Coincidence Doppler broadening studies were carried out on CVD diamond films. The coincidence Doppler broadened spectra were analyzed to obtain information about the chemical surroundings at the annihilation site. Remarkably large fraction of positrons were seen to annihilate with the N present as impurity in low concentration. Complementary positron lifetime measurements indicated saturation trapping of positrons, primarily in monovacancies and vacancy clusters. The information obtained from coincidence Doppler broadening and complementary positron lifetime studies provides direct observation of N decorated vacancies or N vacancy complexes in diamond films. The results highlighted the potential of the coincidence Doppler broadening technique for characterizing impurity precipitates and impurity vacancy complexes in diamond.

Identification of Nitrogen Decorated Vacancies in CVD Diamond Films using Positron Annihilation Coincidence Doppler Broadening Spectroscopy. A.Sachdeva, K.Sudarshan, P.K.Pujari, Goswami, K.Sreejith, V.C.George, C.G.S.Pillai, A.K.Dua: Diamond and Related Materials, 2004, 13[9], 1719-24