STRUCTURAL-CHANGES IN DOPED A-C-H FILMS DURING ANNEALING

The hardness of hydrogenated amorphous carbon (a-C:H) films is difficu lt to sustain at application temperatures above 400 degrees C. In this study, using Raman spectroscopy we examined the structural behaviour of Mo, Cu or N doped a-C:H films annealed at various temperatures up t o 800 degrees C. The intensity of the Raman disorder peak (D-peak) of graphite increased with increasing annealing temperature regardless of the type of dopant. In the case of pure a-C:H, the as-deposited film was mainly formed of random-network-type (RN-type) planar clusters alo ng with very small turbostratic-carbon-type (TC-type) clusters. When a nnealed, the RN-type clusters transformed gradually into very small TC -type clusters while already existing TC-type clusters grew to larger sizes. When 0.6 at.% Mo was integrated into a-C:H in a multilayer fash ion, a very small amount of TC-type clusters formed in as-deposited fi lms. When annealed, Mo in the multilayer structure was found to be ben eficial for retaining smaller TC-type clusters. Mo and Cu, when incorp orated by a codeposition method, lowered the temperature of formation of relatively larger TC-type clusters, similar to the effect of nitrog en.