Adaptive Transit Signal Priority Control with Updated Transit Delay Model
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Amy Kim, Xu Han, Zhi-jun Qiu, Rajib Sikder, and Pengfei Li
- Subjects
Mathematical optimization ,business.industry ,Computer science ,Mechanical Engineering ,Reliability (computer networking) ,Real-time computing ,Context (language use) ,Traffic flow ,Public transport ,Key (cryptography) ,Bus priority ,business ,Intelligent transportation system ,Civil and Structural Engineering - Abstract
Transit signal priority (TSP) strategies are widely used to reduce bus travel delay and to increase bus service reliability. State-of-the-art strategies enable dynamic (and optimal), rather than predetermined, TSP plans to reflect real-time traffic conditions. These dynamic plans are called adaptive TSP. Existing adaptive TSP strategies normally use a performance index (PI), which is a weighted summation of all types of delays, to evaluate each candidate TSP plan and the weights to reflect the corresponding priority. The performance of an adaptive TSP depends on three factors: delay estimation, weights determination, and optimization formulation. In this context, there are three key academic contributions: (a) an enhanced bus delay estimation model based on advance detection, (b) a mechanism to adjust the PI weights dynamically to reflect the changing necessity of TSP under different conditions, and (c) TSP optimization formulated into a quadratic programming problem with an enhanced delay-based PI to obt...
- Published
- 2014
23. Wafer-scale transferred multilayer MoS2 for high performance field effect transistors
- Author
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Simeng Zhang, Zihan Xu, Zhengzong Sun, Zhi-Jun Qiu, Lin Chen, Hu Xu, Kun Ba, Yangye Sun, Fuyou Liao, Hao Zhu, Qing-Qing Sun, Wenzhong Bao, David Wei Zhang, and Peng Zhou
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Materials science ,business.industry ,Mechanical Engineering ,Stacking ,Bioengineering ,02 engineering and technology ,General Chemistry ,Semiconductor device ,Chemical vapor deposition ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Surface energy ,0104 chemical sciences ,Transition metal ,Mechanics of Materials ,Optoelectronics ,General Materials Science ,Field-effect transistor ,Wafer ,Electrical and Electronic Engineering ,0210 nano-technology ,business ,Layer (electronics) - Abstract
Chemical vapor deposition synthesis of semiconducting transition metal dichalcogenides (TMDs) offers a new route to build next-generation semiconductor devices. But realization of continuous and uniform multilayer (ML) TMD films is still limited by their specific growth kinetics, such as the competition between surface and interfacial energy. In this work, a layer-by-layer vacuum stacking transfer method is applied to obtain uniform and non-destructive ML-MoS2 films. Back-gated field effect transistor (FET) arrays of 1L- and 2L-MoS2 are fabricated on the same wafer, and their electrical performances are compared. We observe a significant increase of field-effect mobility for 2L-MoS2 FETs, up to 32.5 cm2 V-1 s-1, which is seven times higher than that of 1L-MoS2 (4.5 cm2 V-1 s-1). Then we also fabricated 1L-, 2L-, 3L-, and 4L-MoS2 FETs to further investigate the thickness-dependent characteristics of transferred ML-MoS2. Measurement results show a higher mobility but a smaller current on/off ratio as the layer number increases, suggesting that a balance between mobility and current on/off ratio can be achieved in 2L- and 3L-MoS2 FETs. Dual-gated structure is also investigated to demonstrate an improved electrostatic control of the ML-MoS2 channel.
- Published
- 2019
24. Solution-Processed Logic Gates Based On Nanotube/Polymer Composite
- Author
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Dongping Wu, Shi-Li Zhang, Zhiwei Zhu, Xindong Gao, Zhibin Zhang, Zhiying Liu, and Zhi-Jun Qiu
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Electron mobility ,Materials science ,business.industry ,Gate dielectric ,Transistor ,Nanotechnology ,Carbon nanotube ,Electronic, Optical and Magnetic Materials ,law.invention ,Hysteresis ,law ,Thin-film transistor ,Logic gate ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Electronic circuit - Abstract
Hysteresis-free logic gates capable of operation at 100 kHz are fabricated basing on local-gate thin-film transistors with their channel featuring solution-processed composite films of single-walled carbon nanotubes (SWCNTs) and poly(9,9-dioctylfluorene-co-bithiophene) (F8T2). Using dip-coating for deposition of composite films, high-density SWCNTs are found to be embedded in an F8T2 layer and thus being kept from the underlying AlOx gate dielectric by a certain distance. The presence of the F8T2 interlayer effectively suppresses hysteresis although it also weakens the gate electrostatic control. The fabricated transistors are characterized by nil hysteresis, high carrier mobility, large ON/OFF current ratio, low operation voltage, small subthreshold swing, and remarkable scalability. These properties are crucial for the realization of the well-performing logic circuits.
- Published
- 2013
25. Accelerating Gas Adsorption on 3D Percolating Carbon Nanotubes
- Author
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Hui Li, Zhi-Jun Qiu, Shi-Li Zhang, Dongping Wu, Youwei Zhang, and Chenyu Wen
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Materials science ,Composite number ,02 engineering and technology ,Carbon nanotube ,Electrical Engineering, Electronic Engineering, Information Engineering ,010402 general chemistry ,Bioinformatics ,01 natural sciences ,Article ,law.invention ,Condensed Matter::Materials Science ,Adsorption ,law ,Elektroteknik och elektronik ,Multidisciplinary ,business.industry ,Transistor ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Hysteresis ,Semiconductor ,Optoelectronics ,Field-effect transistor ,0210 nano-technology ,business ,Dispersion (chemistry) - Abstract
In the field of electronic gas sensing, low-dimensional semiconductors such as single-walled carbon nanotubes (SWCNTs) can offer high detection sensitivity owing to their unprecedentedly large surface-to-volume ratio. The sensitivity and responsivity can further improve by increasing their areal density. Here, an accelerated gas adsorption is demonstrated by exploiting volumetric effects via dispersion of SWCNTs into a percolating three-dimensional (3D) network in a semiconducting polymer. The resultant semiconducting composite film is evaluated as a sensing membrane in field effect transistor (FET) sensors. In order to attain reproducible characteristics of the FET sensors, a pulsed-gate-bias measurement technique is adopted to eliminate current hysteresis and drift of sensing baseline. The rate of gas adsorption follows the Langmuir-type isotherm as a function of gas concentration and scales with film thickness. This rate is up to 5 times higher in the composite than only with an SWCNT network in the transistor channel, which in turn results in a 7-fold shorter time constant of adsorption with the composite. The description of gas adsorption developed in the present work is generic for all semiconductors and the demonstrated composite with 3D percolating SWCNTs dispersed in functional polymer represents a promising new type of material for advanced gas sensors.
- Published
- 2016
26. Thickness Considerations of Two-Dimensional Layered Semiconductors for Transistor Applications
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Youwei Zhang, Zhi-Jun Qiu, Shi-Li Zhang, Hui Li, Xie Hong, Haomin Wang, and Ran Liu
- Subjects
Fabrication ,Materials science ,Silicon ,chemistry.chemical_element ,02 engineering and technology ,Conductivity ,Electrical Engineering, Electronic Engineering, Information Engineering ,01 natural sciences ,Article ,Ion ,law.invention ,law ,0103 physical sciences ,Elektroteknik och elektronik ,Scaling ,010302 applied physics ,Multidisciplinary ,business.industry ,Transistor ,Orders of magnitude (numbers) ,021001 nanoscience & nanotechnology ,Semiconductor ,chemistry ,Optoelectronics ,0210 nano-technology ,business - Abstract
Layered two-dimensional semiconductors have attracted tremendous attention owing to their demonstrated excellent transistor switching characteristics with a large ratio of on-state to off-state current, Ion/Ioff. However, the depletion-mode nature of the transistors sets a limit on the thickness of the layered semiconductor films primarily determined by a given Ion/Ioff as an acceptable specification. Identifying the optimum thickness range is of significance for material synthesis and device fabrication. Here, we systematically investigate the thickness-dependent switching behavior of transistors with a wide thickness range of multilayer-MoS2 films. A difference in Ion/Ioff by several orders of magnitude is observed when the film thickness, t, approaches a critical depletion width. The decrease in Ion/Ioff is exponential for t between 20 nm and 100 nm, by a factor of 10 for each additional 10 nm. For t larger than 100 nm, Ion/Ioff approaches unity. Simulation using technical computer-aided tools established for silicon technology faithfully reproduces the experimentally determined scaling behavior of Ion/Ioff with t. This excellent agreement confirms that multilayer-MoS2 films can be approximated as a homogeneous semiconductor with high surface conductivity that tends to deteriorate Ion/Ioff. Our findings are helpful in guiding material synthesis and designing advanced field-effect transistors based on the layered semiconductors.
- Published
- 2016
27. SMALL-Hysteresis Thin-Film Transistors Achieved by Facile Dip-Coating of Nanotube/Polymer Composite
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Shi-Li Zhang, Zhi-Jun Qiu, Zhibin Zhang, Hui Li, and Zhiying Liu
- Subjects
chemistry.chemical_classification ,Nanotube ,Materials science ,Transistors, Electronic ,Nanotubes, Carbon ,Polymers ,Surface Properties ,business.industry ,Mechanical Engineering ,Transistor ,Composite number ,Nanotechnology ,Polymer ,Carbon nanotube ,Silicon Dioxide ,Dip-coating ,law.invention ,Hysteresis ,chemistry ,Mechanics of Materials ,Thin-film transistor ,law ,Optoelectronics ,General Materials Science ,business - Abstract
Small-hysteresis, high-performance thin-film transistors (TFTs) are readily realized simply by dip-coating of a solution-processable composite. The composite consists of single-walled carbon nanotubes (SWCNTs) embedded in semiconducting polymer used as the channel material. The resultant TFTs simultaneously exhibit large on/off current ratio, high on-current level, high mobility in the range 10-20 cm(2)V(-1)s(-1), and good uniformity and scalability.
- Published
- 2012
28. On Different Process Schemes for MOSFETs With a Controllable NiSi-Based Metallic Source/Drain
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Dongping Wu, Mikael Östling, Jun Luo, Lars Hultman, Zhi-Jun Qiu, Shi-Li Zhang, and Jun Lu
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Materials science ,Annealing (metallurgy) ,business.industry ,Schottky barrier ,Transistor ,Silicon on insulator ,Electronic, Optical and Magnetic Materials ,law.invention ,Thin-film transistor ,law ,Logic gate ,MOSFET ,Electronic engineering ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Extrinsic semiconductor - Abstract
This paper focuses on different silicidation schemes toward a controllable NiSi-based metallic source/drain (MSD) process with restricted lateral encroachment of NiSi. These schemes include thickness control of Ni, Ni-Pt alloying, and two-step annealing. Experimental results show that all the three process schemes can give rise to effective control of lateral encroachment during Ni silicidation. By controlling tNi, NiSi-based MSD metal-oxide-semiconductor field-effect transistors (MOSFETs) of gate length LG = 55 nm are readily realized on ultrathin-body silicon-on-insulator substrates with 20-nm surface Si thickness. With the aid of dopant segregation (DS) to modifying the Schottky barrier heights of NiSi, both n- and p-type MSD MOSFETs show significant performance improvement, compared to reference devices without DS.
- Published
- 2011
29. Extending the Spectral Responsivity of MoS2 Phototransistors by Incorporating Up-Conversion Microcrystals
- Author
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Shi-Li Zhang, Jinhai Shao, Pengfei Tian, Jiao Wang, Jianan Deng, Youwei Zhang, Chunxiao Cong, Zhi-Jun Qiu, Bing Wang, Ran Liu, and Laigui Hu
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Materials science ,Spectral responsivity ,business.industry ,02 engineering and technology ,Photoelectric effect ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,Semiconductor ,chemistry ,Block (telecommunications) ,Optoelectronics ,Up conversion ,0210 nano-technology ,business ,Molybdenum disulfide - Abstract
Layered 2D semiconductors are characterized by unique photoelectric properties and, therefore, constitute a new class of basic building block for next‐generation optoelectronics. However, their wid ...
- Published
- 2018
30. Competing Mechanisms for Photocurrent Induced at the Monolayer-Multilayer Graphene Junction
- Author
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Pengfei Tian, Shi-Li Zhang, Ran Liu, Zhi-Jun Qiu, Laigui Hu, Hemei Zheng, Youwei Zhang, Chunxiao Cong, and Qiyuan Wang
- Subjects
Photocurrent ,Materials science ,Terahertz radiation ,business.industry ,Graphene ,Dirac (software) ,Heterojunction ,02 engineering and technology ,General Chemistry ,Photodetection ,Photovoltaic effect ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,Biomaterials ,law ,0103 physical sciences ,Monolayer ,Optoelectronics ,General Materials Science ,010306 general physics ,0210 nano-technology ,business ,Biotechnology - Abstract
Graphene is characterized by demonstrated unique properties for potential novel applications in photodetection operated in the frequency range from ultraviolet to terahertz. To date, detailed work on identifying the origin of photoresponse in graphene is still ongoing. Here, scanning photocurrent microscopy to explore the nature of photocurrent generated at the monolayer-multilayer graphene junction is employed. It is found that the contributing photocurrent mechanism relies on the mismatch of the Dirac points between the monolayer and multilayer graphene. For overlapping Dirac points, only photothermoelectric effect (PTE) is observed at the junction. When they do not coincide, a different photocurrent due to photovoltaic effect (PVE) appears and becomes more pronounced with larger separation of the Dirac points. While only PTE is reported for a monolayer-bilayer graphene junction in the literature, this work confirms the coexistence of PTE and PVE, thereby extending the understanding of photocurrent in graphene-based heterojunctions.
- Published
- 2018
31. Large-signal modulation characteristics of a GaN-based micro-LED for Gbps visible-light communication
- Author
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Ming-Gang Liu, Chia-Yu Lee, Zhilai Fang, Xiaolin Zhou, Kefu Liu, Laigui Hu, Xiaoyan Liu, Ran Liu, Zhi-Jun Qiu, Pengfei Tian, Zhengyuan Wu, Shu-Jhih Chen, Chunxiao Cong, Shuailong Zhang, and Lirong Zheng
- Subjects
020210 optoelectronics & photonics ,Materials science ,business.industry ,Signal modulation ,0202 electrical engineering, electronic engineering, information engineering ,General Engineering ,General Physics and Astronomy ,Visible light communication ,Optoelectronics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,0210 nano-technology ,business - Published
- 2018
32. Effects of UV-Ozone Treatment on Sensing Behaviours of EGFETs with Al2O3 Sensing Film
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Dongping Wu, Zhi-Jun Qiu, Junkai Zhang, Ruixue Zeng, and Cuiling Sun
- Subjects
Yield (engineering) ,Materials science ,02 engineering and technology ,lcsh:Technology ,01 natural sciences ,Article ,Surface conditions ,Uv ozone ,X-ray photoelectron spectroscopy ,UV-ozone ,EGFETs ,Al2O3 ,General Materials Science ,lcsh:Microscopy ,lcsh:QC120-168.85 ,lcsh:QH201-278.5 ,lcsh:T ,business.industry ,Atomic force microscopy ,010401 analytical chemistry ,pH sensing ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,instability ,Hysteresis ,lcsh:TA1-2040 ,Optoelectronics ,Degradation (geology) ,lcsh:Descriptive and experimental mechanics ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,Treatment time ,lcsh:Engineering (General). Civil engineering (General) ,0210 nano-technology ,business ,lcsh:TK1-9971 - Abstract
The effects of UV-ozone (UVO) treatment on the sensing behaviours of extended-gate field-effect transistors (EGFETs) that use Al2O3 as the sensing film have been investigated. The Al2O3 sensing films are UVO-treated with various duration times and the corresponding EGFET sensing behaviours, such as sensitivity, hysteresis, and long-term stability, are electrically evaluated under various measurement conditions. Physical analysis is also performed to characterize the surface conditions of the UVO-treated sensing films using X-ray photoelectron spectroscopy and atomic force microscopy. It is found that UVO treatment effectively reduces the buried sites in the Al2O3 sensing film and subsequently results in reduced hysteresis and improved long-term stability of EGFET. Meanwhile, the observed slightly smoother Al2O3 film surface post UVO treatment corresponds to decreased surface sites and slightly reduced pH sensitivity of the Al2O3 film. The sensitivity degradation is found to be monotonically correlated with the UVO treatment time. A treatment time of 10 min is found to yield an excellent performance trade-off: clearly improved long-term stability and reduced hysteresis at the cost of negligible sensitivity reduction. These results suggest that UVO treatment is a simple and facile method to improve the overall sensing performance of the EGFETs with an Al2O3 sensing film.
- Published
- 2017
33. A real-time Raman spectroscopy study of the dynamics of laser-thinning of MoS2 flakes to monolayers
- Author
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Chunxiao Cong, Qiyuan Wang, Shi-Li Zhang, Laigui Hu, Pengfei Tian, Youwei Zhang, Zhi-Jun Qiu, Enyao Gu, and Ran Liu
- Subjects
Void (astronomy) ,Nanoteknik ,Materials science ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,law.invention ,symbols.namesake ,law ,Monolayer ,Empirical formula ,Irradiation ,Laser power scaling ,business.industry ,021001 nanoscience & nanotechnology ,Laser ,lcsh:QC1-999 ,0104 chemical sciences ,symbols ,Optoelectronics ,Nano Technology ,Sublimation (phase transition) ,0210 nano-technology ,Raman spectroscopy ,business ,lcsh:Physics - Abstract
Transition metal dichalcogenides (TMDCs) in monolayer form have attracted a great deal of attention for electronic and optical applications. Compared to mechanical exfoliation and chemical synthesis, laser thinning is a novel and unique “on-demand” approach to fabricate monolayers or pattern desired shapes with high controllability and reproducibility. Its successful demonstration motivates a further exploration of the dynamic behaviour of this local thinning process. Here, we present an in-situ study of void formation by laser irradiation with the assistance of temporal Raman evolution. In the analysis of time-dependent Raman intensity, an empirical formula relating void size to laser power and exposure time is established. Void in thinner MoS2 flakes grows faster than in thicker ones as a result of reduced sublimation temperature in the two-dimensional (2D) materials. Our study provides useful insights into the laser-thinning dynamics of 2D TMDCs and guidelines for an effective control over the void formation.
- Published
- 2017
34. Laser-scribed highly responsive infrared detectors with semi-reduced graphene oxide
- Author
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Jing Chen, Youwei Zhang, Laigui Hu, Rui Feng, Qingmiao Nie, Pengfei Tian, Chunxiao Cong, Muhammad Zaheer, Wei Jin, Ran Liu, and Zhi-Jun Qiu
- Subjects
Materials science ,Infrared ,Graphene ,business.industry ,Transistor ,Gate dielectric ,General Engineering ,General Physics and Astronomy ,Photodetector ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,0104 chemical sciences ,law.invention ,Responsivity ,law ,Optoelectronics ,0210 nano-technology ,business ,Dark current - Abstract
Graphene-based optoelectronic devices, including reduced graphene oxide (RGO) devices, commonly exhibit a large dark current and low on/off ratio with high dark-power consumption and a small responsivity. In this study, semi-RGO-based infrared photodetectors were directly "written" by using lasers, which can exhibit a small dark current of approximately 12 µA/cm2 with a high responsivity of approximately 0.18 A/W at 1,550 nm. Both the dark current and response speed can be tuned with GO as the gate dielectric in a field-effect transistor structure. These findings suggest the possibility of the three-dimensional "writing" of a micro-optoelectronic device or system with a low cost and high performance.
- Published
- 2017
35. 345 m underwater optical wireless communication with 270 Gbps data rate based on a green laser diode with NRZ-OOK modulation
- Author
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Chunxiao Cong, Xiaoyan Liu, Xiaolin Zhou, Zhilai Fang, Ran Liu, Suyu Yi, Laigui Hu, Zhi-Jun Qiu, Li-Rong Zheng, and Pengfei Tian
- Subjects
Physics ,business.industry ,On-off keying ,Keying ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,010309 optics ,Optics ,Transmission (telecommunications) ,Modulation ,0103 physical sciences ,Underwater ,0210 nano-technology ,business ,Quadrature amplitude modulation ,Diode ,Beam divergence - Abstract
To enable high-speed long-distance underwater optical wireless communication (UOWC) supplementing traditional underwater wireless communication, a low-power 520 nm green laser diode (LD) based UOWC system was proposed and experimentally demonstrated to implement maximal communication capacity of up to 2.70 Gbps data rate over a 34.5 m underwater transmission distance by using non-return-to-zero on-off keying (NRZ-OOK) modulation scheme. Moreover, maximum data rates of up to 4.60 Gbps, 4.20 Gbps, 3.93 Gbps, 3.88 Gbps, and 3.48 Gbps at underwater distances of 2.3 m, 6.9 m, 11.5 m, 16.1 m and 20.7 m were achieved, respectively. The light attenuation coefficient of ~0.44 dB/m was obtained and the beam divergence angle is 0.35°, so the aallowable underwater transmission distance can be estimated to be ~90.7 m at a data rate of 0.15 Gbps with a corresponding received light-output power of -33.01 dBm and a bit-error rate (BER) of 2.0 ×10-6. In addition, when the data rate is up to 1 Gbps, the UOWC distance is predicted to be ~62.7 m for our proposed UOWC system. The achievements we make are suitable for applications requiring high-speed long-distance real-time UOWC.
- Published
- 2017
36. Photothermoelectric and photovoltaic effects both present in MoS2
- Author
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Hui-Hui Li, Xiaomin Xie, Shi-Li Zhang, Lu Wang, Zhi-Jun Qiu, Ran Liu, Youwei Zhang, and Haomin Wang
- Subjects
Thermal equilibrium ,Photocurrent ,Other Engineering and Technologies ,Multidisciplinary ,Computer science ,business.industry ,Graphene ,Transistor ,Photovoltaic system ,Photodetector ,Photovoltaic effect ,Bioinformatics ,Article ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Seebeck coefficient ,Monolayer ,Optoelectronics ,Annan teknik ,business ,Molybdenum disulfide - Abstract
As a finite-energy-bandgap alternative to graphene, semiconducting molybdenum disulfide (MoS2) has recently attracted extensive interest for energy and sensor applications. In particular for broad-spectral photodetectors, multilayer MoS2 is more appealing than its monolayer counterpart. However, little is understood regarding the physics underlying the photoresponse of multilayer MoS2. Here, we employ scanning photocurrent microscopy to identify the nature of photocurrent generated in multilayer MoS2 transistors. The generation and transport of photocurrent in multilayer MoS2 are found to differ from those in other low-dimensional materials that only contribute with either photovoltaic effect (PVE) or photothermoelectric effect (PTE). In multilayer MoS2, the PVE at the MoS2-metal interface dominates in the accumulation regime whereas the hot-carrier-assisted PTE prevails in the depletion regime. Besides, the anomalously large Seebeck coefficient observed in multilayer MoS2, which has also been reported by others, is caused by hot photo-excited carriers that are not in thermal equilibrium with the MoS2 lattice.
- Published
- 2015
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37. Anti-Stokes Photoluminescence of van der Waals Layered Semiconductor PbI2
- Author
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Shun Feng, Chenji Zou, Lin Niu, Yu Chen, Lishu Wu, Jingzhi Shang, Chunxiao Cong, Zhi-Jun Qiu, Zheng Liu, Ting Yu, Pengfei Tian, Laigui Hu, and Ran Liu
- Subjects
Photoluminescence ,Materials science ,Thin layers ,business.industry ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,symbols.namesake ,Semiconductor ,Photovoltaics ,symbols ,Optoelectronics ,Direct and indirect band gaps ,van der Waals force ,0210 nano-technology ,business ,Lasing threshold ,Perovskite (structure) - Abstract
Recently, organic–inorganic lead iodide perovskite has become one of the most promising emergent materials, which exhibits great potential in photovoltaics, lasing, laser cooling, etc. The building block of such great material is PbI2, a van der Waals (vdW) layered semiconductor material, which arouses increased interest also owing to its potential applications for X-ray and γ-ray detection, lasing, etc. Similar and even superior to some vdW layered materials such as thin layers of transition metal dichalcogenides like MoS2, WS2, MoSe2, or WSe2, PbI2 layers possess a direct bandgap of visible frequency with a wide range of thicknesses (>3 layers). This study reports the anti-Stokes photoluminescence (ASPL) of PbI2 layers, which is very rarely investigated at present. Universe and robust ASPL in both 4H- and 2H-PbI2 layers are observed and a phonon-assisted and multiphoton absorption up-conversion mechanisms are proposed through in situ temperature-dependent, incident laser-power-dependent measurements of both Stokes photoluminescence and ASPL. The successful observation and explanation of the universal anti-Stokes emission of PbI2 layers, will certainly enrich fundamental understandings of vdW layered semiconductors and perovskite, then further benefit to developing applications based on such emerging materials.
- Published
- 2017
38. Characteristics of GaN-based light emitting diodes with different thicknesses of buffer layer grown by HVPE and MOCVD
- Author
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Jonathan J. D. McKendry, Robert W. Martin, Chuanyu Jia, Martin D. Dawson, Ran Liu, Erdan Gu, Guoyi Zhang, Lirong Zheng, Zhizhong Chen, Paul R. Edwards, Zhi-Jun Qiu, Michael J. Wallace, and Pengfei Tian
- Subjects
010302 applied physics ,Materials science ,Photoluminescence ,Acoustics and Ultrasonics ,business.industry ,Cathodoluminescence ,02 engineering and technology ,Electroluminescence ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Epitaxy ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,QC350 ,Solid-state lighting ,law ,0103 physical sciences ,Optoelectronics ,Metalorganic vapour phase epitaxy ,0210 nano-technology ,business ,Quantum well ,Light-emitting diode - Abstract
GaN-based light emitting diodes (LEDs) have been fabricated on sapphire substrates with different thicknesses of GaN buffer layer grown by a combination of hydride vapor phase epitaxy and metalorganic chemical vapor deposition. We analyzed the LED efficiency and modulation characteristics with buffer thicknesses of 12 µm and 30 µm. With the buffer thickness increase, cathodoluminescence hyperspectral imaging shows that the dislocation density in the buffer layer decreases from ∼1.3X10 8 cm-2 to∼1.0 X 10 8 cm-2, and Raman spectra suggest that the compressive stress in the quantum wells is partly relaxed, which leads to a large blue shift in the peak emission wavelength of the photoluminescence and electroluminescent spectra. The combined effects of the low dislocation density and stress relaxation lead to improvements in the efficiency of LEDs with the 30 µm GaN buffer, but the electrical-to-optical modulation bandwidth is higher for the LEDs with the 12 µm GaN buffer. A rate equation analysis suggests that defect-related nonradiative recombination can help increase the modulation bandwidth but reduce the LED efficiency at low currents, suggesting that a compromise should be made in the choice of defect density.
- Published
- 2017
39. Mobility Extraction for Nanotube TFTs
- Author
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Zhiying Liu, Zhi-Jun Qiu, Zhibin Zhang, Li-Rong Zheng, and Shi-Li Zhang
- Subjects
Nanotube ,Electron mobility ,Materials science ,business.industry ,Transistor ,Hardware_PERFORMANCEANDRELIABILITY ,Carbon nanotube ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Capacitance ,Electronic, Optical and Magnetic Materials ,law.invention ,Condensed Matter::Materials Science ,Semiconductor ,law ,Thin-film transistor ,MOSFET ,Hardware_INTEGRATEDCIRCUITS ,Electronic engineering ,Optoelectronics ,Electrical and Electronic Engineering ,business - Abstract
An extensive investigation of carrier mobility is presented for thin-film transistors (TFTs) with single-walled carbon nanotube (SWCNT) networks as the semiconductor channel. For TFTs particularly with low-density SWCNTs in the networks, the extracted mobility using the standard method for Si metal-oxide-semiconductor field-effect transistors is erroneous, mainly resulting from use of a parallel-plate capacitor model and assumption of the source-drain current being inversely proportional to the channel length. Large hysteresis in the transfer characteristics further complicates the extraction. By properly addressing all these challenges in this letter, a comprehensive methodology is established, leading to the extraction of mobility values that are independent of geometrical parameters.
- Published
- 2011
40. Influences of embossing technology on Pb(Zr0.3,Ti0.7)O3 ferroelectric thin film
- Author
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Zhihui Chen, Zhi-Jun Qiu, Yifang Chen, Jing Wan, Bing-Rui Lu, Anquan Jiang, Zhenkui Shen, Shaoren Deng, Ran Liu, and Xin-Ping Qu
- Subjects
Nanostructure ,Materials science ,business.industry ,Scanning electron microscope ,Integrated circuit ,Condensed Matter Physics ,Ferroelectricity ,Atomic and Molecular Physics, and Optics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,Non-volatile memory ,law ,Ferroelectric thin films ,Optoelectronics ,Electrical and Electronic Engineering ,Thin film ,business ,Embossing - Abstract
The ferroelectric random access memory (FRAM) which uses ferroelectric thin film as memory material is considered to be a candidate for the next generation memory application. In this work, we apply nano-embossing technology to fabricate Pb(Zr"0"."3,Ti"0"."7)O"3 (PZT) ferroelectric thin film nanostructures and investigate the influence of the patterning process on the material and ferroelectric properties by using SEM, XRD and Precision Ferroelectric Tester. Embossing process has been optimized for embossing depth and pattern profile. It was found that embossing will result in (100) preferred orientation of the PZT thin film. The electrical characteristics of patterned and un-patterned PZT films have been also studied for comparison.
- Published
- 2010
41. Research of EEG from Patients with Temporal Lobe Epilepsy on Causal Analysis of Directional Transfer Functions
- Author
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Xin Tian, Hong-yan Zhang, and Zhi-jun Qiu
- Subjects
medicine.medical_specialty ,medicine.diagnostic_test ,business.industry ,Electroencephalography ,Audiology ,medicine.disease ,Causality ,Temporal lobe ,Functional imaging ,Epilepsy ,Eeg data ,Right posterior ,Medicine ,Artificial intelligence ,business ,Causal analysis - Abstract
Objective: 16-channel EEG data during intermittent episodes of epilepsy is recoded and analyzed to find lesions source and relationship between brain areas for temporal lobe epilepsy (TLE) patients by causal analysis method. Methods: There are 8 patients with temporal lobe epilepsy, 5 males and 3 females, aged between 19 to 47 years, the average age of 30.63 years. 16-channel EEG in 8 patients was recorded by Stellate Video EEG. Sample time = 20s (sample points = 4000), Sampling frequency fs = 2 0 0 Hz. Directional transfer functions is used to direct the information transduction between each channel of the EEG signals, which can reflect the causal relationship between each channel and determine the location of the lesions source. (In this paper, we used eConnectome software that developed by Biomedical Functional Imaging and Neuroengineering Laboratory at the University of Minnesota, directed by Dr. Bin He). Results: Causality results of 8 patients during intermittent episodes of EEG 20s are as follows: 6 patients' lesions source are located on channels T5 and F7 in left tempora, One of 5 cases' are located on channel T5 in the left posterior temporal, One of 1 case is located on channel F7 in the left anterior temporal. And 2 patients' lesions source are located on channels T4 and T6 in the right tempora, in the 2 patients, 1 case's lesions source is located on channel T4 in right middle temporal, 1 case's lesions source is located on channel T6 in right posterior temporal. Causality results consistent with the clinical diagnosis. Conclusions: Research of EEG on causal analysis of directional transfer function can effectively determine the lesions source of seizure, and effectively calculate the transmission direction of the multi-channel information, which is to provide support in the clinic for determine the source of seizure.
- Published
- 2011
42. Thermal Stability and Dopant Segregation for Schottky Diodes With Ultrathin Epitaxial NiSi(2-y)
- Author
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Dapeng Chen, Shi-Li Zhang, Zhi-Jun Qiu, Jun Lu, Jun Luo, Dongping Wu, Xindong Gao, Lars Hultman, Chao Zhao, and Junfeng Li
- Subjects
Materials science ,Dopant ,NiSi(2) ,Annealing (metallurgy) ,business.industry ,Schottky barrier ,epitaxy ,Schottky diode ,Electron ,morphological stability ,Epitaxy ,Electronic, Optical and Magnetic Materials ,Schottky barrier height (SBH) ,Lattice (order) ,Teknik och teknologier ,Electronic engineering ,Optoelectronics ,Engineering and Technology ,Thermal stability ,Electrical and Electronic Engineering ,business ,ultrathin ,Dopant segregation (DS) - Abstract
The Schottky barrier height (SBH) of an ultrathin epitaxial NiSi(2-y) film grown on Si(100) is modified significantly by means of dopant segregation (DS). The DS process begins with the NiSi(2-y) formation and is followed by dopant implantation and drive-in annealing. The rapid lattice restoration and superior morphological stability upon heat treatment up to 800 degrees C allow the epitaxial NiSi(2-y) film to take full advantage of the DS process. For drive-in annealing below 750 degrees C, the effective SBH is altered to similar to 0.9-1 eV for both electrons and holes by B-DS and As-DS, respectively, without deteriorating the integrity of the NiSi(2-y) film. ©2011 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Jun Luo, Xindong Gao, Zhi-Jun Qiu, Jun Lu, Dongping Wu, Chao Zhao, Junfeng Li, Dapeng Chen, Lars Hultman and Shi-Li Zhang, Thermal Stability and Dopant Segregation for Schottky Diodes With Ultrathin Epitaxial NiSi(2-y), 2011, IEEE Electron Device Letters, (32), 8, 1029-1031.
- Published
- 2011
43. On gate capacitance of nanotube networks
- Author
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Shi-Li Zhang, Zhiying Liu, Zhi-Jun Qiu, Li-Rong Zheng, Zhibin Zhang, and Jiantong Li
- Subjects
Electron mobility ,Nanotube ,Materials science ,business.industry ,Nanotechnology ,Carbon nanotube ,transmission line model ,Capacitance ,Electronic, Optical and Magnetic Materials ,law.invention ,Frequency dependence ,percolation ,law ,Thin-film transistor ,Percolation ,Logic gate ,nanotube networks ,Teknik och teknologier ,MOSFET ,Optoelectronics ,Engineering and Technology ,Electrical and Electronic Engineering ,business ,gate capacitance - Abstract
This letter presents a systematic investigation of the gate capacitance CGof thin-film transistors (TFTs) based on randomly distributed single-walled carbon nanotubes (SWCNTs) in the channel. In order to reduce false counting of SWCNTs that do not contribute to current conduction, CG is directly measured on the TFTs using a well-established method for MOSFETs. Frequency dispersion of CG is observed, and it is found to depend on the percolation behavior in SWCNT networks. This dependence can be accounted for using an RC transmission line model. These results are of important implications for the determination of carrier mobility in nanoparticle-based TFTs. © 2011 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.QC 20120214 VINNOVA “iPack Vinnex Excellence Center” VR 2009-8068
- Published
- 2011
44. Quantum-mechanical study on the electron effective mobility of surrounding-gate nMOSFETs
- Author
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Lingli Wang, Guangxi Hu, Tingao Tang, Zhi-Jun Qiu, and Ran Liu
- Subjects
Electron mobility ,Materials science ,business.industry ,Transistor ,Electron ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Capacitance ,law.invention ,Computer Science::Hardware Architecture ,Semiconductor ,law ,Logic gate ,MOSFET ,Electronic engineering ,Optoelectronics ,Field-effect transistor ,business - Abstract
As metal - oxide - semiconductor field-effect transistors (MOSFETs) down scaling progresses into the nanometer regime, quantum mechanical effects are becoming more and more significant. In this work, a model for the surrounding-gate (SG) nMOSFET is developed. The Schrodinger equation is solved analytically and some of the results are verified via simulations. We find that the percentage of the electrons with a lighter conductivity mass increases as the temperature decreases, or as the gate voltage reduces. These imply that low temperature and low gate voltage will enhance the electron effective mobility, which is good for the device performance.
- Published
- 2009
45. Direct growth of high-quality Al2O3 dielectric on graphene layers by low-temperature H2O-based ALD
- Author
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Youwei Zhang, Haomin Wang, Zhi-Jun Qiu, Xie Hong, Yuehui Yu, Xiaomin Xie, Xinhong Cheng, and Ran Liu
- Subjects
Materials science ,Acoustics and Ultrasonics ,business.industry ,Graphene ,Graphene foam ,Nanotechnology ,Dielectric ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,Atomic layer deposition ,law ,Optoelectronics ,Thin film ,business ,Bilayer graphene ,Graphene nanoribbons ,Graphene oxide paper - Abstract
A thin Al2O3 dielectric film was directly grown onto graphene layers without any surface treatment prior to H2O-based atomic layer deposition for the first time. The growth mechanism of Al2O3 dielectric film has been studied by changing the growth temperature and purge time. We found that the film morphology was influenced by the amount and distribution of physically adsorbed precursor molecules on the graphene, especially by physically adsorbed H2O molecules. Within an optimal temperature window, conformal and uniform Al2O3 thin films were obtained as confirmed by atomic force microscopy and transmission electron microscopy results. Raman spectroscopy revealed that no extra defects are generated in the graphene layers. Furthermore, the low leakage current and interface traps in dual-gated graphene field-effect transistors demonstrate the high-quality dielectric/graphene stack.
- Published
- 2014
46. Nano-embossing technology on ferroelectric thin film Pb(Zr0.3,Ti0.7)O3 for multi-bit storage application
- Author
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Zhihui Chen, Zhenkui Shen, Yifang Chen, Qian Lu, Ran Liu, Zhi-Jun Qiu, Anquan Jiang, and Xin-Ping Qu
- Subjects
Materials science ,Nano Express ,business.industry ,Nanochemistry ,Nanotechnology ,Lead zirconate titanate ,Condensed Matter Physics ,Ferroelectricity ,Ferroelectric capacitor ,chemistry.chemical_compound ,Piezoresponse force microscopy ,chemistry ,Materials Science(all) ,Nano ,Optoelectronics ,General Materials Science ,business ,Embossing ,Voltage - Abstract
In this work, we apply nano-embossing technique to form a stagger structure in ferroelectric lead zirconate titanate [Pb(Zr0.3, Ti0.7)O3 (PZT)] films and investigate the ferroelectric and electrical characterizations of the embossed and un-embossed regions, respectively, of the same films by using piezoresponse force microscopy (PFM) and Radiant Technologies Precision Material Analyzer. Attributed to the different layer thickness of the patterned ferroelectric thin film, two distinctive coercive voltages have been obtained, thereby, allowing for a single ferroelectric memory cell to contain more than one bit of data.
- Published
- 2011
47. Characterizations of nanoembossed Pb(Zr0.3,Ti0.7)O3 ferroelectric films
- Author
-
Zhihui Chen, Xin-Ping Qu, Zhenkui Shen, Ran Liu, Zhi-Jun Qiu, Qian Lu, Anquan Jiang, and Yifang Chen
- Subjects
Diffraction ,Materials science ,business.industry ,Process Chemistry and Technology ,Ferroelectric ceramics ,Nanotechnology ,Piezoelectricity ,Ferroelectricity ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,symbols.namesake ,Nanolithography ,Piezoresponse force microscopy ,X-ray crystallography ,Materials Chemistry ,symbols ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Raman spectroscopy ,Instrumentation - Abstract
Ferroelectric thin films may find potential applications in a broad range of ferroelectronic devices such as mass-storage memories. In this article, arrays of Pb(Zr0.3,Ti0.7)O3 (PZT) ferroelectric cells with minimum lateral size down to 500 nm were fabricated by nanoembossing technique. Structural characterizations of embossed PZT film were carried out by Raman spectroscopy and x-ray diffraction. Ferroelectronic properties of embossed PZT film were investigated by using piezoresponse force microscopy and Radiant Technologies precision material analyzer. Excellent ferroelectric and piezoelectric characteristics observed in the embossed PZT films suggest that the nanoembossing process proposed in this article is promising to become a new manufacturing approach for high density PZT based memory devices at significantly lower cost than the existing technique.
- Published
- 2010
48. Interaction of NiSi with dopants for metallic source/drain applications
- Author
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Jun Luo, Shi-Li Zhang, Zhen Zhang, Mikael Östling, and Zhi-Jun Qiu
- Subjects
Materials science ,Passivation ,Dopant ,Silicon ,business.industry ,Band gap ,Process Chemistry and Technology ,Schottky barrier ,chemistry.chemical_element ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ion implantation ,chemistry ,Materials Chemistry ,Optoelectronics ,Work function ,Field-effect transistor ,Electrical and Electronic Engineering ,business ,Instrumentation - Abstract
This work has a focus on NiSi as a possible metallic contact for aggressively scaled complementary metal oxide semiconductor devices. As the bulk work function of NiSi lies close to the middle of Si bandgap, the Schottky barrier height (SBH) of NiSi is rather large for both electron (∼0.65eV) and hole (∼0.45eV). Different approaches have therefore been intensively investigated in the literature aiming at reducing the effective SBH: dopant segregation (DS), surface passivation (SP), and alloying, in order to improve the carrier injection into the conduction channel of a field-effect transistor. The present work explores DS using B and As for the NiSi∕Si contact system. The effects of C and N implantation into Si substrate prior to the NiSi formation are examined, and it is found that the presence of C yields positive effects in helping reduce the effective SBH to 0.1–0.2eV for both conduction polarities. A combined use of DS or SP with alloying could be considered for more effective control of effective SB...
- Published
- 2010
49. Investigate the feasibility of traffic speed estimation using cell phones as probes
- Author
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Bin Ran, Peng Cheng, and Zhi Jun Qiu
- Subjects
business.industry ,Computer science ,Real-time computing ,Floating car data ,Management Science and Operations Research ,Field (computer science) ,Computer Science Applications ,Management Information Systems ,Software deployment ,Phone ,Global Positioning System ,Cellular network ,Wireless ,Traffic speed ,business ,Simulation ,Information Systems - Abstract
These days Wireless Location Technology (WLT) develops very fast. The accuracy of mobile location has been remarkably improved, which provides the possibility of using cellular probes to give a fairly good estimate of travel speed or travel time in an urban region. Probe-based traffic monitoring system using cellular technology has much lower cost than the traditional method using Global Positioning System (GPS) and it can improve the utilisation of the existing facilities. This paper summarises several previous studies and field tests, analyses the raw cell phone data from one wireless carrier and tries to address the potential issues and feasible additional refinement for the future field deployment and operational application.
- Published
- 2007
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