DEFECT PHOTOLUMINESCENCE IN POLYCRYSTALLINE DIAMOND FILMS GROWN BY ARC-JET CHEMICAL-VAPOR-DEPOSITION

We have studied a series of sharp photoluminescence emission lines bet ween 1.65 and 1.80 eV in synthetic diamond films. The series of lines is decomposed into a set of parent lines plus vibrational sidebands sp aced 24 meV apart. This energy does not correspond to any phonons with high density of states in the diamond crystal. The relative intensiti es of the main lines exhibit no temperature dependence (between 20 and 160 Ii), implying ground-state splitting. The narrow linewidth and te mperature-independent emission energy imply only weak interaction with the diamond host The temperature-dependence of the linewidth is well described by thermal broadening. We attribute the emission to optical centers as a consequence of tungsten incorporation into the diamond fi lm. The tungsten originates from the electrode during deposition.