The transient-current technique was used as a sensitive method for detecting small concentrations of charged defects in diamond and to study its photo-ionization spectrum. It was found that ionized impurity concentrations in the range of 109 to 1013/cm3 could be easily detected in diamond. By continuously measuring the charge concentration, while illuminating the samples with monochromatic light, the evolution of the charge state of the dominating defect could be continuously monitored. The photo-ionization cross-section spectrum was obtained from the dominant deep defect in single-crystalline chemical vapor deposited diamond by using this method. The photo-ionization spectrum exhibited an onset at photon energies above 2.2eV. It was also found that the defect was in the positively charged state and acted as an electron trap. The observed spectrum could be attributed to the single substitutional N impurity.

Photoionization Measurement of Deep Defects in Single-Crystalline CVD Diamond Using the Transient-Current Technique. J.Isberg, A.Tajani, D.J.Twitchen: Physical Review B, 2006, 73[24], 245207 (4pp)