26 results on '"Zhisheng Shi"'
Search Results
2. Enhanced CO2 hydrogenation to methanol over TiO2 nanotubes-supported CuO-ZnO-CeO2 catalyst
- Author
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Dongfang Wu, Zhisheng Shi, and Qingqing Tan
- Subjects
Morphology (linguistics) ,010405 organic chemistry ,Chemistry ,Process Chemistry and Technology ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Metal ,chemistry.chemical_compound ,Chemical engineering ,visual_art ,Specific surface area ,visual_art.visual_art_medium ,Methanol ,Selectivity ,Dispersion (chemistry) ,Porosity - Abstract
TiO2 nanotubes (TNTs) have been extensively applied in many fields owing to their excellent porous structure and surface properties. Herein, a series of CuO-ZnO-CeO2/TNTs catalysts are synthesized through a deposition-precipitation method. The effects of TNTs content and support morphology on the catalyst physicochemical properties and catalytic performance are investigated. The incorporation of TNTs support into CuO-ZnO-CeO2 catalysts not only promotes CuO reducibility and improves the metallic Cu dispersion and specific surface area, but also enhances CO2 adsorption and increases the proportion of basic sites γ, thereby resulting in high CO2 conversion and CH3OH selectivity. It is also shown that CO2 conversion is positively correlated with the Cu specific surface area and that CH3OH selectivity is related to the proportion of basic sites γ. Due to the excellent reducibility, high metallic Cu surface area, superior CO2 adsorption and large proportion of basic sites γ, CuO-ZnO-CeO2/10 wt.% TNTs gives excellent catalytic performance and possesses a great potential as catalyst for methanol synthesis.
- Published
- 2019
3. Growth Study of New Complex Oxide PbOxSe1–x Thin Films by Oxygen Plasma-Assisted Molecular Beam Epitaxy
- Author
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Lance L. McDowell, Binbin Weng, Jijun Qiu, and Zhisheng Shi
- Subjects
Materials science ,Absorption spectroscopy ,010405 organic chemistry ,Analytical chemistry ,General Chemistry ,010402 general chemistry ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,symbols.namesake ,Lattice constant ,chemistry ,Absorption edge ,Ternary compound ,symbols ,General Materials Science ,Crystallite ,Thin film ,Raman spectroscopy ,Molecular beam epitaxy - Abstract
In this work, we introduce the growth of a new complex oxide lead oxy-chalcogenide (PbOxSe1–x) thin film using an oxygen plasma-assisted molecular beam epitaxy method. Freshly cleaved BaF2(111) wafers were used as the substrates for this growth study. Systematic characterization of X-ray diffraction peaks, Raman shifts, absorption spectra, scanning electron microscopic imaging, and Hall measurements were conducted to elucidate the structural, optical, and electric properties of the as-grown PbOxSe1–x thin films. Specifically, X-ray diffraction measurements revealed that PbOxSe1–x films maintained the same rock-salt crystal structure as the PbSe semiconductor, but a slight shift in the lattice parameter was observed. A blue shift in the optical absorption edge also suggests that the inclusion of oxygen atoms led to the formation of a ternary compound crystal structure. Furthermore, all PbOxSe1–x thin films were observed to be polycrystalline in nature and displayed preferred [100] orientated grains. Slight...
- Published
- 2019
4. A novel Core–Shell structured CuIn@SiO 2 catalyst for CO 2 hydrogenation to methanol
- Author
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Dongfang Wu, Zhisheng Shi, and Qingqing Tan
- Subjects
Environmental Engineering ,Materials science ,010405 organic chemistry ,General Chemical Engineering ,010402 general chemistry ,01 natural sciences ,Oxygen vacancy ,0104 chemical sciences ,Catalysis ,Core shell ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Methanol ,Biotechnology - Published
- 2018
5. Reduction for heavy metals in pickling sludge with aluminum nitride in secondary aluminum dross by pyrometallurgy, followed by glass ceramics manufacture
- Author
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Zhisheng Shi, Junjie Zhang, Shizhen Zhao, Hanlin Shen, Shengen Zhang, and Bo Liu
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021110 strategic, defence & security studies ,Environmental Engineering ,Materials science ,Health, Toxicology and Mutagenesis ,Dross ,Metallurgy ,0211 other engineering and technologies ,chemistry.chemical_element ,02 engineering and technology ,010501 environmental sciences ,Nitride ,01 natural sciences ,Pollution ,Chromium ,chemistry ,Aluminium ,visual_art ,Pickling ,Pyrometallurgy ,visual_art.visual_art_medium ,Environmental Chemistry ,Ceramic ,Waste Management and Disposal ,0105 earth and related environmental sciences ,Solid solution - Abstract
Secondary aluminum dross (SAD) from aluminum industry is classified as a hazardous solid waste due to containing aluminum nitride (AlN). In this work, AlN was first used to reduce heavy metals by pyrometallurgy. The reduction rates for iron, chromium and nickel were up to 90%, 80% and 100%, respectively. However, the reduction from AlN and oxygen oxidization of AlN occurred simultaneously. AlN which formed solid solution with alumina could reduce heavy metals, while the rest was oxidized by oxygen. In addition, the reduction rates for iron and chromium could be increased with increasing CaF2 from 6.7 to 9.0 wt%. CaF2 could decreased viscosity of molten slag, which favored the ion migration, and then increased the reduction rates. After the reduction, glass ceramics were manufactured from the molten slags. The bending strength, microhardness and alkali resistance of the glass ceramics were up to 77 MPa, 1011 HV and 98.7%, respectively. According to XRD and SEM results, glass ceramics with CaAl2SiO6 crystal phase, crosslinked network structure grains and smaller pores exhibited better bending resistance. In addition, glass ceramics with CaAl2SiO6 crystal phase possessed the highest microhardness and alkali resistance. After this process, hazardous pickling sludge and SAD were totally recycled.
- Published
- 2021
6. CO2 Hydrogenation to Methanol over a Highly Active Cu–Ni/CeO2–Nanotube Catalyst
- Author
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Qingqing Tan, Dongfang Wu, and Zhisheng Shi
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Nanotube ,Materials science ,General Chemical Engineering ,Alloy ,02 engineering and technology ,General Chemistry ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Industrial and Manufacturing Engineering ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,Adsorption ,chemistry ,Chemical engineering ,Yield (chemistry) ,engineering ,Methanol ,0210 nano-technology ,Dispersion (chemistry) ,Bimetallic strip - Abstract
A series of Cu-Ni/CeO2-nanotube catalysts is prepared by an impregnation method for CO2 hydrogenation to CH3OH. Regular CeO2 nanotubes are perfectly formed with a tube diameter of about 30-50 nm and Cu-Ni alloy is well dispersed on CeO2 nanotube without nanotube morphology change. There is a synergistic effect between Ni and Cu, promoting the bimetallic Cu-Ni dispersion, reducibility, CO adsorption and hydrogenation. Additionally, a strong interaction is observed between Cu-Ni alloy and CeO2, and it contributes to partial reduction of Ce4+ to Ce3+ and formation of oxygen vacancies which adsorb and activate CO2. It is shown that both CO2 conversion and CH3OH space-time yield increase at first, reach their maximum values at a Ni/(Cu+Ni) ratio of 2/3, and then decrease with increasing the Ni/(Cu+Ni) ratio. The CeO2-nanotube supported CuNi2 catalyst gives CO2 conversion of 17.8% and CH3OH space-time yield of 18.1 mmol/(gcat∙h) after preliminary optimization. Furthermore, it exhibits an excellent catalytic per...
- Published
- 2018
7. A broadband Pb-chalcogenide/CdS solar cells with tandem quantum-dots embedded in the bulk matrix (QDiM) absorption layers by using chemical bath deposition
- Author
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Zhisheng Shi, Lance L. McDowell, Wanyin Ge, Binbin Weng, Jijun Qiu, and Zhihua Cai
- Subjects
Renewable Energy, Sustainability and the Environment ,Chemistry ,Open-circuit voltage ,Energy conversion efficiency ,Analytical chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,Quantum dot ,law ,Solar cell ,0210 nano-technology ,Absorption (electromagnetic radiation) ,Current density ,Layer (electronics) ,Chemical bath deposition - Abstract
In this paper we have presented a power conversion efficiency (PCE) enhanced Pb-chalcogenide/CdS quantum dots (QDs) solar cells with novel tandem absorption layers synthesized by using chemical bath deposition (CBD) method. The tandem absorption layer is assembled by orderly stacking PbS-QDs layer, PbS-QDiM layer and PbSe-QDiM layer. Compared to single layer PbS-QDs/CdS solar cells, the solar cell with double-tandem layers (PbS-QDiM/QDs) shows the highest short current density ( J sc ) of 47.5 mA/cm 2 due to smoothing of the photo-generated carrier transportation and enhancing the absorption in the visible region 530–800 nm. However, the decreased open circuit voltage (V oc ) of 0.14 eV results in a low power conversion efficiency (PCE) of 2.2%. The triple-tandem absorber (PbSe-QDiM/PbS-QDiM/QDs) enhances the spectra absorption both in the visible (500–800 nm) and near-infrared (1000–1700 nm) regions, resulting in a higher short current density ( J sc ) of 40 mA/cm 2 , while keeping a relatively large open circuit voltage (V oc ) of 0.28 eV. Through an architectural modification, an enhancement of power conversion efficiency (PCE) of 4.2% has been achieved.
- Published
- 2017
8. Nickel sulfide modified TiO 2 nanotubes with highly efficient photocatalytic H 2 evolution activity
- Author
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Xinfa Dong, Zhisheng Shi, and Jiasheng Huang
- Subjects
Materials science ,Photoluminescence ,Nickel sulfide ,Diffuse reflectance infrared fourier transform ,Inorganic chemistry ,Energy Engineering and Power Technology ,Hydrogen production rate ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Fuel Technology ,Chemical engineering ,chemistry ,Transmission electron microscopy ,Electrochemistry ,Photocatalysis ,0210 nano-technology ,Spectroscopy ,Energy (miscellaneous) ,Hydrogen production - Abstract
TiO2 nanotubes (TNTs) with nickel sulfide (NiS) co-catalyst were prepared by a simple solvothermal method and characterized by X-ray diffraction, transmission electron microscope, N2-physisorption, UV–vis diffuse reflectance spectroscopy and photoluminescence spectroscopy. Loading NiS nano-clusters can significantly enhance the photocatalytic H2 evolution performance of TNTs. The optimum NiS loading content was found to be 8 wt% and the corresponding hydrogen production rate is ca. 7486 µmol/h/g, being about 79 times higher than that of pure TNTs. This enhancement of photocatalytic H2 evolution was attributed to the synergistic effect between NiS and TNTs.
- Published
- 2016
9. Theoretical D* Optimization of N+-p Pb1-xSnxSe Long-Wavelength (8 - 11 μm) Photovoltaic Detector at 77 K
- Author
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Zhisheng Shi, Jijun Qiu, Lihua Zhao, Binbin Weng, and Caleb Chang
- Subjects
Long wavelength ,Work (thermodynamics) ,business.industry ,Chemistry ,Diffusion ,Photovoltaic system ,Detector ,Doping ,Optoelectronics ,Quantum efficiency ,business ,Quantum tunnelling - Abstract
In this work, the study of the influences of lifetime, doping concentration and absorption layer thickness to resistant- area product (R0A) and quantum efficiency of Pb1-xSnxSe photovoltaic detector are presented. Three fundamental current mechanisms including diffusion, generation-recombination, and tunneling models are considered. Using optimal doping concentration and absorption layer thickness parameters, the calculated detectivity (D*) of Pb1-xSnxSe photovoltaic detector is over 1012 cm Hz1/2/W.
- Published
- 2014
10. CaF2 surface passivation of lead selenide grown on BaF2
- Author
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Zhisheng Shi, D. Li, S. L. Elizondo, Anurag Gautam, Shaibal Mukherjee, Jiangang Ma, and Gang Bi
- Subjects
Photoluminescence ,Materials science ,Passivation ,business.industry ,Mineralogy ,Carrier lifetime ,Condensed Matter Physics ,Epitaxy ,Atomic and Molecular Physics, and Optics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,Optoelectronics ,Infrared detector ,Electrical and Electronic Engineering ,Thin film ,business ,Layer (electronics) ,Lead selenide - Abstract
A new method of surface passivation of PbSe epitaxial layers by growing a thin epitaxial CaF2 layer is proposed. Improvement in photoluminescence (PL) intensity is observed when the PbSe layer is passivated. The minority carrier lifetime (?), measured by photo-current decay method corroborates PL measurements and shows a consistent, albeit not considerable, improvement in the lifetime of PbSe samples after surface passivation. The positive effect of surface passivation, especially at low heat-sink temperature, offered by a new passivating material is critically important for IV-VI material-based infrared detector and sensor applications.
- Published
- 2011
11. A new in-situ surface treatment during MBE-grown PbSe on CaF2/Si(111) heterostructure
- Author
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Zhisheng Shi, S. L. Elizondo, Shaibal Mukherjee, Gang Bi, D. Li, Jiangang Ma, and F. Zhao
- Subjects
Electron mobility ,Materials science ,Reflection high-energy electron diffraction ,Silicon ,business.industry ,chemistry.chemical_element ,Heterojunction ,Condensed Matter Physics ,Inorganic Chemistry ,Monocrystalline silicon ,Optics ,chemistry ,Electron diffraction ,Materials Chemistry ,Optoelectronics ,Thin film ,business ,Molecular beam epitaxy - Abstract
The continual improvement of IV–VI materials grown by molecular beam epitaxy (MBE) is a key step in the development of IV–VI infrared semiconductor devices on silicon substrates. This study presents a novel surface-treatment method which is carried out during MBE growth of monocrystalline PbSe on Si(1 1 1)-oriented substrates. Details of the experimental procedures are described and supported by reflection high-energy electron diffraction (RHEED) patterns. The effect of the in-situ surface-treatment method is exhibited in the forms of improved electrical and morphological properties of PbSe thin films. Specially, the carrier mobility increases almost three-fold at 77 K and nearly two-fold at 300 K. The density of the growth pits undergoes almost three-fold reduction, whereas the density of the threading dislocations decreases around four-fold.
- Published
- 2009
12. Influence of Oxygen Post-Growth Annealing on Optical and Electrical Properties of PbSe Thin Films
- Author
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D. Li, Shaibal Mukherjee, Gang Bi, Jiangang Ma, F. Zhao, and Zhisheng Shi
- Subjects
Photoluminescence ,Materials science ,Passivation ,Annealing (metallurgy) ,business.industry ,chemistry.chemical_element ,Mineralogy ,Condensed Matter Physics ,Epitaxy ,Oxygen ,Electronic, Optical and Magnetic Materials ,chemistry ,Materials Chemistry ,Optoelectronics ,Electrical and Electronic Engineering ,Dislocation ,Thin film ,business ,Molecular beam epitaxy - Abstract
PbSe thin films grown on (111)-oriented Si substrates by molecular-beam epitaxy were annealed under an oxygen atmosphere with a variety of temperatures and times. The photoluminescence intensity from the sample annealed at 350°C for 2 h was increased by 400-fold with frontside pumping and increased by 40-fold with backside pumping, respectively, in comparison with the as-grown sample. Furthermore, the mobility was increased twofold after annealing. Such large photoluminescence increases and mobility improvements could be attributed to the surface passivation and the dislocation and defect passivation caused by oxygen diffusion and reaction with the PbSe film.
- Published
- 2009
13. Edge-Emitting Lead Salt Mid-Infrared Laser Structure on BaF2 (110) Substrate
- Author
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Shaibal Mukherjee, Gang Bi, D. Li, Zhisheng Shi, Guangzhe Yu, Jiangang Ma, F. Zhao, Dewali Ray, and S. L. Elizondo
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Photoluminescence ,Chemistry ,Barium fluoride ,Analytical chemistry ,chemistry.chemical_element ,Substrate (electronics) ,Heat sink ,Condensed Matter Physics ,Epitaxy ,Laser ,Copper ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry.chemical_compound ,law ,Materials Chemistry ,Electrical and Electronic Engineering ,Molecular beam epitaxy - Abstract
A lead salt mid-infrared laser sample grown by molecular-beam epitaxy (MBE) on a polished BaF2 (110) substrate is studied. For improving the laser performance at higher operating temperature, a method of substrate transfer from a BaF2 substrate to a copper heat sink is developed. The cleaved facet along the {100} plane, which is helpful for the formation of a Fabry-Perot resonant cavity on the laser sample, is observed. Pulsed photoluminescence measurements are conducted on the laser sample step by step during processing in order to trace the effect of each process step.
- Published
- 2009
14. Nature of Growth Pits in Lead Salt Epilayers Grown by Molecular Beam Epitaxy
- Author
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S. L. Elizondo, Shaibal Mukherjee, Gang Bi, D. Li, F. Zhao, Jiangang Ma, and Zhisheng Shi
- Subjects
Chemistry ,Scanning electron microscope ,Crystal growth ,Condensed Matter Physics ,Epitaxy ,Microstructure ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,Crystallography ,Materials Chemistry ,Crystallite ,Electrical and Electronic Engineering ,Lead selenide ,Chemical composition ,Molecular beam epitaxy - Abstract
We present a detailed study on the surface morphologies and chemical composition of growth pits in lead selenide (PbSe) epilayers grown by molecular-beam epitaxy. Various growth pits were investigated by scanning electron microscopy and energy-dispersive x-ray analysis. The vast majority of growth pits within the PbSe epilayers contained either single or multiple PbSe microcrystals with a distinct cuboid shape. Based on the observed structures and morphologies of the PbSe microcrystals, the formation mechanism of the cuboid structures was considered to be (100) preferential crystal growth originating from PbSe polycrystalline seeds.
- Published
- 2008
15. Enhanced photoluminescence from free-standing microstructures fabricated on MBE grown PbSe–PbSrSe MQW structure
- Author
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Zhisheng Shi, Shaibal Mukherjee, J. P. Kar, Sanyog Jain, D. Li, and F. Zhao
- Subjects
Optical fiber ,Fabrication ,Photoluminescence ,Materials science ,business.industry ,chemistry.chemical_element ,Heat sink ,Condensed Matter Physics ,Microstructure ,Copper ,Atomic and Molecular Physics, and Optics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,Semiconductor ,Optics ,chemistry ,law ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Molecular beam epitaxy - Abstract
Fabrication of microrods from multi-quantum well (MQW) PbSe-PbSrSe structure grown in molecular beam epitaxy (MBE) followed by its morphological as well as optical characterizations are described. Pulsed PL intensity is increased by 64 times per unit surface area from a free-standing MQW microrod mounted on copper heat sink compared with the bulk sample. Enhancement in side emission power due to the higher optical confinement effect during pulsed photoluminescence (PL) from MQW semiconductor microtube inserted in hollow quartz optical fiber signifies that these microstructures are robust in nature and crucial contenders for portable mid-infrared optoelectronic devices to be used in the field of industrial trace-gas sensing.
- Published
- 2008
16. Dielectric Charge Screening of Dislocations and Ionized Impurities in PbSe and MCT
- Author
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Shaibal Mukherjee, F. Zhao, Zhisheng Shi, S. L. Elizondo, Jiangang Ma, D. Li, J. P. Kar, and J. Smart
- Subjects
Permittivity ,Condensed matter physics ,Solid-state physics ,Scattering ,Chemistry ,Analytical chemistry ,Dielectric ,Electron ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Impurity ,Electromagnetic shielding ,Materials Chemistry ,Electrical and Electronic Engineering ,Dislocation - Abstract
Recent advancements in IV–VI growth techniques have led to a renewed interest in using Pb1−x Sn x Se for mid infrared (mid-IR) detector fabrication. There is now a greater need for an in-depth theoretical understanding of the potential competitiveness of these material systems with Hg1−x Cd x Te (MCT) especially in regards to material defects and device performance. Herein, we calculate the shielding effects of the dielectric constant by considering the scattering of electrons due to ionized impurities and small charged dislocations. The higher dielectric constant in IV–VI materials, nearly ten times greater than that of MCT, is shown to more effectively screen out the influence of impurities.
- Published
- 2008
17. Strain oriented microstructural change during the fabrication of free-standing PbSe micro-rods
- Author
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Sanyog Jain, Shaibal Mukherjee, F. Zhao, J. P. Kar, Zhisheng Shi, and D. Li
- Subjects
Materials science ,Fabrication ,business.industry ,Barium fluoride ,Condensed Matter Physics ,Epitaxy ,Engraving ,Microstructure ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,Optics ,Semiconductor ,chemistry ,Etching (microfabrication) ,visual_art ,visual_art.visual_art_medium ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Lead selenide - Abstract
In this work, we are reporting fabrication of micro-rods based on epitaxially grown lead selenide (PbSe) on (111) oriented barium fluoride (BaF2). The micro-rods were formed by folding back action of PbSe and their dimension was determined by the initial layer thickness and etching parameters. The micro-rods scattered throughout the surface were measured to have diameters mainly in the range of ∼14–18 μm and lengths ∼40–300 μm. These robust micro-rods can be used for future research on semiconductor microstructures and mid infrared opto-electronic devices.
- Published
- 2007
18. Numerical analysis of CdS/PbSe room temperature mid-infrared heterojunction photovoltaic detectors
- Author
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Wanyin Ge, Zhisheng Shi, Jijun Qiu, and Binbin Weng
- Subjects
Work (thermodynamics) ,Materials science ,business.industry ,Photovoltaic system ,Detector ,Heterojunction ,Cadmium sulfide ,chemistry.chemical_compound ,chemistry ,Electric field ,Optoelectronics ,Crystallite ,business ,Molecular beam epitaxy - Abstract
Numerical analysis of a CdS/PbSe room-temperature heterojunction photovoltaic detector is discussed as to provide guidelines for practical improvement, based on the previous experimental exploration [1]. In our experiment work, the polycrystalline CdS film was prepared in hydro-chemical method on top of the single crystalline PbSe grown by molecular beam epitaxy method. The preliminary results demonstrated a 5.48×108 Jones peak detectivity at λ=4.7μm under zero-bias. However, the influence of some material and device parameters such as carrier concentration, interface recombination velocity remains uncertain. These parameters affect the built-in electric field and the carriers’ transportation properties, and consequently could have detrimental effect on the device performance of the CdS/PbSe detector. In this work, therefore, the numerical analysis is performed based on these parameters. The simulation results suggest that the device performance can be improved at least 4 times by increasing CdS concentration for two orders of magnitudes, and the device performance will degrade severely if the interface recombination speed is over 104 cm/s.
- Published
- 2015
19. MBE growth and characterization of IV–VI semiconductor thin-film structures on (110) BaF2 substrates
- Author
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Xiaoliang Lu, Zhisheng Shi, A. Majumdar, Fanghai Zhao, Roopa Singh, Joel C. Keay, and Dewali Ray
- Subjects
Photoluminescence ,Band gap ,business.industry ,Chemistry ,Substrate (electronics) ,Condensed Matter Physics ,Inorganic Chemistry ,Crystallography ,Laser linewidth ,Semiconductor ,Materials Chemistry ,Optoelectronics ,Thin film ,business ,Quantum well ,Molecular beam epitaxy - Abstract
PbSe thin film and PbSe/PbSrSe multiple quantum well (MQW) structures were successfully grown on (1 1 0) BaF2 substrates by molecular beam epitaxy. The average linewidth of the rocking curve from high-resolution X-ray diffraction measurements of the (2 2 0) reflection for the PbSe thin film was 60 arcsec, which indicates high crystalline quality. The dislocation density estimated from the rocking curve was 1×107 cm−2. Strong photoluminescence (PL) of the MQW structure at room temperature was observed. This PL signal was two times larger than those measured from a duplicate structure grown at the same time on a (1 1 1) BaF2 substrate. The energy bandgap of (1 1 0) PbSe follows the same temperature dependence as [1 0 0]- and [1 1 1]-orientated PbSe.
- Published
- 2005
20. Recent development on the uncooled mid-infrared PbSe detectors with high detectivity
- Author
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Jijun Qiu, Zhisheng Shi, Lihua Zhao, Caleb Chang, Binbin Weng, and Zijian Yuan
- Subjects
Materials science ,Auger effect ,business.industry ,Photoconductivity ,Detector ,Photovoltaic system ,Mid infrared ,Epitaxy ,symbols.namesake ,chemistry.chemical_compound ,chemistry ,symbols ,Optoelectronics ,Mercury cadmium telluride ,Crystallite ,business - Abstract
Polycrystalline lead salt photoconductive (PC) detectors have been widely used for applications in the 1-5μm spectral range because of their low cost, room temperature operation and high detectivity. However, the physical mechanism of such detectors had not been un-ambiguously understood. In order to improve the performance, we proposed a charge separation junction (CSJ) model to analyze and guide our material synthesis process, which has led to PbSe PC detectors with record high detectivity. On the other hand, the performance of photovoltaic (PV) detectors using Pb-salt epitaxial films on Si substrates has been limited by their high defect density even though the ideal performance of the PbSe PV detector was theoretically proven to be higher than the most popular HgCdTe PV detectors at near room temperature, due to its low Auger recombination property. Inspired by the high material quality of self-assembled lead salt microcrystals, we developed a novel method to produce PV detectors using PbSe micro-crystals based on our studies on the PC detector research that showed promising preliminary results.
- Published
- 2013
21. MBE growth of wide band gap Pb1−xSrxSe on Si(111) substrate
- Author
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Zhisheng Shi, G Xu, Patrick J. McCann, and X. M. Fang
- Subjects
Reflection high-energy electron diffraction ,Silicon ,business.industry ,chemistry.chemical_element ,Substrate (electronics) ,Condensed Matter Physics ,Epitaxy ,Inorganic Chemistry ,Crystallography ,chemistry ,Electron diffraction ,Materials Chemistry ,Optoelectronics ,Thin film ,business ,Single crystal ,Molecular beam epitaxy - Abstract
Epitaxial wide band gap Pb 1− x Sr x Se ( x >0.9) layers have been successfully grown by molecular beam epitaxy on Si(1 1 1) and BaF 2 (1 1 1) substrates. Reflection high-energy electron diffraction (RHEED) showed that layers on both substrates were single crystal and oriented to the substrate. X-ray diffraction showed that layers on Si(1 1 1) were high quality as indicated by full-width at half-maximum (FWHM) values of less than 300 arcsec. These results provide a foundation for the eventual fabrications of ultraviolet detector arrays and high power-integrated circuits on silicon substrates.
- Published
- 2000
22. Fabrication of an Electrically Pumped Lead-Chalcogenide Midinfrared Laser on a [110] Oriented PbSnSe Substrate
- Author
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Zhisheng Shi, Dewali Ray, F. Zhao, Shaibal Mukherjee, S. L. Elizondo, Jiangang Ma, Sanyog Jain, and D. Li
- Subjects
Materials science ,Fabrication ,Chalcogenide ,business.industry ,Astrophysics::High Energy Astrophysical Phenomena ,Physics::Optics ,Substrate (electronics) ,Laser ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,law.invention ,Semiconductor laser theory ,Optical pumping ,chemistry.chemical_compound ,Optics ,chemistry ,law ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Lasing threshold ,Molecular beam epitaxy - Abstract
The fabrication of an electrically pumped lead salt- based edge-emitting laser on a polished [110]-oriented PbSnSe substrate is presented. The laser structure was grown by molecular beam epitaxy and consisted of a PbSrSe-PbSe multiple quantum- well active region sandwiched between PbSrSe confinement layers. Pulsed laser emission was observed at lambda = 5.2 mum wavelength up to 158 K with a maximum of 40% duty cycle of current pumping. The repeatability in continuous lasing emission power was also examined.
- Published
- 2008
23. Recent Development of IV-VI Mid-Infrared Photonic Crystal Laser on Silicon
- Author
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Zhisheng Shi, Lin Li, Binbin Weng, and Jijun Qiu
- Subjects
Materials science ,Silicon ,business.industry ,Hybrid silicon laser ,Photonic integrated circuit ,Physics::Optics ,chemistry.chemical_element ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Laser ,law.invention ,Condensed Matter::Materials Science ,Optics ,Semiconductor ,chemistry ,law ,Optoelectronics ,Photonics ,business ,Lasing threshold ,Astrophysics::Galaxy Astrophysics ,Photonic crystal - Abstract
We present our group's recent research progresses of mid-infrared (mid-IR) surface emitting two-dimensional (2D) photonic crystal (PC) lasers via MBE-grown IV-VI group semiconductors on silicon substrates. The device design was based on a 2D micron-level honeycomb structure, in which complete photonic bandgaps will form in mid-IR region. For the initial demonstration, two intensive PC modulated mid-IR light emissions were identified under cryogenic temperature range. After theoretical modification, room temperature surface emitting PC coupled mid-IR lasing was observed recently. With further optimization, room temperature surface emitting continuous wave PC laser is envisioned in the near future.
- Published
- 2012
24. CdS/PbSe heterojunction for high temperature mid-infrared photovoltaic detector applications
- Author
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Zhisheng Shi, Jijun Qiu, Caleb Chang, Binbin Weng, and Lihua Zhao
- Subjects
Materials science ,Physics and Astronomy (miscellaneous) ,Silicon ,business.industry ,chemistry.chemical_element ,Heterojunction ,Photovoltaic effect ,Specific detectivity ,Responsivity ,chemistry ,Optoelectronics ,Thin film ,business ,Molecular beam epitaxy ,Chemical bath deposition - Abstract
n-CdS/p-PbSe heterojunction is investigated. A thin CdS film is deposited by chemical bath deposition on top of epitaxial PbSe film by molecular beam epitaxy on Silicon. Current-voltage measurements demonstrate very good junction characteristics with rectifying ratio of ∼178 and ideality factor of 1.79 at 300 K. Detectors made with such structure exhibit mid-infrared spectral photoresponse at room temperature. The peak responsivity Rλ and specific detectivity D* are 0.055 A/W and 5.482 × 108 cm·Hz1/2/W at λ = 4.7 μm under zero-bias photovoltaic mode. Temperature-dependent photoresponse measurements show abnormal intensity variation below ∼200 K. Possible reasons for this phenomenon are also discussed.
- Published
- 2014
25. Understanding sensitization behavior of lead selenide photoconductive detectors by charge separation model
- Author
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Binbin Weng, Caleb Chang, Zijian Yuan, Zhisheng Shi, Jijun Qiu, and Lihua Zhao
- Subjects
Materials science ,business.industry ,Photoconductivity ,Detector ,Doping ,General Physics and Astronomy ,Electron ,Crystal ,Responsivity ,chemistry.chemical_compound ,chemistry ,Optoelectronics ,Thin film ,business ,Lead selenide - Abstract
We introduce a charge separation model in this work to explain the mechanism of enhanced photoconductivity of polycrystalline lead salt photoconductors. Our results show that this model could clarify the heuristic fabrication processes of such lead salt detectors that were not well understood and often considered mysterious for nearly a century. The improved lifetime and performance of the device, e.g., responsivity, are attributed to the spatial separation of holes and electrons, hence less possibility of carrier recombination. This model shows that in addition to crystal quality the size of crystallites, the depth of outer conversion layer, and doping concentration could all affect detector performance. The simulation results agree well with experimental results and thus offer a very useful tool for further improvement of lead salt detectors. The model was developed with lead salt family of photoconductors in mind, but may well be applicable to a wider class of semiconducting films.
- Published
- 2014
26. Branched double-shelled TiO2 nanotube networks on transparent conducting oxide substrates for dye sensitized solar cells
- Author
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Jijun Qiu, Binbin Weng, Xiaoyan Gan, Xiaomin Li, Zijian Yuan, Xiangdong Gao, Zhisheng Shi, Lin Li, and Yoon-Hwae Hwang
- Subjects
Dye-sensitized solar cell ,Nanotube ,chemistry.chemical_compound ,Materials science ,chemistry ,Tio2 nanotube ,Materials Chemistry ,Oxide ,Branch length ,Nanotechnology ,General Chemistry ,Growth time - Abstract
A novel three-dimensional branched double-shelled TiO2 nanotube network (3DNTNs) structure was constructed on transparent conducting oxide substrates (TCO) by using a ZnO-nanorod array template-assisted method. Various morphological features, such as branch length and population density, could be easily tailored by simply modifying the growth time. The performances of dye-sensitized solar cells (DSCs) fabricated with TiO2 3DNTNs are higher than those assembled with 1-dimensional nanotube arrays. The hollow branches filling in the spaces between the double-shelled stem nanotubes increase the amount of dye-loading, resulting in an enhanced light-harvesting ability.
- Published
- 2012
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