Activation of boron-dopant atoms in ion-implanted diamonds

Abstract

Different ratios of boron to carbon ions were implanted into diamond maintained at liquid-nitrogen temperature. After implantation, the diamonds were heated to 500 \ifmmode^\circ\else\textdegree\fi{}C by dropping them onto a platform situated in a vertical tube furnace, and then annealed for 1 h. This was followed by a further anneal at 1200 \ifmmode^\circ\else\textdegree\fi{}C in an argon atmosphere. It was found that under suitable conditions optical and electrical properties could be obtained which correlated with those found in natural semiconducting diamond. Thermally activated electrical conduction could, for instance, be established at an activation energy of \ensuremath{\sim}0.37 eV, which corresponds to the value measured for substitutional boron acceptors in diamond. Owing to the annealing cycle used, a relatively large amount of products resulting from radiation damage remained, which, in the carbon-ion-implanted diamond, manifested itself by increased optical absorption at short wavelengths. The results indicate that the product responsible for this absorption may be acting as a donor center situated at about 4 eV below the conduction band. Thermal electromotive-force measurements correlate with the movement of holes in the valence band.