Synthesis and characterization of high-quality In 2 O 3 nanobelts via catalyst-free growth using a simple physical vapor deposition at low temperature J.S. Jeong a , J.Y. Lee a, * , C.J. Lee b , S.J. An c , G.-C. Yi c a Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Republic of Korea b Department of Nanotechnology, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Republic of Korea c Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), San-31 Hyoja-dong, Pohang 790-784, Republic of Korea Received 23 October 2003; in final form 5 December 2003 Published online: 29 December 2003 Abstract High-quality indium oxide (In 2 O 3 ) nanobelts were successfully synthesized without catalyst at low temperature ranged from 600 to 850 °C using a simple physical vapor deposition. To synthesize the In 2 O 3 nanobelts, we employed a simple reaction of thermally evaporated indium vapor in a wet oxidizing environment. The In 2 O 3 nanobelts have diameters in the range of 20–200 nm and lengths over several hundreds micrometer. The synthesized nanobelts indicate high-purity and single-crystalline cubic structure. Most of In 2 O 3 nanobelts have h100i growth direction but some nanobelts have h110i growth direction. Photoluminescence spectra under excitation at 325 nm showed a strong and broad emission at 570 nm with a shoulder at 630 nm related to oxygen vacancies. We suggest that the synthesis of the In 2 O 3 nanobelts follows the self-assisted growth mechanism in our method. Ó 2003 Published by Elsevier B.V. 1. Introduction Recently, one-dimensional (1D) semiconducting nanostructures, such as nanowires and nanobelts, have attracted much attention because of potential applica- tions in various areas, such as material sciences, elec- tronics, optics, magnetism and energy storage due to their special properties distinctive from conventional bulk materials [1–4]. 1D nanostructures of various sys- tems, such as Si, Ge, GaAs, and GaN had been suc- cessfully synthesized by various methods, including laser-ablation, template-based method, arc discharge, and vapor-transport process [1,3–6]. As well as semiconductor nanostructures, it has been expected that semiconducting oxide nanostructures can promise various applications due to their interesting optical, electrical, and magnetic properties. Recently, nanowires and nanobelts of several binary oxide sys- tems, including Ga 2 O 3 , ZnO, MgO, SnO 2 , CdO and In 2 O 3 have been successfully synthesized [7–17]. Among them, the In 2 O 3 , which is a wide band gap transparent semiconducting material, has been widely used in the microelectronic applications including win- dow heaters, solar cells, and liquid-crystal displays [17– 19]. Up to the present, the In 2 O 3 nanowires and nano- belts have been synthesized by several techniques, such as rapid heating of InP substrate coated with a thin Au layer [17], oxidation of indium metal embedded by electrodeposition in anodic alumina membranes [19], thermal evaporation of indium source materials [16,20], and direct hydrogen reduction of In 2 O 3 powder with Ag nanoparticles as catalyst [21]. Most recently, diameter- controlled growth of the In 2 O 3 nanowires have been achieved on Si/SiO 2 substrate covered with Au film as catalyst by the laser-ablation of InAs target [22,23], and * Corresponding author. Fax: +82-42-869-4276. E-mail address: j.y.lee@kaist.ac.kr (J.Y. Lee). 0009-2614/$ - see front matter Ó 2003 Published by Elsevier B.V. doi:10.1016/j.cplett.2003.12.027 Chemical Physics Letters 384 (2004) 246–250 www.elsevier.com/locate/cplett