Cathodoluminescence of boron-doped heteroepitaxial diamond films on platinum

Cathodoluminescence (CL) spectra of diamond films epitaxially grown on single crystal platinum (111) have been investigated at room temperature and 89 K. It was found that the CL spectra of the heavily boron-doped (> 3 × 1020 cm-3) diamond films of more than 16 μm thickness consist only of a near-edge emission at 248±1 nm (5.00±0.02 eV), while any other emissions are absent. It was also found that the temperature dependence of the 248 nm band is very unusual, since its intensity increases as temperature increases. This result is in strong contrast to CL intensities of both the free exciton and the bound exciton, which decrease significantly with temperature. It is concluded that a new electronic band due to heavily-doped boron is the origin of the 248 nm emission.