9.3: Sub-bandgap photoemission correlated with adsorbed molecules and bulk impurities in diamond

We report on photoemission images from NEA diamond using sub-bandgap and near-bandgap photon energies. Emission can be stimulated with photon wavelengths as low as 365 nm, but the low-energy emission disappears after heating the diamond to 700°C, while emission stimulated with 254 and 224 nm photons remains. In both cases the emission occurs only where the concentration of bulk point defects is low. We explain this behavior as the result of photon absorption both in the bulk and at the surface competing with bulk recombination.