Catalyst-free and controllable growth of SiC x N y nanorods L.C. Chen a, * , S.W. Chang b , C.S. Chang b , C.Y. Wen a , J-J. Wu c , Y.F. Chen b , Y.S. Huang d , K.H. Chen c a Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan b Department of Physics, National Taiwan University, Taipei, Taiwan c Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan d Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan Received 16 January 2001; accepted 19 January 2001 Abstract Non vapor±liquid±solid VLS) method of growing high-purity silicon carbon nitride SiC x N y ) nanorods with rod widths ranging from 10 to 60 nm and lengths of microns is reported. Unlike the case for the ordinary VLS or catalyst-mediated growth, the two-stage process presented here is a catalyst-free approach since it does not involve any catalyst during the growth of the nanorods. The ®rst stage involves formation of a buffer layer containing various densities of SiC x N y nanocrystals by electron cyclotron resonance plasma enhanced chemical vapor deposition PECVD); whereas the second stage involves a high growth rate along a preferred orientation to produce high-aspect-ratio nanorods using microwave PECVD. Moreover, the number density and the diameter of the nanorods can be controlled by the number density and the size of the nanocrystals in the buffer layer. Production of quasi-aligned SiC x N y nanorods with a number density of the rods as high as 10 10 cm 22 has been achieved. The SiC x N y nanorods thus produced exhibit good ®eld emission characteristics with stable operation over 8 h. The approach presented here provides a new advance to synthesize nanorod materials in a controllable manner. q 2001 Elsevier Science Ltd. All rights reserved. Keywords: A. Nanostructures; B. Vapor deposition 1. Introduction The inherent anisotropy in one-dimension 1-D) systems, such as nanotubes, nanorods, and nanowires, is central to the unique properties and phases of these materials [1]. Besides the quantum size effect [2], the lattice orientation in a nanorod or nanowire can affect their optical properties in a manner unavailable in quantum dots [3]. Applications for 1- D systems include functional components in advanced mesoscopic electronic and optical devices, interconnects, probe microscopy tips, as well as superstrong and tough composites [4±7]. Among them, electron ®eld emission of carbon nanotubes CNT) exhibits rather promising features for ¯at-panel-display application [8]. The extremely large ®eld enhancement effect originated from the sharp curvature of CNT is the main factor responsible for their low threshold ®elds and high current densities. In view of this, nanorods and nanowires with similar geometric features have the potential as ®eld emitters, and indeed good ®eld emission properties from these nanostructures have been reported [9± 11]. Nevertheless, researches on 1-D materials other than CNT are still quite scanty. To explore and realize these exciting opportunities requires producing 1-D system in a well-controlled manner. To date, several techniques, such as laser ablation [12,13], template-based [14,15], solution-based [16], carbothermal reduction [17], powder-mixture reaction [18] oxide-assisted growth [19], and rapid thermal process [20] have been employed to synthesize 1-D nanostructures. Most of the techniques relate to the vapor±liquid±solid VLS) process wherein a catalyst is involved. The catalyst usually remains in the 1-D system and may affect its intrinsic properties. Journal of Physics and Chemistry of Solids 62 2001) 1567±1576 0022-3697/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved. PII: S0022-369701)00096-8 www.elsevier.com/locate/jpcs * Corresponding author. Tel.: 1886-2-2366-8228; fax: 1886-2- 2362-0200. E-mail address: chenlc@ccms.ntu.edu.tw L.C. Chen).