JOURNALOF CRYST GROW ELSEVIER Journal of Crystal Growth 236(2002)171-175 www.elsevier.com/locate/jcrysgro Nucleation behavior of silicon carbide whiskers grown by chemical vapor deposition Ing-Chi Leu", Min-Hsiung Ho Department of Materials Science and Engineering, National Cheng Kung Unicersity, 1, Ta-Shueh Rd, Tainan 701, Ta Received 16 October 2001; accepted 28 November 2001 Communicated by T hibiya Silicon carbide (SiC) whiskers as a kind of high strength fibrous material are commonly used as an effective reinforcing element for composite materials. The preparation and characterization of such high aspect ratio material are of great importance to the understanding of fundamental properties and potential industrial applications of whisker materials. In this study the growth of Sic whiskers by chemical vapor deposition(CVD)from the thermal decomposition of methyltrichlorosilane was performed on Ni-coated graphite substrates in a hot wall reactor with an emphasis on the study of the fundamental nucleation and growth characteristics of the whiskers. Since vapor-liquid- solid mechanism is found to be responsible for the growth of whiskers, the formation of the Ni catalyst and its subsequent evolution on whisker nucleation and growth is a subject of extensive research. Scanning electron microscope is employed to characterize the nucleation and growth of SiC whiskers. It is found that the incubation period fc whisker nucleation and growth to noticeable dimension depends on the size of the Ni particles. It takes about 3 min the first whisker to appear and about 8 min to complete the whole nucleation stage for the case of Ni-coating thickness of about 2.5 um under the CVd parameters employed in the present study. Besides, due to the balance between the volume and the curvature effect of the liquid droplet of Ni catalyst formed on the graphite substrate during CVD process, the shortest incubation time for SiC whisker nucleation was found for droplets of 2 um in diameter, instead of ith larger or smaller dimensions. 2002 Elsevier Science B v. All rights reserved. PACS:68.70;81.10.a:52.75r;81.10.Bk:8L.15Gh;81.10Aj Keywords: Al. Growth models: Al. Nucleation; A3. Chemical vapor deposition processes 1. Introduction tional applications, whisker and other fibrous forms of elemental and compound semiconductors With the increasing interest in the fabrication and ceramics have received considerable attention and characterization of one-dimensional crystal- [1-3]. Silicon carbide(SiC) whiskers as a kind of line materials for structural and potentially func- high strength fibrous material are commonly used as an effective reinforcing element for composite Corresponding author. Tel :+886-6-2757575: fax:+886-6 materials. As a response to the request from the 2380208 high-performance metallic and ceramic compo- E-mail address. icleu mail ncku.edu. tw (I.-C. Leu) sites, SiC whiskers as a reinforcing material have 0022-0248/02/S-see front matter c 2002 Elsevier Science B V. All rights reserved. PI:S0022-0248(01)02274-6Journal of Crystal Growth 236 (2002) 171–175 Nucleation behavior of silicon carbide whiskers grown by chemical vapor deposition Ing-Chi Leu*, Min-Hsiung Hon Department of Materials Science and Engineering, National Cheng Kung University, 1, Ta-Shueh Rd., Tainan 701, Taiwan Received16 October 2001; accepted28 November 2001 Communicatedby T. Hibiya Abstract Silicon carbide (SiC) whiskers as a kind of high strength fibrous material are commonly used as an effective reinforcing element for composite materials. The preparation andcharacterization of such high aspect ratio materials are of great importance to the understanding of fundamental properties and potential industrial applications of whisker materials. In this study the growth of SiC whiskers by chemical vapor deposition (CVD) from the thermal decomposition of methyltrichlorosilane was performed on Ni-coated graphite substrates in a hot wall reactor with an emphasis on the study of the fundamental nucleation and growth characteristics of the whiskers. Since vapor–liquid– solidmechanism is foundto be responsible for the growth of whiskers, the formation of the Ni catalyst andits subsequent evolution on whisker nucleation andgrowth is a subject of extensive research. Scanning electron microscope is employedto characterize the nucleation andgrowth of SiC whiskers. It is foundthat the incubation periodfor whisker nucleation and growth to noticeable dimension depends on the size of the Ni particles. It takes about 3 min for the first whisker to appear andabout 8 min to complete the whole nucleation stage for the case of Ni-coating thickness of about 2.5 mm under the CVD parameters employed in the present study. Besides, due to the balance between the volume and the curvature effect of the liquid droplet of Ni catalyst formed on the graphite substrate during CVD process, the shortest incubation time for SiC whisker nucleation was foundfor droplets of 2 mm in diameter, instead of those with larger or smaller dimensions. r 2002 Elsevier Science B.V. All rights reserved. PACS: 68.70; 81.10.a; 52.75.r; 81.10.Bk; 81.15.Gh; 81.10.Aj Keywords: A1. Growth models; A1. Nucleation; A3. Chemical vapor deposition processes 1. Introduction With the increasing interest in the fabrication andcharacterization of one-dimensional crystal￾line materials for structural andpotentially func￾tional applications, whisker andother fibrous forms of elemental andcompoundsemiconductors andceramics have receivedconsiderable attention [1–3]. Silicon carbide (SiC) whiskers as a kind of high strength fibrous material are commonly used as an effective reinforcing element for composite materials. As a response to the request from the high-performance metallic andceramic compo￾sites, SiC whiskers as a reinforcing material have *Corresponding author. Tel.: +886-6-2757575; fax: +886-6- 2380208. E-mail address: icleu@mail.ncku.edu.tw (I.-C. Leu). 0022-0248/02/$ - see front matter r 2002 Elsevier Science B.V. All rights reserved. PII: S 0022-0248(01)02274-6