Raman-based measurements of optical properties of thin solid films: application to amorphous diamond

The potentialities of Raman spectroscopy to measure optical properties of thin solid films are considered. A new approach based on the analysis of interference-induced modification of the Raman scattering from the substrate material together with the normal reflection coefficient is proposed. It is shown that the method provides the absorption coefficient and refractive index of the film bulk with high spatial resolution and accuracy, and it can be applied to various transparent thin films. The developed approach is used to measure optical properties of amorphous diamond films deposited onto crystalline silicon. In the case of the amorphous diamond films deposited with a mass-separated ion beam, a straightforward correlation between the absorption coefficient and Raman spectra is obtained, which can be also used to estimate the optical properties. For the films deposited with pulsed cathodic are discharge, such a relation appears to be more complex, which possibly indicates extensive variations of the sp(2) clusterization in the latter deposition method. (C) 1998 Elsevier Science S.A. All rights reserved.