Ahsanulhaq Qurashi

University of Toyama Repository

Synthesis of Characterization and Sensing properties of Metal-Oxide N anostructures 非常勤研究員 QurashiAhs姐 ulhaq1. Introduction One-dimensional (ID) metal-oxide semiconductor nanostructures have a位actedsignificant attention over the past decade due to their unique electronicヲopticalヲandmagnetic properties. Metal-oxide nanostructures represent building blocks for unctional device architectures [ 1 －・ 3].0neof the examples is provided by the extensive studies of indium oxide (In203). In203 is an important wide band gap (3.6 eV) and transparent semiconductor material with attractive optoelectronic properties. There is growing attention in the synthesis of In203 nanostruc加resdue to their diverse morphologiesラ interestingproperties and important potential applications in nanodevices. Here we report an efficient route for the temperature dependent synthesis of single-crystalline 1 D In203 nanostructures on Au-coated silicon substrate by chemical vapor deposition. The gas sensing properties toward hydrogen gas have been tested over a wide range of concen首ationsand operating temperatures. Also thermal oxidation of Ni and Ti into their native oxide nanostructures reported. 2. Experimental details The synthesis of In203 nanostruc旬reswas performed in a simple chemical vapor deposition (CVD) system. The quartz tube has a length of 80 cm and a diameter of 5 cm. Two removable rubber corks were fixed to both ends of the quartz tube with an inlet and outlet respectively. Argon gas was in首oducedinto the quartz tube企omone end and flowed out from the other end. In this experiment 0.3 g of high-purity indium grains (purity:99.99%) was placed on an alumina boat. A silicon wafer coated with an Au film with a thickness of 10 nm was placed above the In grainsラwithits surface directed towards the In grains. The tube chamber was purged for 30 min. with Ar gas (purity: 99.99%) at a rate of I 00 mL/min-1 and then the furnace was heated to 800°C at a rate of 25°C/min and kept at出istemperature for I h.After cooling to room tempera加工e,a uniform layer of yellow color product with high purity was deposited on the silicon wafer. In order to study extensively the effect of temperature on the morphology ofln203 nanostructures, the synthesis was also carried out at 700 and 900°C. Thermal oxidation of Ni and Ti metal foils in presence of oxygen atmosphere was carried out in horizontal tube furnace. The hydrogen sensing behavior of In203 nanowires and nanoneedles were investigated at different operating temperatures. Results and discussion: In203 nanostructures formed under different reaction temperature. It was found that reaction temperaぬrehad a profound effect on the morphology of In203 nanostructures.明弓1enthe reaction was carried out at 700°C In203 nanorods with variable diameters were formed. When the reaction temperature was increased to 800°C In203 nanowires were formed. In203 nanoneedles were formed 95 96 at 900°C. Detailed structural analysis was carried out for In203 nanostructures. On the basis of growth temperature a possible growth mechanism is proposed. Hydrogen gas sensors of In203 nanowires and nanoneedles are fabricated. Our results illustrates that the sensor response of In203 nanowires increases with the hydrogen concen佐ationand operating temperature. Considering the nanosized effect In203 nanowires showed better gas sensor response compared with the In203 nanoneedles and could be more promising in real device application. In addition to In203 nanostrutcures Ni and Ti metal foils were annealed at different reaction condition in horizontal tube furnace to fabricate their native oxides. A variety of NiOラandTi 02 nanostructures were formed by by changing the experimental conditions. Ti02 nanorods and nanowires were formed by selecting appropriate reaction conditions. In conclusion variety of In203, NiO and Ti02 nanostructures were formed in horizontal tube furnace by varying the experimental conditions. Detailed structural analysis was carried out to know the crystal structure and growth mechanism. In order to compare hydrogen gas sensors performance In203 nanowires and nanoneedles were investigated in details. Figure 1. Low and high magnification FESEM images ofln203 nanorods (a) and (b); nanowires (c) and (d); and nanoneedles (e) and (f). References: [I] D. ZhangヲC.Li, X. Liuラ S.Han, T. Tangヲ C.Zhou, Doping dependent NH3 sensing of indium oxide nanowires, Appl. Phys. Lett. 83 (2003) 1845. [2] Q. Ahsanulhaq, J.H. Kimラ YB.Hahn, Con町olledselective growth of ZnO nanorod arrays and their field emission properties, Nanotechnology 18 (2007) 485307. [3] A. Qurashi N. Tabet1 M. Faiz T. Yamazaki, Ultra-fast microwave synthesis of ZnO nanowires and their dynamic response toward hydrogen gas, Nanoscale Res. Lett. 4 (2009) 948・954.

Synthesis of Characterization and Sensing properties of Metal-Oxide Nanostructures

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Synthesis of Characterization and Sensing properties of Metal-Oxide Nanostructures

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