Papers by Keyword: Metal-Oxide-Semiconductor (MOS)

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Authors: Akira Uedono, Long Wei, Y. Tabuki, H. Kondo, Shoichiro Tanigawa, Y. Ohji
Authors: Ravi Chand Singh, Manmeet Pal Singh, Hardev Singh Virk
Abstract: Gas detection instruments are increasingly needed for industrial health and safety, environmental monitoring, and process control. To meet this demand, considerable research into new sensors is underway, including efforts to enhance the performance of traditional devices, such as resistive metal oxide sensors, through nanoengineering. The resistance of semiconductors is affected by the gaseous ambient. The semiconducting metal oxides based gas sensors exploit this phenomenon. Physical chemistry of solid metal surfaces plays a dominant role in controlling the gas sensing characteristics. Metal oxide sensors have been utilized for several decades for low-cost detection of combustible and toxic gases. Recent advances in nanomaterials provide the opportunity to dramatically increase the response of these materials, as their performance is directly related to exposed surface volume. Proper control of grain size remains a key challenge for high sensor performance. Nanoparticles of SnO2 have been synthesized through chemical route at 5, 25 and 50°C. The synthesized particles were sintered at 400, 600 and 800°C and their structural and morphological analysis was carried out using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The reaction temperature is found to be playing a critical role in controlling nanostructure sizes as well as agglomeration. It has been observed that particle synthesized at 5 and 50°C are smaller and less agglomerated as compared to the particles prepared at 25°C. The studies revealed that particle size and agglomeration increases with increase in sintering temperature. Thick films gas sensors were fabricated using synthesized tin dioxide powder and sensing response of all the sensors to ethanol vapors was investigated at different temperatures and concentrations. The investigations revealed that sensing response of SnO2 nanoparticles is size dependent and smaller particles display higher sensitivity. Table of Contents
Authors: Jean-Jacques Delaunay, I. Nagatomo, R. Uchino, Y.B. Li, M. Shuzo, I. Yamada
Abstract: Layers of ZnO micro-nano structures were deposited on quartz substrates and subsequently plasma treated in O2 and N2. It was found that exposure to O2 plasma enhanced gas response to ethanol vapor of the ZnO layers by a factor 8, while exposure to N2 plasma deteriorated the gas response. This enhancement of the gas response upon O2 plasma treatment was attributed to the formation of nanocrystallites of ZnO on the original ZnO micro-nano structures which form the gas sensing layers. The surface chemical state of the original sample was found to be not affected by the O2 plasma while it was modified by the N2 treatment.
Authors: Daniel J. Lichtenwalner, Lin Cheng, Sarit Dhar, Anant K. Agarwal, Scott Allen, John W. Palmour
Abstract: Alkali (Rb, Cs) and alkaline earth elements (Sr, Ba) provide SiO2/SiC interface conditions suitable for obtaining high metal-oxide-semiconductor field-effect-transistor (MOSFET) channel mobility on the 4H-SiC Si-face (0001), without the standard nitric oxide (NO) anneal. The alkali elements Rb and Cs result in field-effect mobility (μFE) values >25 cm2/V.s, and the alkaline earth elements Sr and Ba resulted in higher μFE values of 40 and 85 cm2/V.s, respectively. The Ba-modified MOSFETs show a slight decrease in mobility with heating to 150 °C, as expected when mobility is not interface-trap-limited, but phonon-scattering-limited. The interface state density is lower than that obtained with nitric oxide (NO) passivation. Devices with a Ba interface layer maintain stable mobility and threshold voltage under ±2 MV/cm gate bias stress at 175 °C, indicating no mobile ions.
Authors: Takeshi Ohshima, Masahito Yoshikawa, Hisayoshi Itoh, Kazutoshi Kojima, Sohei Okada, Isamu Nashiyama
Authors: Manato Deki, Takahiro Makino, Kazutoshi Kojima, Takuro Tomita, Takeshi Ohshima
Abstract: The critical electric field (Ecr) of the gate oxide in 4H-Silicon Carbide (SiC) MOSFETs was measured under inversion bias conditions with ion irradiation. The Linear Energy Transfer (LET) dependence of the Ecr at which the gate oxide breakdown occurred in these MOSFETs was evaluated. The linear relationship between the Ecr-1 and LET was observed for SiC MOSFETs. The slope of the LET-1/Ecr for SiC MOSFETs is almost the same that of the LET-1/Ecr lines for SiC MOS capacitors. The Vds dependence of Ecr was also evaluated. The correlation between the direction of electric field of drain-source region and direction of ion incidence affects to instability of Ecr.
Authors: Xiao Ying Chang, Qian Qiong Wu
Abstract: Al doped zinc oxide (AZO) as anode for bulk-heterojunction [regioregular of poly(3-hexylthiophene) (P3HT):(6,6)-phenyl C61 butyric acid methyl ester (PCBM)] organic solar cells was investigated. We got efficient flexible solar cells with a highly transparent and electrical conductive NiO film as hole-transporting layer (HTL) on optimized AZO substrate. The strcture of this kind of devices is PET/AZO/NiO/P3HT: PCBM /Al. The highest power conversion efficiency (PCE) on glass substrate is 3.15%, and 1.66% on flexible substrate. The physical and electrical properties of AZO thin film were discussed, and the device photovoltaic characteristics were investigated in detail.
Authors: Wen An, Chun Ying Yang
Abstract: New progress of research on the preparation technique of micro gas sensors of metal oxide semiconductors is introduced, such as the chemical treatment of the gas sensing film, the deposited technique of gas sensing film in the oxygen radical assisted EB evaporation, the technique of the multilayered film, the fabrication technique of the thermally oxidized, the technique of the electrode configuration, the fabrication technique of the miniaturized arrays by micro-molding in capillaries, the dip-coating of the sol-gel. And their features will be analyzed respectively, and their existing problems and future development directions will be given.
Authors: Amir Amini, Khachik Babaians, Mohsen Gharesi
Abstract: Detection of highly ppm range hydrogen concentration in atmospheres contaminated with various volatile organic compounds is in demand for numerous applications. Different devices and techniques have been applied for the problems which are mostly based on utilization of hydrogen permeable membranes. Here, we have used a single generic metal oxide gas sensor for this task. No filter or membrane is utilized. The operating temperature of the sensor is modulated with a voltage waveform specifically designed for producing step-like temperature changes on the oxide pallet. By applying four different step-like temperature jumps, each of 1s duration, the sensor produces response patterns which are processed with common pattern recognition techniques. The technique was examined by its practical use for the ~10 ppm (volume) hydrogen measurement in a background containing ~1000 ppm ethanol. The analysis takes only 4s, and the obtained patterns are reproducible.
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