Phase Changes in Transition Metal-Carbon Alloy Films (M-C; M=Fe, M, Co) Prepared by Co-Sputtering Deposition Technique

Transition metal-carbon alloy films, such as Fe-C, Co-C and Ni-C alloys, were prepared by a new type of co-sputtering deposition technique. Their phase changes caused by annealing were examined together with decomposition behavior. The formation ability and thermal stability of metastable phases, such as cobalt and nickel carbides, are explained by the difference in the fcffmation enthalpy for carbides. After annealing, graphite particles were always seen to grow around metal particles decomposed from carbides, probably due to the so-called metal-mediated nucleation and growth. Common features of the phase changes including decomposition behavior are also explained based on the same concept, partly taking account of subsequent dissociation of carbon from the carbides during annealing.