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 collodion film were characterized by transmission electron microscopy to be TiC nanocrystals in random crystallographic orientation. The TIC condensates showed preferred orientation (200) when assembled on polycrystalline and amorphous substrates at ca. 150 degrees C, and changed further into (111) when the substrate was subject to voltage bias (-120 V) with or without preheating 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 relationship: (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 the 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 applied electric field, substrate temperature and second phase on the accumulation and reorientation of the TiC condensates in the coating can be rationalized by surface charge of the TiC crystallites, Brownian rotation-coalescence of the crystallites, and atom configuration specification at the interphase interface, respectively. (C) 2000 Elsevier Science S.A. All rights reserved.