LASER-INDUCED SURFACE-STRUCTURES ON DIAMOND FILMS

Periodic ripples are observed to develop at the surface of faceted chemical vapor deposited diamond films during laser irradiation at an angle of incidence beyond a critical value. The grating pattern perpetuates itself across the surface upon irradiation with subsequent, overlapping pulses. The ripples have spacings of typically 10 mu m, and are oriented parallel to the plane of incidence, irrespective of the laser wavelength or the polarization. Neither diffraction nor interference effects can therefore be the cause for the rippling. Rather, a shadowing effect appears to initiate the corrugation. The occurrence of permanent ripples poses a limit to the laser polishing of rugged diamond films. However, rippling is avoided and significantly smoother films result (with an average roughness of 33 nm compared to about 100 nm) by rotation of the diamond film during laser processing. (C) 1995 American Institute of Physics.