Cathodoluminescence experiments on isotopic clean diamond with carbon isotopes 12C and 13C

High-quality homoepitaxial diamond films grown by microwave plasma-assisted chemical vapor deposition from 12C, 13C and naturalC containing methane (CH4) gases have been studied by cathodoluminescence (CL) spectroscopy. Near-band-gap CL spectra at low temperatures were characterized in two isotopically enriched C diamond (12C, 13C) films. We observe an energy shift of the free-exciton recombination radiation with a change of the isotope composition from 12C to 13C. This result is in good agreement with both theoretical prediction as well as experimental results reported in the literature. In addition, strong excitonic emiss ion is detected from the isotopic clean 12C diamond films at 79 K.