Isochronal annealing of the electrical properties of electron-irradiated semiconducting diamond

Two semiconducting diamonds were irradiated with 1 Mev electrons. The specimen temperature during the irradiation was 77°K and the cumulative dose was of the order of 8 μAhr/cm2. The resistivity ρ and the Hall coefficient R were measured at ambient temperature before the irradiation, at half the cumulative dose and at the end of the irradiation. The specimens were subsequently subjected to a series of isochronal heatings at successively increasing temperatures in the range 200 to 1200°c. Each heating lasted for 30 min. ρ and R were measured at ambient temperature after each heating. From these measurements the concentration NR , of radiation-induced donor levels and the mobility μH of the charge carriers (positive holes) were calculated. NR was found to increase approximately linearly with the dose D. This is consistent with the radiation-induced donor centres being vacancies or carbon interstitials. μH decreased with D, presumably largely due to an increase in ionized centre scattering. Both NR and μH exhibited reverse annealing, i.e. annealing producing changes in the same direction as the radiation damage. Reverse annealing in both specimens was first observed after heating at 400°c. The behaviour of NR on annealing was not found to correlate with that of μH in either specimen. However, the qualitative behaviour of NR was identical in both specimens. The same applies to the behaviour of μ H. The values of NR after heating at 1200°c were equal to those before irradiation in both specimens. The value of μH after heating at 1200°c was higher than that before irradiation for one specimen and approximately equal to that before irradiation for the other specimen. We wish to thank Professor P. T. Wedepohl for a critical reading of the manuscript and Drs. H. B. Dyer and F. A. Raal of Industrial Distributors (1946) Limited for permission to publish this paper.