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 IIa) diamonds. They have been implanted with ${\mathrm{O}}^{+},$ ${\mathrm{C}}^{+}$ and $\left({\mathrm{B}}^{+}{+\mathrm{C}}^{+}\right)$ 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 ${\mathrm{O}}^{+}$- and $\left({\mathrm{B}}^{+}{+\mathrm{C}}^{+}\right)$-implanted layers. After implantation at liquid-nitrogen target temperature, the diamonds were rapidly heated to 500 °C and maintained there for 30 min. Electrical measurements showed that the ${\mathrm{O}}^{+}$ and $\left({\mathrm{B}}^{+}{+\mathrm{C}}^{+}\right)$ diamonds conducted orders of magnitude better than the ${\mathrm{C}}^{+}$-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 ${\mathrm{O}}^{+}$ implantation steps to lower the resistance further, Hall-effect measurements confirmed that this diamond became n-type conducting.