ZnO nanorods grown by a Pulsed Laser Deposition process
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ZnO nanorods grown by a Pulsed Laser Deposition process Jae-Hwan Park, Young-Jin Choi, Won-Jun Ko, In-Sung Whang, and Jae-Gwan Park Materials Science and Technology Division, Korea Institute of Science and Technology, PO Box 131, Cheongryang, Seoul 130-650, Korea ABSTRACT ZnO nanorods were synthesized by a hot-wall type pulsed laser ablation process. At temperatures 500~800oC, ZnO thin films and wrinkles were synthesized. Above 800oC, vertically aligned ZnO nanorods were grown on the Si and sapphire substrate without any catalysts. The range of diameter was 100~300nm. When Au catalyst were deposited on the substrate prior to the deposition, the process range of ZnO nanorod become wider and the diameter of ZnO narrower. Especially, ZnO could be grown selectively along the pattern of Au catalyst with the aid of Au-Zn alloy. INTRODUCTION One-dimensional (1-D) nanostructures have been extensively studied due to their potential as building blocks for nanoelectronics. Various semiconducting nanowires, nanorods, and nanotubes of single element, oxide, and compound semiconductors have been successfully synthesized (1-3). ZnO, a wide-bandgap (3.37 eV) semiconductor, has especially attracted considerable attention due to the potential applications for the electrooptics, electronics, and piezoelectrics. Thus, various 1-D nanostructures of ZnO including nanorods and nanotubes have been fabricated by several different processes (4-8). Typically, ZnO nanorods have been synthesized by a carbothermal reduction process (1,4), on an Au-coated silicon substrate by heating a 1:1 mixture of ZnO and graphite. For higher stability and large-area compatibility, metalorganic chemical vapor deposition (MOCVD) process has been used for fabrication of ZnO nanorods in the temperature range of 400~500oC. In this process, however, selective growth of nanorod by the aid of catalysts is difficult due to such a low process temperature. Pulsed-laser ablation (PLA) is also a very simple method and widely used for the synthesis of various thin films, especially in multicomponent systems (8~10). However, this method has been rarely reported in the synthesis of ZnO nanorod. Little research has been done regarding cold-wall PLA process in the temperature range 500~600oC (8). In this work, high-temperature hot-wall PLD process were developed for fabrication of narrow-sized ZnO nanorods and patterning, i. e. selective growth of nanorod with the aid of catalyst, of ZnO nanorod. EXPERIMENTAL DETAILS Sintered targets of ZnO were prepared from ZnO powders (High Purity Chem. Co., >99.9%,
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