Characterization of ‹111› diamond thin films by micro-Raman spectroscopy
Résumé
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.