Modeling of transmittance, reflectance and scattering of rough polycrystalline CVD diamond layers in application to the determination of optical constants

Abstract

The optical constants of CVD diamond layers on silicon substrates have been determined from spectrophotometric measurements. The rough surface of polycrystalline diamond layers causes scatter losses, which reduce the specular transmittance and reflectance of the layers. A model is derived to consider the effects of surface roughness in terms of surface scattering and coherence disturbance. Both effects can be described by means of a single parameter — the root mean square (rms) roughness. The model has proved useful to fit the experimental spectra. The optical and geometrical parameters obtained from the fit are in good agreement with the results of additional measurements, such as SEM, mass density determination. Raman spectroscopy and direct measurements of the position of the band gap of the samples.