Monitoring laser-induced microstructural changes of thin film hydrogenatedamorphous carbon (a-C : H) using Raman spectroscopy

Thin films (10 - 150 nm) of a-C:H on glass and silicon substrates have been studied utilizing a confocal micro Raman system using an argon ion laser ( 514.5 nm) and helium-neon (He-Ne) laser (637.8 nm) for sample excitation. T he relationship between the measured Raman spectrum and the film thickness, substrate material, laser intensity and exposure time, have been assessed. From this, the dominant variables have been identified. Microstructural ch anges in the form of the growth of graphitic crystallites, similar to that of thermally annealed samples, have been observed. For longer laser irradia tion exposure times this graphitic component decreases, revealing an amorph ous carbon structure, possibly containing some tt tetrahedrally-bonded carb on. Optical microscopy and topographical atomic force microscopy also highl ight the range of laser ablated conditions that result. (C) 1998 Elsevier S cience S.A. All rights reserved.