Physica E 40 (2008) 2526–2530 Low-temperature synthesis of one-dimensional ZnO nanostructures on screen-printed carbon nanotube films Seung-Sik Park a , Jin-Moo Lee a , Seung-Il Yoon a , Dong-Gu Lee a , Sung-Jin Kim a , Sang-Hyeob Kim b , Sunglyul Maeng b , Sang-Woo Kim a,Ã a School of Advanced Materials and System Engineering, Kumoh National Institute of Technology, 1 Yangho-dong, Gumi, Gyeongbuk 730-701, Republic of Korea b Cambridge-ETRI Joint R&D Center, Electronics and Telecommunications Research Institute, 161 Gajeong-dong, Daejeon 305-700, Republic of Korea Available online 03 December 2007 Abstract One-dimensional (1D) ZnO nanostructures including nanowires, nanobelts, and nanorods were synthesized on screen-printed multi- walled carbon nanotube (MW-CNT) films in a thermal chemical vapor deposition process by gold (Au) nanoparticle-catalyst and self- catalyst driving at low temperatures of 400 and 500 1C. ZnO nanowires and nanobelts by introducing Au nanoparticles were grown via the vapor–liquid–solid (VLS) mechanism, while ZnO nanorods were realized via a self-catalytic VLS process. It was found that the diameter of ZnO nanowires strongly depends on that of Au nanoparticles, indicating the typical metal catalyst-driving VLS process. On the other hand, ZnO nanorods without Au-alloyed tips are comprised of hexagonal facets, suggesting self-catalytic VLS formation of the ZnO nanorods on the MW-CNT films. Room temperature photoluminescence spectra of the 1D ZnO nanostructures exhibit an ultraviolet emission band around 378 nm and deep-level emission band centered around 505 nm. r 2007 Elsevier B.V. All rights reserved. PACS: 81.07.Bc; 81.10.Bk; 78.55.Et Keywords: ZnO; One-dimensional nanostructures; CVD; Carbon nanotubes 1. Introduction Nanostructured materials have become one of the most intensively studied subjects over many years because of their realization in potential applications [1–3]. ZnO has been one of the most promising oxide semiconductor materials because of its good optical, electrical, and piezoelectric properties. It can be used in many areas such as field-emission displays, solar cells, and gas sensors [4–6]. ZnO has been recognized as one of the potential photonic materials in the ultraviolet region [7] because of its wide direct band gap (3.37 eV) and large exciton binding energy (60 meV). Recently, interesting optical properties in ZnO nanostructures, such as room temperature (RT) ultraviolet laser emission, have been demonstrated [8]. Various kinds of approaches have been introduced to synthesize low- dimensional ZnO nanostructures [9]. For example, thermal evaporation and condensation [10], aqueous solution deposition [11], metal organic chemical vapor deposition (CVD) [12,13], and laser molecular beam epitaxy [14] have been employed for fabrication of ZnO nanostructures including nanorods, nanowires, nanobelts, nanonails, nanodots, and quantum wells. In the above-mentioned processes, high growth temperature and long process time are generally required. The aqueous solution deposition method allows low-temperature growth of ZnO nanos- tructures, while a large number of defects are introduced into the nanostructures. Synthesis of ZnO nanostructures on metallic carbon nanotubes (CNTs) leads to semiconducting ZnO nanos- tructure/metallic CNT heterojunctions, which might be very useful in applications using nanoscale semiconductor- metal junction structures. Recently, Jo et al. [4] have reported distinguished field-emission properties of ZnO nanowires grown on carbon clothes. The ZnO nanowires ARTICLE IN PRESS www.elsevier.com/locate/physe 1386-9477/$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.physe.2007.11.026 Ã Corresponding author. Tel.: +82 54 478 7745; fax: +82 54 478 7769. E-mail address: kimsw@kumoh.ac.kr (S.-W. Kim).