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Multifunctional monoclinic VO2 nanorod thin films for enhanced energy applications: Photoelectrochemical water splitting and supercapacitor
摘要： Monoclinic VO2 nanorod thin films were deposited on indium?tin-oxide-coated glass substrates using radio-frequency reactive magnetron sputtering at a substrate temperature of 300 °C and various O2 flow rates. The thin films were characterized via standard analysis techniques. The VO2 thin films exhibited a highly crystalline monoclinic phase with an indirect band gap of ~1.73 eV. At optimized O2 flow rate (4 sccm), the thin films was observed nanorod structures, exhibited a remarkable photocurrent of ~0.08 mA cm?2 during photoelectrochemical water splitting in the visible region. Electrochemical performance tests of the nanorod films revealed a specific capacitance of ~486 mF cm?2 at a scan rate of 10 mVs?1. In addition, amperometric I–t curves showed that VO2 thin film electrodes were highly stable during the photo-oxidation process. The nanorod films also exhibited a good specific capacitance of ~120 mF cm?2 after 5000 cycles at a scan rate of 100 mVs?1. The photocurrents during photoelectrochemical water splitting and the specific capacitance of VO2 thin films deposited at O2 flow rates of 2 and 6 sccm were 0.06 and 0.07 mA cm?2 and 398 and 37 mF cm?2, respectively. The films deposited under Ar at 8 sccm and O2 at 4 sccm showed the highest photoelectrochemical water splitting performance and specific capacitance, owing mainly to their nanorod-like morphology.
关键词： Supercapacitor,Partial pressure,Reactive sputtering,Photoelectrochemical water splitting,VO2,Monoclinic
更新于2025-09-23 15:22:29
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Retraction： Wetting Behavior of Single Crystal TiO<sub>2</sub> by Liquid Iron
摘要： The wetting behavior of TiO2 by liquid iron was investigated by using the sessile drop method. A partial melting behavior was found to appear at the temperature below the melting point of the pure iron. Also a solid solution TiOx–FeO phase was observed between the pure iron and TiO2 substrate. The formation of this reaction layer is due to the reaction among the pure iron, TiO2 substrate and the oxygen gas. The main source of the oxygen gas for reaction is from the TiO2 substrate decomposition and a low partial pressure of oxygen near the sample.
关键词： TiO2,wettability,partial pressure oxygen,decomposition
更新于2025-09-23 15:22:29
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Improvements in the synaptic operations of ferroelectric field-effect transistors using Hf <sub/>0.5</sub> Zr <sub/>0.5</sub> O <sub/>2</sub> thin films controlled by oxygen partial pressures during the sputtering deposition process
摘要： To control the polarization switching characteristics of ferroelectric HfxZr1?xO2 (HZO) thin films, the effects of oxygen partial pressure (PO2) during the sputtering deposition of HZO and the area ratio (SI/SF) of metal–ferroelectric–metal–insulator–semiconductor (MFMIS) gate stacks were investigated for ferroelectric synapse transistors. An increase in PO2 resulted in a relative decrease in the ferroelectric orthorhombic phase owing to the compensation of oxygen vacancies into the HZO films. The introduction of an MFMIS gate stack with a smaller SI/SF ratio effectively reduced the electric field applied across the HZO gate insulator. The polarization switching times for the HZO thin films could be modulated in a wide range by means of these two strategies, which were clearly examined to facilitate the synaptic operations of ferroelectric field-effect transistors (FeFETs) using HZO gate insulators. Typical synaptic operations, including paired-pulse facilitation and spike timing-dependent plasticity, were clearly demonstrated to exhibit gradual modulations of the channel conductance of the FeFETs with the evolution of spike signals, and these behaviors were enhanced upon increasing PO2 and decreasing the SI/SF ratio by controlling the switching kinetics of the ferroelectric partial polarizations of the HZO gate insulators in the proposed synapse FeFETs.
关键词： oxygen partial pressure,ferroelectric,Hf0.5Zr0.5O2,sputtering deposition,MFMIS gate stacks,synaptic operations
更新于2025-09-23 15:21:01
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Effect of selenium partial pressure on the performance of Cu2ZnSn(S, Se)4 solar cells
摘要： Sputtering followed by selenization is one of the most common methods for preparing CZTSSe thin films. However, the influence of selenium partial pressure on the crystallinity of the CZTSSe film has been rarely reported. In this study, CZTSSe thin films were prepared by selenization using quartz tubes of different lengths. The influence of Se saturated vapor pressure and temperature on the structure, composition, optical, and electrical properties of CZTSSe films and solar cells was analyzed and these results were used to optimize the performance of the CZTSSe film. It was found that the maximum partial pressure of selenium was 22,542 Pa when the selenization process was carried out in a quartz tube with a length of 30 cm, which largely improved the structural and electrical properties of CZTSSe. However, quartz tube with an over-short length would bring strong partial pressure during selenization, which resulted in a generation of secondary phases. Finally, CZTSSe thin-film solar cell with a maximum efficiency of 3.27% was obtained at an optimal selenium partial pressure of 22542 Pa.
关键词： CZTSSe,thin-film solar cells,selenium partial pressure,selenization
更新于2025-09-23 15:19:57
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Oxygen partial pressure dependent UV photodetector performance of WO3 sputtered thin films
摘要： The influence of oxygen partial pressure (pO2) on the ultra-violet (UV) photodetector performance of WO3 thin films was studied. Here, the thickness of the WO3 thin films decreased from 225 nm to 150 nm with increasing the pO2 from 5% to 20%. The crystallinity of WO3 films decreased at higher pO2. The XPS analysis confirmed that the WO3 film deposited at 10% of pO2 had the more oxygen vacancies. The grain size of WO3 films decreased at higher pO2 grown conditions owing to the fragmentation of the oxide formation through the plasma. From current-voltage (I-V) measurements of WO3/Ti device, the ohmic-contact implies the formation of the metal-semiconductor junction with very less barrier height (?B) and it helps to the trapping of generated electrons for potential photodetector. Due to the higher number of incoming photons, the photocurrent was found to be increased as the power density increases. Finally, the WO3 film deposited at 10% of pO2 exhibits the higher photocurrent and quick rising time and hence this optimized thin film is suitable for UV-A photodetector.
关键词： Response time,WO3 film,Detectivity,Oxygen partial pressure,Photocurrent
更新于2025-09-19 17:13:59
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Oxygen Vacancy Controlled SiZnSnO Thina??Film Inverters with High Gain
摘要： Amorphous SiZnSnO (a-SZTO) thin film are succesfully deposited to control the electrical characteristics by changing the oxygen partial pressure [p(O2)] ratio during the deposition. As the p(O2) ratio increase, the on current, off current, and the field effect mobility (μFE) decrease and the threshold voltage (Vth) shift to the positive direction, gradually. This phenomenon occurred because the oxygen vacancies (VO) in the channel were suppressed due to the effect of oxygen injected during the deposition. To explore the possibility that the device can be applied to integrated thin film circuit and operate well in the application, the n-type only inverters are fabricated using VO controlled thin film transistors (TFTs). All inverters have clear voltage transfer characteristics (VTC) and well operated in the range of 3 V to 15 V of VDD. When Vth shift to positive direction in enhancement mode (E-mode), the voltage transition region (Vtr) of the inverter also shift to positive direction. The highest voltage gain is measured to be about 26.554 V/V at 15 V of VDD. It is proposed to be able to fabricate the inverters and control the transition value of VTC of the inverter simply by changing p(O2) ratio of E-mode TFT.
关键词： thin film transistors,n-type,amorphous oxide semiconductors,oxygen partial pressure
更新于2025-09-19 17:13:59
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The effects of the oxygen content on the photoelectrochemical properties of LaFeO3 perovskite thin films obtained by pulsed laser deposition
摘要： The physical properties of perovskite oxides are strongly influenced by their stoichiometry and one of the key features of these materials is the tunability of their functionality by controlling the interplay between the compositional and structural properties. Here, the effects on the photoelectrochemical (PEC) water splitting properties of ferroelectric LaFeO3 thin films obtained at different oxygen partial pressures during growth are reported in conjunction with the morphological, optical and structural features. The LaFeO3 thin films have been deposited by pulsed laser deposition on Nb:SrTiO3 substrates. The strong dependence of the photocurrent values Jphoto on the growth conditions is revealed by the photoelectrochemical measurements. Strong variations of the lateral coherence lengths L‖ of LaFeO3/Nb:SrTiO3 with the oxygen partial pressure values are noticed from the X-ray diffraction (XRD) analysis. All the films are heteroepitaxial with small tensile strain levels detected in the crystalline structure, but only for a narrow interval of oxygen partial pressures the LFO/STON thin films show high quality crystalline structure with large lateral coherence length L‖ and photoelectrochemical currents.
关键词： oxygen partial pressure,perovskite oxides,photoelectrochemical,pulsed laser deposition,water splitting
更新于2025-09-12 10:27:22
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Enhanced superconducting properties of a YGBCO/Gd-CeO2/YGBCO tri-layer film deposited by pulsed laser deposition
摘要： To evaluate the inhibition of the REBa2Cu3O7-δ (REBCO, where RE is rare earth) film thickness effect, a series of Y0.5Gd0.5Ba2Cu3O7-δ(YGBCO)/interlayer/YGBCO tri-layer films with Gd-Cerium oxide (CeO2) film were prepared under different experimental conditions in this study. The results illustrate that the electric current from the top YGBCO layer could transmit to the bottom YGBCO layer by adding Gd into the CeO2 interlayer with the approximate thicknesses limits of 10 nm. For further increase the electric current carrying capacity, a series of YGBCO/Gd-CeO2/YGBCO tri-layers were fabricated under different oxygen partial pressures and laser energies. The better crystallinity, and texture, and the smoother surface levels completely eliminated the thickness effect. However, the samples’ superconductivity declined sharply at low laser energies. Because the Gd particles deposited on the substrate were fully oxidized, this led to particle disappearance in the interlayer film. Additionally, YGBCO samples with a Gd-CeO2 interlayer were more likely to be damaged than a pure YGBCO sample in the measurement process, which could be solved by increasing the Gd content in the CeO2+Gd target. Hence, by depositing a Gd-CeO2 interlayer, YGBCO tri-layer films with high superconductivity and low damageability were obtained.
关键词： Gd-CeO2 interlayer,laser energy,superconductivity,damageability,oxygen partial pressure
更新于2025-09-11 14:15:04
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Hydrogen sensor for parabolic trough expansion tanks
摘要： The National Renewable Energy Laboratory and Acciona Energy North America are developing and implementing a process that addresses the issue of hydrogen buildup in parabolic trough power plants. We are pursuing a method that selectively removes hydrogen from the expansion tanks of the power plant to control hydrogen levels in the circulating heat-transfer fluid. As part of this effort, we are developing a sensor that measures hydrogen partial pressure in the expansion-tank headspace gas. During previous work, we demonstrated that our sensor design measures hydrogen levels over a wide partial pressure range from 1.33 mbar down to 0.003 mbar with an accuracy of ±20%. We acquired these results under limited conditions because we measured hydrogen partial pressure in gas mixtures of hydrogen and nitrogen only. In this paper, we report our most recent results in which we measured hydrogen partial pressures in gas mixtures that contain hydrogen, nitrogen, biphenyl, and diphenylether. Our results for this gas mixture were essentially the same as those obtained for the hydrogen/nitrogen mixture only, and they also had the same accuracy of ±20%. This level of accuracy is sufficient to evaluate the performance of a hydrogen mitigation process because hydrogen partial pressure in the expansion tank decreases more than an order of magnitude when the mitigation process is operating. We examined the palladium/silver membrane after completing these measurements and did not observe any signs of membrane deterioration or contamination due to exposure to biphenyl and diphenylether at 405oC. The membrane for these tests was 25 μm thick. For the next sensor design that we are developing in 2018, we are using a membrane that is 127 μm thick. This thickness is required for the membrane to withstand the 150 psi pressure drop across the membrane when exposed to actual headspace gas from the expansion tank. We performed initial tests in which we exposed a 127-μm-thick palladium alloy membrane to 400oC and 150 psi pressure drop and observed no signs of failure or gas leakage. Finally, we developed a transient model that accounts for hydrogen transport mechanisms within the sensor when measurements are made. Our model accounted for hydrogen diffusion through the boundary layer that is adjacent to the membrane and for hydrogen permeation across the membrane and into the permeate volume. Our modeling results agreed very closely with our experimental data when we assumed a boundary-layer thickness of 0.2 cm. This thickness is within the range of expected thicknesses for this gas composition, temperature, and pressure at minimum flowrate. Our model results showed that hydrogen diffusion through the boundary layer adjacent to the membrane is the rate-determining step for the transient pressure response when measuring hydrogen partial pressure.
关键词： hydrogen partial pressure,palladium/silver membrane,parabolic trough,expansion tanks,hydrogen sensor
更新于2025-09-04 15:30:14