Search

In this work, metal-insulator-semiconductor (MIS) capacitor structure was used to investigate the dielectric charging and discharging in the capacitive radio frequency microelectromechanical switches. The insulator in MIS structure is silicon nitride films (SiN), which were deposited by either low pressure chemical vapor deposition (LPCVD) or plasma enhanced chemical vapor deposition (PECVD) processes. Phosphorus or boron ions were implanted into dielectric layer in order to introduce impurity energy levels into the band gap of SiN. The relaxation processes of the injected charges in SiN were changed due to the ion implantation, which led to the change in relaxation time of the trapped charges. In our experiments, the space charges were introduced by stressing the sample electrically with dc biasing. The effects of implantation process on charge accumulation and dissipation in the dielectric are studied by capacitance-voltage (C-V) measurement qualitatively and quantitatively. The experimental results show that the charging and discharging behavior of the ion implanted silicon nitride films deposited by LPCVD is quite different from the one deposited by PECVD. The charge accumulation in the dielectric film can be reduced by ion implantation with proper dielectric deposition method. [ABSTRACT FROM AUTHOR]

Abstract: The current paper presents a theoretical analysis of Ni-63 nuclear micro-battery based on a wide-band gap semiconductor GaN thin-film covered with thin Ni/Au films to form Schottky barrier for carrier separation. The total energy deposition in GaN was calculated using Monte Carlo methods by taking into account the full beta spectral energy, which provided an optimal design on Schottky barrier width. The calculated results show that an 8μm thick Schottky barrier can collect about 95% of the incident beta particle energy. Considering the actual limitations of current GaN growth technique, a Fe-doped compensation technique by MOCVD method can be used to realize the n-type GaN with a carrier concentration of 1×1015 cm−3, by which a GaN based Schottky betavoltaic micro-battery can achieve an energy conversion efficiency of 2.25% based on the theoretical calculations of semiconductor device physics. [Copyright &y& Elsevier]

Abstract: Transparent conducting oxides CdIn2O4 thin films were prepared by radio-frequency reactive sputtering from a Cd–In alloy target in Ar+O2 atmosphere. By transmission spectrum and Hall measurement for different samples prepared at different substrate temperatures, it could be found that the carrier concentration would increase with the decrease of substrate temperature, but absorption edge showed an abrupt variation from a blue shift to a red shift. Theoretically, the paper formulated the effect of high-density point defects on band structures; it embodied the formation of band tailing, Burstein-Moss shift and band-gap narrowing. The density of holes will influence the magnitude of optical band gap and transmittance of light. Since extrapolation method does not fit degenerate semiconductor materials, a more accurate method of obtaining optical band gap is curve fitting. In addition, ionized impurities scattering is the main damping mechanism of the free electrons in CdIn2O4 films, the density of ionized impurities induced by altering substrate temperature will affect the carriers mobility. [Copyright &y& Elsevier]

Clean energy is a major trend. The importance of photovoltaic power generation is also growing. Photovoltaic power generation is mainly affected by the weather. It is full of uncertainties. Previous work has relied chiefly on historical photovoltaics data for time series forecasts. However, unforeseen weather conditions can sometimes skew. Consequently, a spatial‐temporal‐meteorological‐long short‐term memory prediction model (STM‐LSTM) is proposed to compensate for the shortage of photovoltaic prediction models for uncertainties. This model can simultaneously process satellite image data, historical meteorological data, and historical power generation data. In this way, historical patterns and meteorological change information are extracted to improve the accuracy of photovoltaic prediction. STM‐LSTM processes raw satellite data to obtain cloud image data. It can extract cloud motion information using the dense optical flow method. First, the cloud images are processed to extract cloud position information. By adaptive attentive learning of images in different bands, a better representation for subsequent tasks can be obtained. Second, it is important to process historical meteorological data to learn meteorological change patterns. Last but not least, the historical photovoltaic power generation sequences are combined to obtain the final photovoltaic prediction results. After a series of experimental validation, the performance of the proposed STM‐LSTM model has a good improvement compared with the baseline model. [ABSTRACT FROM AUTHOR]

Si OCN ceramics are formed by the thermal decomposition of a polyvinylsilazane precursor in the presence of a dicumyl peroxide ( DP) thermal initiator with different concentrations. The Si OCN ceramics pyrolyzed at 1000°C with different concentrations of DP are characterized with X-ray diffraction, transmission electron microscope, electron paramagnetic resonance, and UV-visible spectroscopy. We find that the structure and optical band gap of the Si OCN ceramics can be changed by altering the concentration of DP. There is a critical concentration, at which the structural and optical behavior varied in different ways as a function of the concentration of DP. The detailed mechanism is discussed. [ABSTRACT FROM AUTHOR]

We report the fabrication of sandwich-type metal/TiO 2 nanotube (TNT) array/metal structures as well as their betavoltaic effects under build-in voltage through contact potential difference. The sandwiched structure is integrated by immobilized TNT arrays on Ti foil with radioisotope 63 Ni planar source on Ni substrate (Ni– 63 Ni/TNT array/Ti). Under irradiation of the 63 Ni source with activity of 8 mCi, the structure (TNT diameter ∼ 130 nm, length ∼ 11 μm) presents optimum energy conversion efficiency of 7.30% with open-circuit voltage of 1.54 V and short-circuit current of 12.43 nA. The TNT arrays exhibit a highly potential for developing betavoltaic batteries due to its wide band gap and nanotube array configuration. The TNT-betavoltaic concept offers a facile solution for micro/nano electronics with high efficiency and long life-time instead of conventional planar junction-type batteries. [ABSTRACT FROM AUTHOR]

We report a facile route to synthesize Si CO nanospheres using Pluronic F127/polyvinylsilazane ( PVSZ) mixed micelles as a template, in which PVSZ selectively swells with the PEO core of the F127 micelles. The thermal degradation of the F127/ PVSZ mixed micelles leads to the formation of Si CO nanospheres. The size of the resultant Si CO nanospheres can be tuned in the range from 25 nm to 75 nm by controlling annealing time at 70°C. [ABSTRACT FROM AUTHOR]

The polyyttriocarbosilane (PYCS) with various quantities of yttrium was obtained by reacting yttrium acetylacetonate (Y(AcAc)) with polycarbosilane (PCS). The molecular weight, softening point, and Si-H bond content of the resulting PYCS are controlled by the Y(AcAc):PCS weight ratio, reaction temperature and reaction time. The main chain of the PYCS is made up of alternating carbon and silicon atoms with small amount of Si-O-Y presented in the main chain and Si-H groups at the side chain. The pyrolysis process of PYCS was investigated by TG and XRD. The results reveal that the polymer-to-ceramic transition of the PYCS occurs in three steps. The final ceramics obtained at 1,800 °C contain a large number of β-SiC crystallites and a small amount of α-SiC crystallites. [ABSTRACT FROM AUTHOR]

This paper reports a 3-dimentional (3D) pressure sensor based on surface acoustic wave (SAW) resonators. The SAW resonators were designed and fabricated on 128°Y-X LiNbO3 substrate using the MEMS technology. The pressure sensing structure was 3D-printed using polyactic acid plastic, and two SAW resonators were integrated in the 3D-printed chamber structure for both temperature and pressure sensing. The SAW-based gas pressure sensors demonstrate a sensitivity of 589 ppm/MPa at the pressure range of 100-600 kPa and temperature of 40 °C. [ABSTRACT FROM AUTHOR]

[Display omitted] • Interaction of β particles with ECSs was simulated using Monte Carlo method. • Quasi-solid electrolyte (QSE) is used to improve the long-term stability of the device. • A IL/gel-based QSE was used to improve the performances of EBV/EPV cells. • ZnO/CdS heterojunction enhances the electrochemical redox reactions. Electrochemical betavoltaic (EBV) cells are promising power sources for low-power electronics in remote and harsh environments. However, their practical applications are limited by the organic liquid electrolytes with the inferior temperature stability and narrow electrochemical window. In this work, a quasi-solid-state EBV cell was fabricated using a high-conductive gel-based quasi-solid-electrolyte (QSE), a CdS-modificated ZnO nanorod arrays (ZNRAs) structure as the anode material, a radioactive 63Ni sheet as the cathode as well as the irradiation source. Monte Carlo (MC) simulations are utilized to determine the optimized length (2.97 μm) of the ZNRAs filled by electrolyte, Electrochemical photovoltaic (EPV) cells were used to assess and optimize the content of CdS loaded on the ZNRAs. The optimum EBV cell demonstrated an excellent long-term stability and a high energy-conversion efficiency of 10.09 % with a short-circuit current density of 0.755 μA cm−2 and an open-circuit voltage of 0.288 V. The porous CdS@ZNRAs core–shell structure filled by soft ionic liquids (IL)/gel-based QSE enables a large specific area of electrochemical interface network. The synergistic effects of 3-D CdS/ZnO heterostructure with type-II band alignment and IL/gel-based QSE are responsible for the enhanced ECE and improved long-term stability of EBV/EPV cells. [ABSTRACT FROM AUTHOR]

Abstract A comprehensive comparison study of the UV–visible photoresponse properties of non-aligned carbothermal ZnO nanowires (ZNWs) composited with reduced graphene oxide (RGO) and single-walled carbon nanotubes (SWCNTs) is presented. The RGO/ZNWs composites (GZWs) and SWCNTs/ZNWs composites (CZWs) have been successfully synthetized through UV-assisted photochemical reduction of GO in ZNWs suspension and ultrasonic stirring technology, respectively. The optimal contents of RGO and SWCNTs incorporated into ZNWs were determined for achieving maximum photoresponse, respectively. Experimentally, the optimal GZWs and CZWs exhibit significant enhancement in photoelectric properties than pure ZNWs. It is demonstrated that the GZWs-based photodetector has higher photoresponsivity (∼16 AW-1) than CZWs-based photodetector under low UV irradiation (<10 μWcm−2) and at 1.0 V bias, while the CZWs-based photodetector has higher on/off current ratio (8.41 × 104) and faster response time (1.99 s of rise-time and 0.39 s of decay-time) than GZWs-based one. The detail physics mechanism on the effects of RGO and SWCNTs on photoelectric characteristics of ZNWs is presented with the interface charge transfer due to the chemisorption and photo-desorption of oxygen. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

An intertwined single-walled carbon nanotubes (SWCNTs)/carbothermal ZnO nanowires (ZNWs) composite is synthesized using a facile ultrasonic stirring technology, which is deposited on Au-interdigitated electrodes for ultraviolet-visible (UV-Vis) photoresponse enhancement. It is found that the SWCNT attached on ZNW surface optimizes the surface-related chemical processes and provides effective carrier transport strategies, responsible for the improvement in photo-responsivity and photo-sensing speed. The UV-Vis absorption of ZNWs has been improved after compositing with the high-conductive SWCNTs, contributing to the significantly improved photo-conductance. The photodetector based on SWCNT/ZNW composites (CZWs) with an optimal SWCNT content of 0.1 wt% shows a 300% improvement in photocurrent density, a 200% improvement in responsivity, and a 400% improvement in on/off current ratio over the pure ZNWs-based device under a UV irradiation of 3.26 mW cm−2 and a bias voltage of 1.0 V. This synthetic method could be scaled up for large-scale fabrication of CZWs on substrate at low cost for practical photodetecting applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A Si-based microchannel heatsink was used to improve the transient response characteristics of IR emitter. • A 3-D FEM was used to analyze the electrical-thermal and heat transfer behaviors of devices. • The devices performance can be improved when the flow velocity of coolant is larger than 0.5 m/s. Structure design and thermal simulation of MEMS-based thermal infrared (TIR) emitter integrated with Si-based microchannel heatsink (MCHS) were presented for gas sensing application. The MCHS attached on the bottom of TIR emitter was used to transfer heat to coolant for improving the transient response characteristics of TIR emitters. A three-dimensional finite element method was used to analyze the electrical heating and heat transfer behaviors of the TIR emitter with MCHS through COMSOL Multiphysics® platform. The surface temperature distribution and transient response were simulated when different flow velocities of coolant passed through the MCHS, and the influence of the flow velocity on the response characteristics was analyzed. The result shows that the temperature in the Si frame of TIR emitters will be significant reduced when the flow velocity of coolant is larger than 0.5 m/s, which will enable an effective improvement in the response characteristics of MEMS TIR emitters. [ABSTRACT FROM AUTHOR]

2-Dimensional (2D) wide band-gap semiconductor molybdenum disulfide (MoS2) nanosheets as an ultraviolet (UV) photo-conductive material were used in surface acoustic wave (SAW) resonators for UV light sensing. A SAW resonator based on zinc oxide (ZnO) piezoelectric film deposited on glass through radio frequency (RF) magnetron sputtering technique was prepared, in which the sub-microscale gold/chromium (Au/Cr) interdigital transducers (IDTs) and grating reflectors were fabricated onto the ZnO surfaces using the electron beam lithography and lift-off techniques to form the IDTs/ZnO/glass-based SAW resonator with a working frequency at ∼1.02 GHz. The MoS 2 nanosheets prepared by electrochemical lithiation process were coated on IDTs region to form a highly sensitive SAW UV sensor, exhibiting an interesting photoresponse behavior to UV radiation. A maximum frequency shift of ∼3.5 MHz was found under 365 nm UV radiation with power intensity of 1.466 mW/cm 2 , which is attributed to the high resonant frequency (in GHz) and high specific surface area of photo-conductive MoS 2 nanosheets. It is suggested that the adsorption and desorption of oxygen on MoS 2 nanosheets play the dominant roles in the frequency-upshift due to mass loading effect and acoustoelectric effect, meanwhile, acoustoelectric effect also creates the SAW attenuation. [ABSTRACT FROM AUTHOR]

The weak photon absorption and high recombination rate of electron-hole pairs in disordered zinc oxide nanowires (ZNWs) limit its application in UV photodetection. This limitation can be overcome by introducing graphene sheets to the ZNWs. Herein we report a high-performance photodetector based on one-dimensional (1D) wide band-gap semiconductor disordered ZNWs composited with reduced graphene oxide (RGO) for ultraviolet (UV) photoresponse enhancement. The RGO/ZNWs composites have been successfully synthetized through UV-assisted photochemical reduction of GO in ZNWs suspension. The material characterizations in morphology, Raman scattering, and Ultraviolet-visible light absorption verified the formation of graphene sheets attached in ZNWs network and the enhancement of UV absorption due to the introduction of graphene. In comparison with photodetectors based on pure ZNWs, the photodetectors based on RGO/ZNWs composite exhibit enhanced photoresponse with photocurrent density of 5.87 mA•cm-2, on/off current ratio of 3.01 x 104, and responsivity of 1.83 A•W-1 when a UV irradiation of 3.26 mW•cm-2 and 1.0 V bias were used. Theory analysis is also presented to get insight into the inherent mechanisms of separation and transportation of photo-excited carriers in RGO/ZNWs composite. [ABSTRACT FROM AUTHOR]

[Display omitted] • Interaction of beta particles with ECSs was simulated using Monte Carlo method. • ZrO 2 @Ar-TNRAs structure was used as the beta-anode of EBCs. • Photoelectrochemical performance was used to optimize the ECSs. • TiO 2 /ZrO 2 heterojunction with type-I band alignment can enhance the electrochemical redox reaction. Direct energy conversion from beta radiation to electricity using betavoltaic effect is a promising energy conversion technology for a long-time and highly efficient power supply. This work presents an electrochemical betavoltaic cell (EBC), consisting of a beta-anode with TiO 2 nanorod arrays (TNRAs) modified with ZrO 2 nanoparticles, a polyiodide (I −/ I 3 −) electrolyte, and a 63Ni/Ni counter electrode. Free-standing TNRAs structures were fabricated using hydrothermal method and post-annealed in Ar atmosphere to enable a rutile TiO 2 material with excellent electrochemical performance. Monte Carlo (MC) method was used to determine the optimum length (∼2.5 μm) of the TiO 2 nanorods. Investigation on ultraviolet photoelectrochemical performance of EBCs was used to evaluate and optimize the content of ZrO 2 (thickness of ∼10 nm) modified on the TNRAs. The EBCs demonstrated an energy conversion efficiency of 9.27% with an open-circuit voltage of 0.276 V and short-circuit current density of 1.041 μA·cm−2 when using a 10 mCi 63Ni source. The enhanced performance can be ascribed to the three-dimensional ZrO 2 /TiO 2 heterojunction with a large specific area in favor of the interface carrier transfer as well as the suppression of carrier recombination through the type-I band barrier, effectively promoting the electrochemical redox reaction. [ABSTRACT FROM AUTHOR]

This article presents a compact piezoelectric vibration energy harvester (VEH) using multiple nonlinear techniques to tuning the resonant frequency and broadening the bandwidth. The device was designed as a parallel-plate structure consisting of a suspended spring-plate with proof mass and piezoelectric transducers, a tunable stopper-plate, and supporting frames. By mechanical adjusting the vertical gap between the spring-plate and the stopper-plate (GBSS), the VEH can realize tuning of the resonant frequency and the bandwidth by multiple nonlinear effects. Experimentally, the piezoelectric VEH was assembled as a metal prototype that can be operated in three kinds of work states corresponding to the configurations of large-GBSS, small-GBSS, and over-GBSS. The sweeping-frequency measurement results show that the work frequency, bandwidth, and output-voltage of VEH depend on tuning of GBSS and excitation levels, indicating that the multiple nonlinear effects, such as Duffing-spring effect, impact effect, preload effect, and air elastic effect, have significant influence on the dynamic behaviors of VEH. The comparisons of numerical simulations with the experimental results were used to verify the validity of mathematical modeling on VEH with multiple nonlinear tuning techniques. [ABSTRACT FROM AUTHOR]

Highly efficient direct energy conversion utilizing the betavoltaic effect is a promising alternative for developing of maintenance-free and long-life self-generating power cells. This work demonstrates a betavoltaic-powered electrochemical cell (BPEC) using free-standing TiO 2 nanotube arrays (TNTAs) incorporated with single-wall carbon nanotubes (SWCNTs) as the beta anode, a polyiodide (I − / I 3 − ) solution as the electrolyte, and a radioisotope 63Ni/Ni sheet as the cathode as well as the irradiation source. Freestanding TNTAs were fabricated using electrochemical anodization. Monte Carlo simulations were used to investigate the interaction of the incident beta particles with the TNTAs structure. Experimentally, the photoelectrochemical characteristics were used to optimize the structural design of the BPECs. The optimum BPEC exhibited an energy conversion efficiency of 8.74% with an open circuit voltage of 0.26 V and a short circuit current density of 0.87 μA/cm2. The enhanced betavoltaic effect is attributed to the highly efficient separation and transport of beta-generated carriers through the enhanced beta-electrochemical redox reactions in the 3-D TiO 2 /liquid heterojunction as well as the extensive SWCNTs conductive network. [Display omitted] • Monte Carlo simulation is used to investigate the interaction of beta particles with energy conversion structures. • TNTAs incorporated with SWCNTs were used as the beta-anode of BPECs. • Photoelectrochemical performance is used to evaluate and optimize the structure design of BPECs. • Beta-excited electrochemical reaction is enhanced by the 3-D TiO 2 /liquid heterojunction and SWCNTs conductive network. [ABSTRACT FROM AUTHOR]

This paper presents a passive wireless polymer-derived silicon carbonitride (SiCN) ceramic sensor based on cavity radio frequency resonator together with integrated slot antenna. The effect of the cavity sensor dimensions on the Q-factor and resonant frequency is investigated by numerical simulation. A sensor with optimal dimensions is designed and fabricated. It is demonstrated that the sensor signal can be wirelessly detected at distances up to 20 mm. Given the high-temperature stability of the SiCN, the sensor is very promising for high-temperature wireless sensing applications. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present the design and simulation of a p–n junction betavoltaic battery based on large-grain polysilicon. By the Monte Carlo simulation, the average penetration depth were obtained, according to which the optimal depletion region width was designed. The carriers transport model of large-grain polysilicon is used to determine the diffusion length of minority carrier. By optimizing the doping concentration, the maximum power conversion efficiency can be achieved to be 0.90% with a 10mCi/cm2 Ni-63 source radiation. [Copyright &y& Elsevier]

Developing effective catalysts for the degradation of organic pollutants in the water as well as water-splitting for hydrogen production by using solar energy is a promising and green route for utilization and protection of water resources. In this study, a mesoporous TiO 2 /CeO 2 (m- TiO 2 /CeO 2) nanocomposite aerogel was prepared and defect-engineered using a facile sol-gel method assisted solvent exchange and hydrogenated thermal treatment. The hydrogenated black m -TiO 2 /CeO 2 nanocomposite aerogel exhibits the enhanced photocatalytic activity in the degradation of Rhodamine B (Rh B) and water splitting under visible-light irradiation. The degradation rate of Rh B reached ~96.4% in 60 min, and the hydrogen-evolution rate reached ~182 mmol h−1g−1, which are far higher than those of air-annealed m -TiO 2 sample. The photocatalytic enhancement mechanisms can be attributed to multiple strategies, such as the large specific surface area, the enhanced conductivity, the generation of self-doped defects in Z-scheme m -TiO 2 /TiO 2- x /CeO 2- x heterojunction, which are beneficial for providing more active sites, extending the absorption range of solar light, and suppressing the recombination of photo-excited carriers. [Display omitted] • The defect-engineered m -TiO 2 /CeO 2 aerogel was prepared using sol-gel method and hydrogenated thermal treatment. • The self-doped defects extend the visible light absorption of black m -TiO 2 /CeO 2 aerogel. • The migration of photoexcited charges in the m -TiO 2 /TiO 2- x /CeO 2- x heterojunction follow Z-scheme mechanism. [ABSTRACT FROM AUTHOR]