ION-IMPLANTED N-TYPE DIAMOND - ELECTRICAL EVIDENCE

High-purity (natural type IIa) diamonds were treated by the cold implantation rapid annealing (CIRA) process using extremely low dose (about 10(4) times lower than usual), and damage-equivalent, carbon, boron and phosphorus ion implantations. The electrical properties of the carbon implanted (C+-CIRA treated) diamond did not change significantly from its virgin condition. In contrast, both the B+-CIRA and P+-CIRA diamonds showed different electrical behaviour, which could thus only be ascribed to the presence of the boron and phosphorus atoms respectively. Thermoelectric (hot probe) measurements showed the B+-CIRA diamond layer to be p-type (as expected) and the P+-CIRA layer to be n-type. Difficulties were experienced in effecting ohmic contacts to the P+-CIRA diamond, and the results indicate that for the latter treatment to lead to semiconductor-quality material, the diamond substrate must be substantially free from strain and contain a low density of intrinsic defects.