A positron annihilation study on the defect properties of doped diamond films

Doppler broadening measurements were performed on undoped, boron doped, and sulfur doped diamond films. The defect properties in these different diamond films were analyzed and the effect of boron concentration in the B-doped diamond films on these properties was studied. The Doppler broadening measurements were characterized with the shape parameter S and the wing parameter W. From these fitted characteristic S and W values of the diamond films and plots of S vs. position implantation energy, it was deduced that undoped and S-doped diamond films are rich of vacancy-like defects, while B-doped diamond films are poor of vacancy-like defects. This difference may originate from possible different charge state of the vacancy-like defects and from the incorporation of impurities in the different growth ambient of the films. By comparing the parameters obtained in the Doppler broadening measurements of diamond films with different boron concentration, we found that S values of B-doped diamond did not decreased with the increasing of boron concentration, which suggests that more damaged regions form in the higher boron concentration samples.