Deposition of transition metal carbides and superlattices using C60 as carbon source

Thin films of TiC, VC, and NbC have been deposited on MgO(001) by coevaporation of the metals and C-60 It was found that these metals induced a decomposition of the C-60 molecule and that carbide films can be formed at a temperature as low as 100 degrees C. Films deposited at this temperature were nanocrystalline and contained small amounts of amorphous carbon. Higher deposition temperatures resulted in epitaxial growth for TiC on MgO(001) at 250 degrees C, while NbC and VC required a temperature of 400-500 degrees C for epitaxial growth. The epitaxial relationship was found to be MeC(001)/MgO(001) and MeC[100]//MgO[100]. The best epitaxial films were obtained for TiC followed by VC and NbC. It is difficult to deposit epitaxial films within the whole homogeneity range. Attempts to deposit carbon-rich and/or stoichiometric films lead to the formation of free surface carbon and a subsequent loss of epitaxy. The coevaporation technique could also be used to deposit TiC/NbC superlattices at 500 degrees C. Attempts to form metastable carbides with Co failed and these films were found to contain a mixture of metallic Co and amorphous carbon. (C) 2000 The Electrochemical Society. S0013-4651(99)10-091-0. All rights reserved.