Spectroellipsometry characterization of optical quality vapor-deposited diamond thin films

Abstract

Quantitative characterizational methods are required to optimize vapor-deposited diamond thin films for optical applications. In this work, spectroellipsometry has been applied to deduce two important characteristics of diamond films: the volume fraction of sp2-bonded defects in the bulk and the thickness of the roughness layer on the surface. We have determined these characteristics versus substrate temperature and CH4:H2 flow ratio for optical quality films prepared to 1000–4000 Å by microwave plasma-assisted chemical vapor deposition. Under optimum conditions, uniform films with ∼100 Å roughness and 3 vol.% bulk sp2C are obtained.