Study of the Synthesis of WO 3 Nano-structured Arrays by Tungsten Hot Filament Chemical Vapor Deposition Method and their Field Emission Properties Di Lu, Bo Liang, Akihisa Ogino, Masaaki Nagatsu* Graduate School of Science and Technology, Shizuoka University, 3-5-, Johoku, Naka-ku, Hamamatsu, Shizuoka, Japan, 432-80 *e-mail: tmnagat@ipc.shizuoka.ac.jp Recently the inorganic semiconductor nanomaterials were of much interest for field emission (FE) applications. [] Tungsten tri-oxides (WO 3 ) is kown as an interesting semiconductor material for the electrohromic (EC) effect and numerous applications. [2] Nevertheless, the field emission (FE) properties from the WO 3 nano-wires array were also appealing and made it a potential material for the field emission application. There are two main methods by CVD method: () evaporation of WO 3 powder [3] and (2) oxidation of the heated tungsten [4] . Here in this work, the hot filament chemical vapor deposition method is adopted, with an extra heating stage is employed as well, to control the substrate temperature precisely. Since this method, different kinds of WO 3 nano-structure arrays were prepared, and their FE properties were studied. The tungsten hot filament chemical vapor deposition (HWCVD) method was used to grow nano-structured WO 3 under oxygen and argon gas mixture. A The cleaned silicon substrate (p-type [00]) was placed on the heating stage and heated up to 00°C~850°C in the Ar atmosphere (~0.5 Torr). Then the tungsten filament (0.mm) was applied a current and heated to more than 500°C. It also served as the tungsten source to synthesize nano-structured WO 3 composites when a gas flow of oxygen was introduced in addition to Ar. Typically, the gas ratio of O 2 /Ar was 2.5/98 sccm and the growth time was 2~5 min. According to our result, we found interesting growth mechanism of the WO 3 nano-structures. The WO 3 nano-rods arrays grown along the different crystal growth direction showed different field emission properties. The crystal growth direction could be controlled by tuning the substrate temperature. The morphology of the nano-structures grown at different substrate is showed in the Fig.. It can be found from the image that nano-rods array with the thinnest diameter is grown under 750°C. And micro-cone shape structures with sharp tips were grown at 850°C. Carbon nano-rods arrays were grown at substrate temperature of 700°C and 800°C. The field emission properties of these nano-structure WO 3 materials were measured and showed in the Fig.2. The result suggests that the WO 3 nano-rods grown at 750°C have the best field emission properties among these samples, with the turn on field about .5~2V/ μm. References [] Xiaosheng Fang, Yoshio Bando, Ujjal K. Gautam, et al J. Mater. Chem. 18, 509 (2008). [2] Satyen K. Deb, Solar Energy Materials and Solar Cells 92, 245 (2008). [3] Jun Zhou, Li Gong, Shao Zhi Deng, et al Appl. Phys. Lett. 87, 22308 (2005). [4] Jingguo Liu, Zhengjun Zhang, Ye Zhao, et al Small 1, 30 (2005). P2-A13 237 978--4244-3588-3/09/$25.00©2009 IEEE Techinical Digest of IVNC2009