Characterization of < 111 > diamond thin films by micro-Raman spectroscopy

Abstract

High-resolution confocal micro-Raman spectra show that for homoepitaxial growth on <111>-oriented surfaces the zone-center phonon peak of the epilayers may occur a few cm(-1) below the peak of the relaxed diamond. This indicates a strong tensile strain in the films, while close to the interface the substrate is under compression. This effect was observed in both phosphorus-doped and undoped epilayers, as well as on some facets of a polycrystalline sample. Results obtained on <111>-oriented films grown by microwave plasma chemical vapor deposition in three different laboratories are compared, providing some hints as to how such undesirable strain effects can be avoided. (C) 2003 Elsevier B.V. All rights reserved.