On the condensation and preferred orientation of TiC nanocrystals - effects of electric field, substrate temperature and second phase

The condensates formed by reacting Ti plasma with C2H2 gas (75 seem) under relatively low vacuum (1x10(-3) Torr) and collected on carbon-coated collod ion film were characterized by transmission electron microscopy to be TiC n anocrystals in random crystallographic orientation. The TIC condensates sho wed preferred orientation (200) when assembled on polycrystalline and amorp hous substrates at ca. 150 degrees C, and changed further into (111) when t he substrate was subject to voltage bias (-120 V) with or without preheatin g to 450 degrees C. The alpha-Ti co-deposited, with the TiC at a relatively low flow rate of C2H2 (25 seem), followed the crystallographic relationshi p: (0001)(alpha-Ti)//(111)(TiC); [11 (2) over bar 0](alpha-Ti)//[1 (1) over bar 0](TiC), in accordance with the TiC (111) preferred orientation. On th e other hand, the amorphous carbon formed at a high flow rate of C2H2 (250 seem) hindered the preferred orientation (111) of TiC. The effects of appli ed electric field, substrate temperature and second phase on the accumulati on and reorientation of the TiC condensates in the coating can be rationali zed by surface charge of the TiC crystallites, Brownian rotation-coalescenc e of the crystallites, and atom configuration specification at the interpha se interface, respectively. (C) 2000 Elsevier Science S.A. All rights reser ved.