Relation between the dislocations in chemically vapour-deposited diamond and the linewidth of the Raman spectrum

Abstract

The 13C epitaxial diamond thin films were grown on the (100) planes of synthesized 12C type IIb diamond substrates by electron-assisted chemical vapour deposition. A chemical etching pre-treatment was performed on the substrate to clean the surface. The etchant used consisted of potassium nitrate and potassium chloride. The reactant gas used was a 1% 13C isotope CH 4H 2 mixture gas in order to distinguish between the Raman spectra of the 13C epitaxial film and the 12C diamond substrate. Epitaxial growth of thin films was confirmed by reflection high energy electron diffraction patterns. Etch pits related to dislocations were observed with Nomarski optical microscopy and the use of wet etching. A relation between the etch pit density and the first-order Raman spectrum of the epitaxial CVD diamond was found. When the etch pit density increased from 9.8 × 10 4 to 4.7 × 10 5 cm −2, the full width at half-maximum of the first-order Raman spectrum broadened from 4.9 to 6.6 cm −1. At the same time, the peak wavenumber of the Raman spectra increased from 1284.3 to 1286.8 cm −1. The slit width was 1.2 cm −1.