Brillouin light scattering on diamond and diamondlike carbon coatings

Brillouin light scattering is a well-established technique for measuring sound velocities and therefore elastic constants. Previous publications showed that a dispersion measurement of the surface (Rayleigh) modes for amorphous carbon films yields information about thickness, mass density, and shear modulus of the films. Due to the transparency of diamond crystals one longitudinal and two transverse acoustic bulk phonons were observed from which the elastic constants cll, cl2 and c44 respectively, were determined exhibiting the characteristic values of natural diamond. We report in this paper Brillouin light scattering on carbon films of different crystallographic phases, i.e. on chemical vapour deposited (CVD) polycrystalline diamond, polycrystalline graphite with texural structure, and amorphous carbon films (a-C:H) which were prepared under different conditions. For example, the a-C:H films were treated after deposition by ion implantation and annealing at various doses and temperat ures, respectively. From the measured sound velocities of the acoustic phonons Young's modulus, shear modulus, and bulk modulus of the films were calculated as functions of the preparation conditions. On a-C:H films the depth-sensing indentation tests were also performed. The values of ultramicrohardness of these films are, therefore, also reported.