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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]

A self-powering ultraviolet photodetector (UVPD) that effectively utilizes UV energy in an easy-to-implement way is an attractive alternative for the UV optical sensing and communication. Here we report a novel self-powered UVPD based on a face-to-face hybrid ZnO nanorod arrays (ZNRAs) nanostructure. Large-area free-standing ZNRAs have been grown on indium tin oxide (ITO) conductive glass and Ti substrates through a hydrothermal method. Different geometric dimension of ZNRAs/ITO and ZNRAs/Ti structures were designed to pair hybrid each other for achieving the optimum photoelectric performance. Experimentally, it is found that the optimum UVPD based on face-to-face hybrid ITO/ l -ZNRAs/ l -ZNRAs/Ti structure exhibits an enhancement of '1+1>2' in photoelectric conversion without applying any external DC voltage when compared with single-face ZNRAs-based UVPDs, and the optimum UVPD demonstrates a responsivity of 2.45 mA W−1 and on/off current ratio of 6.6 × 105 under a UV irradiation of 3.06 μW cm−2 as well as a high durability with a cyclic balance of no less than 93.5% in a 4250-s on/off irradiation. The generation of self-power and the high photoelectric performance of face-to-face hybrid ZNRAs-based UVPDs are associated to the Schottky junctions in ITO/ZnO interface as well as the extensive ZnO nanorod-nanorod homojunction. Image 1 • A self-powered Ultraviolet photodetector based on a novel face-to-face hybrid ZnO nanorod arrays (ZNRAs) nanostructure is presented. • The optimum face-to-face device exhibits '1+1>2' enhancement in photoelectric conversion when compared with single-face ZNRAs-based device. • The ZnO/ITO Schottky junction and extensive NR-NR homojunction facilitate the self-power generation and the high photoelectric performance. [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]

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]

[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]

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]

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]