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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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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