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 °C and 1100 °C. Fluences under investigation range from 4.5 to 6.2 x 10¹⁷ Si cm^-2 . This implantation scheme yields a buried layer rich of epitaxial 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 can not 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^-3and mobilities higher than 2 cm²/Vs. 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.