n-type semiconducting diamond by means of oxygen-ion implantation

By a judicious choice of implantation and annealing conditions, an n-type conducting layer with activation energy of about 0.32 eV has been created in oxygen-implanted diamond. This conclusion was reached as a result of performing three similar implantations in identical, high-purity (type Ila) diamonds. They have been implanted with O+, C+ and (B++C+) ions to respectively create the same density and distribution of radiation damage in each diamond. The density and distribution of dopant atoms were the same for the O+- and (B++C+)-implanted layers. After implantation at liquid-nitrogen target temperature, the diamonds were rapidly heated to 500 degrees C and maintained there for 30 min. Electrical measurements showed that the OC and (B++C+) diamonds conducted orders of magnitude better than the C+-implanted diamond. Thermal-emf measurements were used to determine n- and p-type conduction. The resistance behavior was in both cases commensurate with that of a highly compensated, extrinsic semiconductor. After more O+ implantation steps to lower the resistance further, Hall-effect measurements confirmed that this diamond became it-type conducting.