Raman characterization of amorphous carbon films

Amorphous carbon films, deposited with the LASER-ARC technique, have been characterized using Raman scattering experiments at an excitation wavelength of 633 nm provided by a He-Ne laser. To distinguish between the homogeneous amorphous film and incorporated particles area resolved measurements have been carried out due to the laser spot diameter of 1 m. Typical diamondlike (DLC) films, grown near room temperature, show a broad Raman band between 1000 cm^–1 and 1800 cm^–1 fitted very well by two gaussian distributions. Films deposited at higher substrate temperatures reveal more graphitic features in the spectra. The spectra of particles consists of a graphite-like portion originated from the graphitic structure of the particle and a diamond-like portion caused by the covering DLC film. The degree of disorder and diamond-likeness in the film structure is quantified by the peak position, the full width at half maximum (FWHM) and intensity relation of the fitted D- and G-peaks.     

Visualization of surface elastic waves on structural materials

A technique developed by Adler, Korpel, and Desmares for the visualization of surface elastic waves has been applied to the problem of inspecting structural materials. The technique produces a stationary display of the crests and troughs of a travelling surface wave, much as would occur under stroboscopic illumination. Changes in the local elastic properties on or near the surface are indicated by scattering and distortion of the wavefronts. Photographs are presented illustrating the use of the technique both in locating defects and in studying the intrinsic properties of materials. The examples include thickness variations and holes in sheets and plates, cracks in surfaces, and metallurgical variations in nominally defect-free material.