Journal of ELECTRONIC MATERIALS, Vol. 32, No. 11, 2003 Regular Issue Paper 1344 Semiconductor Nanowires Surrounded by Cylindrical Al 2 O 3 Shells BYUNGDON MIN, 1 JONG SOO LEE, 1 KYOUNGAH CHO, 1 JU WON HWANG, 1 HYUNSUK KIM, 1 MAN YOUNG SUNG, 1 SANGSIG KIM, 1,4 JEUNGHEE PARK, 2 HEE WON SEO, 2 SEUNG YONG BAE, 2 MOON-SOOK LEE, 3 SOON OH PARK, 3 and JOO-TAE MOON 3 1.—Department of Electrical Engineering, Korea University, Seoul 136-701, Korea. 2.—Department of Chemistry, Korea University, Jochiwon 339-700, Korea. 3.—Process Development Team, Semiconductor R&D Division, Samsung Electronics Co. Ltd., Yongin-City, Kyunggi-Do, Korea. 4.—E-mail: sangsig@korea.ac.kr The GaN, GaP, InP, Si 3 N 4 , SiO 2 /Si, SiC, and ZnO semiconductor nanowires were synthesized by a variety of growth methods, and they were wrapped cylin- drically with amorphous aluminum oxide (Al 2 O 3 ) shells. The Al 2 O 3 was deposited on these seven different semiconductor nanowires by atomic layer deposition (ALD) at a substrate temperature of 200°C using trimethylalu- minum (TMA) and distilled water (H 2 O). Transmission electron microscopy (TEM) images taken for the nanowires revealed that Al 2 O 3 cylindrical shells surround uniformly all these semiconductor nanowires. Our TEM study illus- trates that the ALD of Al 2 O 3 has an excellent capability to coat any semicon- ductor nanowires conformally; its coating capability is independent of the chemical component, lattice structure, and growth direction of the nanowires. This study suggests that the ALD of Al 2 O 3 on nanowires is one of the promising methods to prepare cylindrical dielectric shells in coaxially gated, nanowire field-effect transistors (FETs). Key words: Al 2 O 3 shells, nanowires, transmission electron microscopy (TEM) (Received February 12, 2003; accepted July 14, 2003) INTRODUCTION A variety of semiconductor nanowires have been investigated because of their great potential in the application of optical and electronic devices. 1,2 To realize the potential of optical and electronic de- vices using semiconductor nanowires, the protection of the nanowires from oxidation, nitrification, and wetting is of crucial importance; in ambient air, Si nanowires are oxidized to form SiO 2 layers surrounding themselves, and GaP nanowires are nitrified. 3 Coating of semiconductor nanowires is, therefore, required to retain their optical, electrical, and physical properties. Aluminum oxide (Al 2 O 3 ) exhibits many excellent electrical and optical properties including high dielectric constant, very low permeability of alkali ions, high thermal conductivity, and transparency over wide range of wavelength. 4–6 Because of these characteristic properties, there have been extensive attempts to use Al 2 O 3 in the fields of capacitor di- electrics and gate oxides in memory devices, insulat- ing layers in electroluminescent display devices, waveguide, and corrosion-resistant coating films on metals. 7 More recently, Al 2 O 3 barrier layers de- posited on Si by the atomic layer deposition (ALD) technique have been investigated to study electrical and reliability characteristics of Si/Al 2 O 3 /Si capaci- tor structures for the future application of dynamic random access memory. 8–10 The fabrication of a coaxially gated, nanowire field-effect transistor (FET) has been realized re- cently by Lauhon et al. 11 The coaxially gated, nanowire FET has drawn much attention because of its capacitance enhancement compared to planar gates used for nanowire FETs. In this FET, the active channel is a Ge shell, and the gate dielectric is a SiO x shell. The concept of the coaxially gated,