Structural and chemical phase transitions in tungsten carbide films evidenced by the analysis of their stiffness tensors

Brillouin light scattering (BLS) is used to provide a comprehensive study of thin tungsten carbide films deposited on single crystal silicon substrates whose distinctive nature depends critically on the deposition parameters. The use of stepped films in these slow-on-fast systems provides enhanced data sets and allows the velocity dispersion of the observed surface excitations, including the discrete Rayleigh and Sezawa modes to be studied in detail. Comprehensive and powerful methods of data analysis and interpretation including the recently developed Monte Carlo (MC) method, the surface Green’s function, and classical approaches are applied to extract the effective elastic constants and density of each of the films. The MC and Green’s function methods are used to remove ambiguities in Sezawa mode assignments and to identify a mode-crossing event. Auger electron spectroscopy and x-ray diffraction investigations confirm conclusions about chemical composition and microstructure obtained by BLS including a ...