Synthesis of diamond thin films through a transformation of a catalytically produced diamond precursor phase

Abstract

Amorphous carbon (a-C:H) films were formed on Cu substrates using a carbide-forming transition metal (Mo, Ta or W) as a catalyst with hot-filament chemical vapour deposition (CVD). This amorphous carbon was transformed into diamond in less than one minute when heated at 1273 K with the hot filaments in a H 2-0.3%CH 4 atmosphere. During the heating etching and transformation took place simultaneously causing a thinning of the film. After the transformation, the film became transparent and insulating. Scanning electron micrographs of the precursor film and the film after the transformation were taken. Raman spectra of the precursor phase was similar to the reported spectra of a-C:H. Raman spectra of the transformed film, however, showed a distinct diamond peak at a wavenumber of 1331±2 cm −1 (FWHM≤10 cm −1). Continuous diamond films with a thickness of less than 1 μm were also grown using the same catalysts in approximately 4.5 h. It was proposed that precursor diamond particles formed at the catalytic surface-Cu boundary and diffused to the Cu surface where they were exposed to atomic hydrogen and then transformed into diamond.