Growth process of TiC clusters from Ti nanoparticles with evaporated carbon layer A. Ikegami a , Y. Kimura a, * , H. Suzuki a , T. Sato a , T. Tanigaki a , O. Kido a , M. Kurumada a , Y. Saito b , C. Kaito a a Department of Nanophysics in Frontier Project, Ritsumeikan University, Kaito-Lab, Kusatsu-shi, Shiga 525-8577, Japan b Department of Electronics and Information Science, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan Received 20 January 2003; accepted for publication 23 June 2003 Abstract Titanium carbide formation by the solid–solid reaction on the surface of Ti nanoparticles was studied in situ using a high-resolution transmission electron microscope with a heating stage. The cross-sectional image of the Ti surface was clearly observed. Vacuum-deposited carbon covered the whole the surface of Ti nanoparticles in spite of the partly evaporation on the nanoparticle surface. The diffusion of the carbon atoms inside the Ti nanoparticles depended on the size of the nanoparticles. When the Ti nanoparticle diameter was less than 30 nm, carbon atoms diffused into the Ti nanoparticle and formed TiC. The superstructure of the Ti nanoparticles was observed, which revealed the growth process of TiC to be the diffusion of carbon atoms. For Ti nanoparticles with diameter larger than 30 nm it was ob- served that diffusion of Ti atoms into the carbon layer was dominant, which resulted in formation of TiC in the carbon layer at the surface of Ti nanoparticles. Ó 2003 Elsevier B.V. All rights reserved. Keywords: Electron microscopy; Crystalline–amorphous interfaces; Clusters; Titanium carbide; Amorphous surfaces 1. Introduction Nanoscale behavior is not merely interesting for its science but also important for future material technology. We have shown that phases of tetra- taenite [1], enstatite [2] and spinel [3], which are commonly observed in minerals of interplanetary dust and/or carbonaceous chondrites, can be pro- duced by reactions between film and nanoparticles at relatively low temperatures. In the case of Si nanoparticles on a carbon film, amorphous silicon carbide is produced, even at room temperature by the diffusion of carbon atoms into Si nanoparticles [4]. The diffusion process during compound for- mation has been elucidated on the basis of mor- phological shapes of thin films and nanoparticles. Diffusion direction as a function of nanoparticle size was observed in some systems [5,6] and dis- cussed in terms of the problems of nanoparticle stability and electronegativity. In order to see the different phenomenon nature in the nanopar- ticle, the nanoparticle-cluster reaction has been * Corresponding author. Tel.: +81-77-561-2709; fax: +81-77- 561-3994. E-mail address: rp092955@se.ritsumei.ac.jp (Y. Kimura). 0039-6028/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0039-6028(03)00875-6 Surface Science 540 (2003) 395–400 www.elsevier.com/locate/susc