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Abstract The limited sensitivity of photovoltaic-type photodiodes makes it indispensable to use pre-amplifier circuits for effectively extracting electrical signals, especially when detecting dim light. Additionally, the photomultiplication photodiodes with light amplification function suffer from potential damages caused by high power consumption under strong light. In this work, by adopting the synergy strategy of thermal-induced interfacial structural traps and blocking layers, we develop a dual-mode visible-near infrared organic photodiode with bias-switchable photomultiplication and photovoltaic operating modes, exhibiting high specific detectivity (~1012 Jones) and fast response speed (0.05/3.03 ms for photomultiplication-mode; 8.64/11.14 μs for photovoltaic-mode). The device also delivers disparate external quantum efficiency in two optional operating modes, showing potential in simultaneously detecting dim and strong light ranging from ~10−9 to 10−1 W cm−2. The general strategy and working mechanism are validated in different organic layers. This work offers an attractive option to develop bias-switchable multi-mode organic photodetectors for various application scenarios.

Abstract Black phosphorus quantum dots (BPQDs) are synthesized and combined with graphene sheet. The fabricated BPQDs/graphene devices are capable of detecting visible and near infrared radiation. The adsorption effect of BPQDs in graphene is clarified by the relationship of the photocurrent and the shift of the Dirac point with different substrate. The Dirac point moves toward a neutral point under illumination with both SiO2/Si and Si3N4/Si substrates, indicating an anti-doped feature of photo-excitation. To our knowledge, this provides the first observation of photoresist induced photocurrent in such systems. Without the influence of the photoresist the device can respond to infrared light up to 980 nm wavelength in vacuum in a cryostat, in which the photocurrent is positive and photoconduction effect is believed to dominate the photocurrent. Finally, the adsorption effect is modeled using a first-principle method to give a picture of charge transfer and orbital contribution in the interaction of phosphorus atoms and single-layer graphene. Graphical Abstract

The NH3 sensor is of great significance in preventing NH3 leakage and ensuring life safety. In this work, the Pd-decorated ZnO hexagonal microdiscs are synthesized using hydrothermal and annealing processes, and the gas sensor is fabricated based on Pd-decorated ZnO hexagonal microdiscs. The gas-sensing test results show that the Pd-ZnO gas sensor has a good response to NH3 gas. Specifically, it has a good linear response within 0.5–50 ppm NH3 at the optimal operating temperature of 230 °C. In addition, the Pd-ZnO gas sensor exhibits good repeatability, short response time (23.2 s) and good humidity resistance (10–90% relative humidity). This work provides a useful reference for developing an NH3 sensor.

As drone technology grows in popularity, its application to automate aspects of society is increasing at a similar rate, where drones are now being trialled for delivering payloads over short distances. In order to progress the technology, 3D composite printing is being used to develop complicated parts for improved aerodynamic design that can be produced efficiently, where the resultant composite part has high specific strength and rigidity. This article reports 3D printing of high specific strength, high-temperature Polyamide 6 (Onyx), continuous glass-fibre reinforced Onyx, and carbon-fibre reinforced Onyx composites and characterising their mechanical and fracture behaviour. The Onyx + CF composites displayed up to 1243 % and 1344 % improvement in Young's modulus and tensile strength over neat Onyx samples. The flexural strength of Onyx + CF samples was up to 316.6 % higher than the flexural strength of the neat Onyx sample. SEM micrographs showed a strong bond between the hydration products and the carbon fibres, increasing their tensile and flexural strengths by preventing micro-crack propagation through fibre pull-out and breaking. The statistical analysis was conducted to ensure the validity of the results for the population and establish stress-strain relations, along with estimating errors. In addition, the carbon-fibre-reinforced Onyx composite was compared with commercially used alternatives for producing drone components. Finally, a finite element model was developed using a numerical homogenisation approach and validated to predict the tensile and flexural behaviour of Onyx and carbon-fibre reinforced Onyx samples. This study provides a direction for the next generation of drone manufacturers.

Abstract The recent emergence of non‐fullerene acceptors (NFAs) has energized the field of organic photodiodes (OPDs) and made major breakthroughs in their critical photoelectric characteristics. Yet, stabilizing inverted NF‐OPDs remains challenging because of the intrinsic degradation induced by improper interfaces. Herein, a tin ion‐chelated polyethyleneimine ethoxylated (denoted as PEIE‐Sn) is proposed as a generic cathode interfacial layer (CIL) of NF‐OPDs. The chelation between tin ions and nitrogen/oxygen atoms in PEIE‐Sn contributes to the interface compatibility with efficient NFAs. The PEIE‐Sn can effectively endow the devices with optimized cascade alignment and reduced interface defects. Consequently, the PEIE‐Sn‐OPD exhibits properties of anti‐environmental interference, suppressed dark current, and accelerated interfacial electron extraction and transmission. As a result, the unencapsulated PEIE‐Sn‐OPD delivers high specific detection and fast response speed and shows only slight attenuation in photoelectric performance after exposure to air, light, and heat. Its superior performance outperforms the incumbent typical counterparts (ZnO, SnO2, and PEIE as the CILs) from metrics of both stability and photoelectric characteristics. This finding suggests a promising strategy for stabilizing NF‐OPDs by designing appropriate interface layers.

Van der Waals heterostructures of black phosphorous(BP) and Molybdenum Disulfide(MoS2) is designed and evaluated for photodetection application from visible to mid-infrared wavelength up to 4.5 μm. The device possesses a low dark current less than 0.1 μA for short wavelength light. For visible and near infrared radiation, the contribution of heat and photo energy to current enhancement is analyzed. Dark current drift by joule heat and laser heat absorbed is observed in short waveband. The difference in response speed is believed to be a result of the competition of BP and MoS2 photocurrent. Gate tunable response time and on-off ratio makes the device versatile in potential application. For mid infrared radiation, BP-MoS2 heterojunction with a dedicated thickness tailoring of MoS2 exhibits similar negative response as an intrinsic BP. The normalized detectivity is ${D}^*$ of $2.02 \times {10}^8\ Jones$ for the 4.5 μm mid-infrared radiation. Elaborate reduction of the noise is conducted to get the time resolvable photo-response. A low bias is necessary for a time resolved photocurrent, reducing the flicker noise to an acceptable level.

The piezoelectricity of PVDF composites is mainly determined by the crystalline phases and spontaneous polarization. Here, the authors propose a Ti3C2Tx anchoring method to modulate the molecular interactions and conformation of polymer matrix.

Abstract Piezoelectric nanocomposites with oxide fillers in a polymer matrix combine the merit of high piezoelectric response of the oxides and flexibility as well as biocompatibility of the polymers. Understanding the role of the choice of materials and the filler‐matrix architecture is critical to achieving desired functionality of a composite towards applications in flexible electronics and energy harvest devices. Herein, a high‐throughput phase‐field simulation is conducted to systematically reveal the influence of morphology and spatial orientation of an oxide filler on the piezoelectric, mechanical, and dielectric properties of the piezoelectric nanocomposites. It is discovered that with a constant filler volume fraction, a composite composed of vertical pillars exhibits superior piezoelectric response and electromechanical coupling coefficient as compared to the other geometric configurations. An analytical regression is established from a linear regression‐based machine learning model, which can be employed to predict the performance of nanocomposites filled with oxides with a given set of piezoelectric coefficient, dielectric permittivity, and stiffness. This work not only sheds light on the fundamental mechanism of piezoelectric nanocomposites, but also offers a promising material design strategy for developing high‐performance polymer/inorganic oxide composite‐based wearable electronics.

Abstract Preparing the thermal-sensitive thin films with high temperature coefficient of resistance (TCR) and low resistivity by a highly compatible process is favorable for increasing the sensitivity of microbolometers with small pixels. Here, we report an effective and process-compatible approach for preparing V1-x-yTixRuyO2 thermal-sensitive thin films with monoclinic structure, high TCR, and low resistivity through a reactive sputtering process followed by annealing in oxygen atmosphere at 400 °C. X-ray photoelectron spectroscopy demonstrates that Ti4+ and Ru4+ ions are combined into VO2. X-ray diffraction, Raman spectroscopy, and transmission electron microscopy reveal that V1-x-yTixRuyO2 thin films have a monoclinic lattice structure as undoped VO2. But V1-x-yTixRuyO2 thin films exhibit no-SMT feature from room temperature (RT) to 106 °C due to the pinning effect of high-concentration Ti in monoclinic lattice. Moreover, RT resistivity of the V0.8163Ti0.165Ru0.0187O2 thin film is only one-eighth of undoped VO2 thin film, and its TCR is as high as 3.47%/°C.

Abstract In this study, by inserting a buffer layer of TiO x between the SiO x :Ag layer and the bottom electrode, we have developed a memristor device with a simple structure of Ag/SiO x :Ag/TiO x /p++-Si by a physical vapor deposition process, in which the filament growth and rupture can be efficiently controlled during analog switching. The synaptic characteristics of the memristor device with a wide range of resistance change for weight modulation by implementing positive or negative pulse trains have been investigated extensively. Several learning and memory functions have been achieved simultaneously, including potentiation/depression, paired-pulse-facilitation (PPF), short-term plasticity (STP), and STP-to-LTP (long-term plasticity) transition controlled by repeating pulses more than a rehearsal operation, and spike-time-dependent-plasticity (STDP) as well. Based on the analysis of logarithmic I-V characteristics, it has been found that the controlled evolution/dissolution of conductive Ag-filaments across the dielectric layers can improve the performance of the testing memristor device.

Currently, wind energy, a reliable, affordable, and clean energy source, contributes to 16% of Europe’s electricity. A typical modern wind turbine design lifespan is 20 years. In European Union countries, the number of wind turbines reaching 20 years or older will become significant beyond 2025. This research study presents a methodology aiming to upgrade rotor blades for existing wind turbines to extend the turbine life. This methodology employs blade element momentum theory, finite element analysis, genetic algorithm, and direct screen methods to optimise the blade external geometry and structural design, with the main objective to increase the blade power capture efficiency and enhance its structural performance. Meanwhile, the compatibility between the blade and the existing rotor of the wind turbine is considered during the optimisation. By applying this methodology to a 225 kW wind turbine, an optimal blade, which is compatible with the turbine hub, is proposed with the assistance of physical testing data. The optimised blade, which benefits from high-performance carbon-fibre composite material and layup optimisation, has a reduced tip deflection and self-weight of 48% and 31%, respectively, resulting in a significant reduction in resources, while improving its structural performance. In addition, for the optimised blade, there is an improvement in the power production of approximately 10.5% at a wind speed of 11 m/s, which results in an increase of over 4.2% in average annual power production compared to the existing turbine, without changing the blade length. Furthermore, an advanced aero-elastic-based simulation is conducted to ensure the changes made to the blade can guarantee an operation life of at least 20 years, which is equivalent to that of the reference blade.

Processing layer-dependent direct band gap and good absorption coefficient especially in the mid-infrared band, black phosphorous is believed to make a contribution superior to that of graphene in broadband photodetectors. The narrow band gap of 0.3 eV for bulk black phosphorous helps to absorb infrared radiation while a relatively large dark current under zero gate voltage is inevitable. Few layer black phosphorous sheets with asymmetrical thickness sealed in an insulator for protection is designed and explored for photosensitive mechanism in this work. Saturable absorption dominates the light harvesting process in visible light detection and thus limits maximum photocurrent to 3.3 and 1.4 μA for 520 and 650 nm lasers with a dark current of 0.7 μA. While in near-infrared wavelength, a responsivity of 0.12 A/W is inducted for 808 nm free of adsorption saturation even if the incident power is increased to 200 mW/cm2. Discrimination for the origin of the photo-response in short wavelength is conducted and the abnormal negative and nearly constant photocurrent in mid-infrared, irrelevant to inhomogeneous thickness, reveals the photothermal effect in a black phosphorous sheet. This work unravels various photoelectric features in black phosphorous and paves the way to designing more outstanding broadband photodetectors based on black phosphorous.

Recently, photonic synapses that can directly respond to light signals have attracted much attention due to their huge application potential in neuromorphic chips and artificial vision systems. However, the implementation of an artificial visual system based on a synapse remains a considerable challenge due to the limitation that most current photonic synapses fail to recognize color. Here, a photonic synapse with color recognition capability is proposed and demonstrated. Through the light‐induced adjustment of dangling bond defects inside the amorphous silicon (a‐Si) film, the device exhibits switchable volatile and nonvolatile photoconductivity (PC) behaviors at the wavelengths of 635 and 450 nm, respectively. Based on the dual PC, the photonic synapse enables dual synaptic plasticity depending on the stimulation light, allowing not only various synaptic functions, but also learning experiences, associative learning behaviors, and recognition of the red and blue colors. Moreover, the dual synaptic plasticity of the photonic synapse could be modulated via a voltage in the range below ≈1 V to realize the stable detection and precise extraction of the grayscale and color signals. With its simple structure and compatibility with existing Si‐complementary metal oxide semiconductor (CMOS) technology, this photonic synapse shows potential for application in neuromorphic computing and advanced robot vision systems.

In this paper, a double-band visible-infrared photodetector absorber is proposed, which consists of a modified microbolometer and a metallic reflective layer which has a deep well. The simulated results show that the absorber proposed has high absorption peaks both at visible band (400–800 nm) and infrared band (8–12 μm), and the absorptivity at infrared band is more than 85% while the absorption rate at visible band exceeds 70%. By analyzing the simulation results, the absorption mechanism is discussed. The designed absorber not only has high absorption rate, but also realizes visible-infrared double band coaxial absorption with single pixel integration, hence it is favorable for various applications, such as night and day vision coaxial detecting, double band fusion detecting, and optical filter and bio-chemical sensor.

Abstract Silicon is widely used in semiconductor industry but has poor performance in near-infrared photoelectronic devices because of its high reflectance and band gap limit. In this study, two-step process, deep reactive ion etching (DRIE) method combined with plasma immersion ion implantation (PIII), are used to fabricate microstructured black silicon on the surface of C-Si. These improved surfaces doped with sulfur elements realize a narrower band gap and an enhancement of light absorptance, especially in the near-infrared range (800 to 2000 nm). Meanwhile, the maximum light absorptance increases significantly up to 83%. A Si-PIN photoelectronic detector with microstructured black silicon at the back surface exhibits remarkable device performance, leading to a responsivity of 0.53 A/W at 1060 nm. This novel microstructured black silicon, combining narrow band gap characteristic, could have a potential application in near-infrared photoelectronic detection.

In this paper, a double-band tunable perfect THz metamaterial absorber (MA) is proposed, which includes a ring-shaped dielectric layer and a Dirac material layer. The simulated results indicate that the absorber has two peaks of high absorptivity at 2.02 THz and 2.49 THz, and the corresponding absorption rate is more than 99%. The Fermi energy of the BDSs could be changed to regulate the absorption peak of MA, with the change of the Fermi energy level from 55 meV to 85 meV, a dynamic adjustment of absorption rate from 90% to 99% could be effectively controlled. The absorption property of the MA unit cell is polarization independent for TE and TM polarizations because of its central symmetry. The absorber proposed not only has high absorption rate, but also has tunable absorption peak, hence it is appropriate for a series of direction of applications, such as medical sensor, optical filter and THz detecting. Keywords: BDSs, Terahertz, Tunable, Perfect absorber

Abstract Antenna-coupled micro-bridge structure is proven to be a good solution to extend infrared micro-bolometer technology for THz application. Spiral-type antennas are proposed in 25 μm × 25 μm micro-bridge structure with a single separate linear antenna, two separate linear antennas, or two connected linear antennas on the bridge legs, in addition to traditional spiral-type antenna on the support layer. The effects of structural parameters of each antenna on THz absorption of micro-bridge structure are discussed for optimized absorption of 2.52 THz wave radiated by far infrared CO2 lasers. The design of spiral-type antenna with two separate linear antennas for wide absorption peak and spiral-type antenna with two connected linear antennas for relatively stable absorption are good candidates for high absorption at low absorption frequency with a rotation angle of 360*n (n = 1.6). Spiral-type antenna with extended legs also provides a highly integrated micro-bridge structure with fast response and a highly compatible, process-simplified way to realize the structure. This research demonstrates the design of several spiral-type antenna-coupled micro-bridge structures and provides preferred schemes for potential device applications in room temperature sensing and real-time imaging.

In this paper, we propose a spectrally and spatially tunable terahertz metasurface lens based on the surface plasmons of graphene ribbons. By tuning the graphene Fermi energy, the optical property of graphene surface plasmons can be dynamically modulated, leading to tailored abrupt phase shifts of the reflected light. We demonstrate a resulting large spectral tuning range from 4 to 6 THz for the proposed metasurface lens with a spatially adjustable focal point in tens of micrometers. The influence of electron relaxation time of graphene and thickness of ion-gel on the performance of the metasurface lens is also discussed. Such a terahertz metasurface lens with a large spectral and spatial tunability is expected to show the great potentials in realizing active terahertz elements.

In this paper, a triple-band terahertz metamaterial absorber (MA) based on buck Dirac semimetals (BDSs) is proposed, which consists of a windmill-shaped element in a square ring layer, a dielectric layer, and a BDSs layer. The MA unit cell is investigated at normal and oblique incidence angle for both transverse electric (TE) and transverse magnetic (TM) polarizations. The simulation results show that the MA has three high absorption peaks at 0.80 THz, 1.72 THz, and 3.38 THz. The corresponding peak absorbance are 99.43%, 99.92% and 99.58%, respectively. Moreover, the absorption peaks of MA can be tuned by adjusting the Fermi energy of the BDSs. And the density of electric field, the magnetic field, and surface current distributions of the MA are given to reveal the absorption mechanism. According to the simulation results, the designed MA not only has high absorbance, but also insensitive to polarizations. Hence it is favorable for various applications, such as terahertz detecting, radar stealth and bio-chemical sensor. Keywords: BDSs, Terahertz, Perfect absorber, Polarization-independent

The functional groups of organic gas-sensing materials play a crucial role in adsorbing specific gas molecules, which is significant to the sensing performances of gas sensor. In this work, amido-graphene oxide (GO-NH2) loaded poly(ethyleneimine) (PEI) composite thin film (PEI/GO-NH2) with abundant amino functional groups -NH2 was successfully prepared on quartz crystal microbalance (QCM) by a combined spraying and drop coating method for acetone detection at room temperature (25°C). The morphological, spectrographic and acetone-sensing properties of composite film were investigated. The results demonstrated that a wrinkled surface morphology was formed and the ratio of nucleophilic -NH2 was increased for PEI/GO-NH2 composite film. Meanwhile, the composite film sensor possessed excellent acetone-sensing performances, and its sensitivity was about 4.2 times higher than that of pure PEI one owing to the increased -NH2 groups. This study reveals the important role of absorbing favorable functional groups and provides a novel method for the rational design and construction of acetone-sensing materials.

Quarter-wavelength cavity, as a classical structure for preventing wave reflection, presents an effective way to enhance the interaction between light and material of ultrathin thickness. In this paper, we propose a method to control the bandwidth of graphene’s enhanced absorption in quarter-wavelength cavity. By varying the spacing distance between graphene and a metallic reflecting plane, which equals to an odd number of quarter-wavelengths, fundamental and higher order cavity modes are excited, whose fields couple to graphene with different spectral bandwidths, leading to bandwidth-controllable absorption in graphene. Absorption efficiencies of 9% and 40% are measured for graphene monolayer at 15° and 85° incident angles, respectively. Its absorption bandwidth varies between 52% and 10% of the central wavelength when the spacing distance between graphene and metallic reflecting plane increases from a quarter wavelength to seven quarter wavelengths. Our findings pave a way in engineering graphene for strong absorption with a controllable bandwidth, which has potential applications in tailoring spectral response of graphene-based optoelectronic devices.

As the world shifts to using renewable sources of energy, wind energy has been established as one of the leading forms of renewable energy. As the requirement for wind energy increases, so too does the size of the turbines themselves, where the latest turbines are 10 MW with a turbine diameter in excess of 190 m. The design and manufacture of the blades for these turbines will be critical if they are to last for the design life, where the accuracy of the numerical models used in the design process is paramount. Therefore, in this paper, three independent numerical models have been created using three available finite element method packages—ABAQUS, ANSYS, and CalculiX—and the results were compiled. Following this, the accuracy of the models has been evaluated and validated against the results from an experimental testing campaign. In order to complete the study, a 13 m full-scale wind turbine blade has been used, which has been subjected to static testing in both the edgewise and flapwise directions. The results from this testing campaign, along with the blade mass and natural frequencies, have been compared to the results from the independent numerical models. The differences in the models, along with other sources of error, have been discussed, which includes recommendations on the development of accurate numerical models.

In this paper an original numerical model, based on the standard Berg model, was used to simulate the growth mechanism of NiCrxOy deposited with changing oxygen flow during reactive sputter deposition. The effect of oxygen flow rate on the discharge voltage, deposition rate and the material elementary composition were investigated. The ratio of Ni and Cr content in the film was measured using energy-dispersive X-ray spectroscopy (EDX). EDX detected a decrease in the Cr concentration with the increasing of oxygen flow rate due to the preferential oxidation of Cr to Cr2O3. Results show a reasonable agreement between numerical and experimental data.DOI: http://dx.doi.org/10.5755/j01.ms.22.2.8563

Reactive sputter processes frequently exhibit stability problems. The cause of this is that these processes normally exhibit hysteresis effects in the processing curves. Eliminating or decreasing the hysteresis would significantly simplify the use of reactive sputtering processes. In this work, we present reactive sputtering deposition modeling of vanadium oxide with a revolutionary substrate, aiming to study the influence of it on hysteresis effect. Based on this modeling, the fractions of V, V2O3, VO2, V2O5 at the target surface and target voltage have been investigated as a function of reactive gas flow during the reactive sputtering. The substrate area was replaced by a new parameter of effective area of substrate As which was calculated as a sum of contributions from the substrate area at each cell of time. From the modeling results, it is suggested that the effective area of the substrate was reduced for reactive sputtering with revolutionary substrate, thus the hysteresis width would be decreased. This has been experimentally verified by reactive sputtering deposition of VOx. Besides, the fundamental explanation to this behavior as well as the experimental verification is presented.DOI: http://dx.doi.org/10.5755/j01.ms.22.1.7569

Tunable complementary split ring resonators (CSRRs) based on monolayer graphene are presented in terahertz regime. By applying different gate voltage, the Fermi level and optical conductivity of monolayer graphene pattern can be changed. Here, we employ a numerical simulation to study the interaction of light with graphene CSRRs. The results indicate that the extinction in transmission becomes stronger, and the resonance frequency presents blue shift with higher Fermi level of the graphene pattern. Three pronounced resonant peaks appear which can be modulated dynamically in the range of 1-2THz and 3-7THz, and realizing dynamic broadband terahertz modulation, the modulation depth exceeds 85% at all three resonant peaks, the highest modulation depth reaches 98.8% at 7.47THz.

Electrical driving is one of frequently-used stimuli for the semiconductor-metal transition (SMT) of VO2. But the driving mechanism is still under debate. We investigated the DC electrically-driven SMT features of polycrystalline VO2 thin films deposited on two kinds of substrates (quartz and silicon) with obviously-different thermal conductivity and the influence of cooling by a thermo electric cooler (TEC) on the SMT of VO2. Interestingly, the SMT doesn’t happen at a high voltage at very start, but at a relatively low one. Moreover, the SMT of VO2 thin films on silicon substrate is completely restrained by cooling through a TEC although the electric field strength across VO2 reaches 1.1×107 V/m. Our findings reveal that the Joule-heating effect plays an important role in the DC electrically-driven SMT of VO2.

A linear hydrogen-bond acidic (HBA) linear functionalized polymer (PLF), was deposited onto a bare surface acoustic wave (SAW) device to fabricate a chemical sensor. Real-time responses of the sensor to a series of compounds including sarin (GB), dimethyl methylphosphonate (DMMP), mustard gas (HD), chloroethyl ethyl sulphide (2-CEES), 1,5-dichloropentane (DCP) and some organic solvents were studied. The results show that the sensor is highly sensitive to GB and DMMP, and has low sensitivity to HD and DCP, as expected. However, the sensor possesses an unexpected high sensitivity toward 2-CEES. This good sensing performance can’t be solely or mainly attributed to the dipole-dipole interaction since the sensor is not sensitive to some high polarity solvents. We believe the lone pair electrons around the sulphur atom of 2-CEES provide an electron-rich site, which facilitates the formation of hydrogen bonding between PLF and 2-CEES. On the contrary, the electron cloud on the sulphur atom of the HD molecule is offset or depleted by its two neighbouring strong electron-withdrawing groups, hence, hydrogen bonding can hardly be formed.

The electrical, optical and mechanical properties of compound oxides film depend strongly on the composition of the film, especially for vanadium oxide thin films, since the vanadium-oxygen phase diagram includes mixed valence oxides with two or more oxidation states. Therefore, it is interesting to predict the film stoichiometry in VOx films. However, it has not, to any great extent yet, been possible to predict the composition of vanadium oxides films. In this article, we present a model that enables us to predict film composition of vanadium oxides prepared by reactive sputtering. Based on this model, the fraction ratio of V, V2O3, VO2 and V2O5 in the substrate surface as a function of oxygen flow is investigated. It is concluded that the presented theoretical model for the involved reactions and composition of VOx thin film during reactive sputtering process is in qualitative agreement with the XPS results from experiment and can be used to find optimum processing conditions for deposition of films of a desired composition.DOI: http://dx.doi.org/10.5755/j01.ms.21.2.6910

A thin-film transistor (TFT) having an organic–inorganic hybrid thin film combines the advantage of TFT sensors and the enhanced sensing performance of hybrid materials. In this work, poly(3-hexylthiophene) (P3HT)-zinc oxide (ZnO) nanoparticles’ hybrid thin film was fabricated by a spraying process as the active layer of TFT for the employment of a room temperature operated formaldehyde (HCHO) gas sensor. The effects of ZnO nanoparticles on morphological and compositional features, electronic and HCHO-sensing properties of P3HT-ZnO thin film were systematically investigated. The results showed that P3HT-ZnO hybrid thin film sensor exhibited considerable improvement of sensing response (more than two times) and reversibility compared to the pristine P3HT film sensor. An accumulation p-n heterojunction mechanism model was developed to understand the mechanism of enhanced sensing properties by incorporation of ZnO nanoparticles. X-ray photoelectron spectroscope (XPS) and atomic force microscopy (AFM) characterizations were used to investigate the stability of the sensor in-depth, which reveals the performance deterioration was due to the changes of element composition and the chemical state of hybrid thin film surface induced by light and oxygen. Our study demonstrated that P3HT-ZnO hybrid thin film TFT sensor is beneficial in the advancement of novel room temperature HCHO sensing technology.

As an emerging 2D material, graphene’s several unique properties, such as high electron mobility, zero-bandgap and low density of states, present new opportunities for light detections. Here, we report on photovoltage responses of graphene-Au heterojunctions, which are made of monolayer graphene sheets atop Au electrodes designed as finger-shape and rectangle-shape, respectively. Besides confirming the critical role of space charge regions located at the graphene-Au boundary, photovoltage responses are measured in the visible to infrared spectral region with a cut-off wavelength at about 980 nm, which is likely imposed by the Pauli blocking of interband transition in the contact-doped graphene. The photoresponsivity is shown to decrease with increasing wavelength. A band diagram of the graphene-Au heterojunction is proposed to understand the photoresponse mechanism.

We present a p-n-p monolayer graphene photodetector doped with titanium dioxide nanotubes for detecting light from visible to near-infrared (405 to 1310 nm) region. The built-in electric field separates the photo-induced electrons and holes to generate photocurrent without bias voltage, which allows the device to have meager power consumption. Moreover, the detector is very sensitive to the illumination area, and we analyze the reason using the energy band theory. The response time of the detector is about 30 ms. The horizontal p-n-p device is a suitable candidate in zero-bias optoelectronic applications.

Infrared photodetectors are gaining remarkable interest due to their widespread civil and military applications. Low-dimensional materials such as quantum dots, nanowires, and two-dimensional nanolayers are extensively employed for detecting ultraviolet to infrared lights. Moreover, in conjunction with plasmonic nanostructures and plasmonic waveguides, they exhibit appealing performance for practical applications, including sub-wavelength photon confinement, high response time, and functionalities. In this review, we have discussed recent advances and challenges in the prospective infrared photodetectors fabricated by low-dimensional nanostructured materials. In general, this review systematically summarizes the state-of-the-art device architectures, major developments, and future trends in infrared photodetection.

A facile approach of body modification on substrate is introduced to enhance the light extraction for organic devices. The lateral metal reflective film (LMRF) was coated on side of substrate and microlens array (MLA) was fabricated on forward surface of substrate. The two methods of improving light output are simulated and optimized to form body modification. The metal thin film was evaporated on the side of reversal trapezoid shape substrate to form LMRF layer and the MLA with semicircle shape was fabricated on the substrate using normal photolithography process. The external quantum efficiency of fabricated organic device with body modification is ~1.8 times higher than the device with normal substrate.