Deposition of transition metal carbides and superlattices using C-60 as carbon source

Thin films of TiC, VC, and NbC have been deposited on MgO(001) by coevapora tion of the metals and C-60 It was found that these metals induced a decomp osition of the C-60 molecule and that carbide films can be formed at a temp erature as low as 100 degrees C. Films deposited at this temperature were n anocrystalline and contained small amounts of amorphous carbon. Higher depo sition 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 fo r 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 Ti C followed by VC and NbC. It is difficult to deposit epitaxial films within the whole homogeneity range. Attempts to deposit carbon-rich and/or stoich iometric films lead to the formation of free surface carbon and a subsequen t loss of epitaxy. The coevaporation technique could also be used to deposi t TiC/NbC superlattices at 500 degrees C. Attempts to form metastable carbi des with Co failed and these films were found to contain a mixture of metal lic Co and amorphous carbon. (C) 2000 The Electrochemical Society. S0013-46 51(99)10-091-0. All rights reserved.