n-type conductivity in high-fluence Si-implanted diamond.

Epitaxial SiC nanocrystals are fabricated by high-fluence Si implantation into natural diamond at elevated temperatures between 760 and 1100 °C. Fluences under investigation range from 4.5 to 6.2×1017 Si cm-2. This implantation scheme yields a buried layer rich of epitaxially aligned SiC nanocrystals within slightly damaged diamond. The generation of a small fraction of graphitic sp2 bonds of up to 15% in the diamond host matrix cannot be avoided. Unintentional coimplantation with nitrogen results in a very high doping level of more than 1021 cm-3. Resistivity and Hall measurements in van der Pauw geometry reveal a high, thermally stable n-type conductivity with electron concentrations exceeding 1020 cm-3 and mobilities higher than 2 cm2 /V s. It is supposed that both the SiC regions as well as the diamond matrix exhibit n-type conductivity and that the electron transport occurs across the low-resistivity SiC nanograins. In the SiC nanocrystals the electrons originate from nitrogen donors whereas in diamond defects are responsible for the electron conductivity. The formation of disordered graphite, which leads to low electron mobility, is substantially reduced by the SiC formation. [ABSTRACT FROM AUTHOR]