Surface transfer doping of oxidised silicon-terminated (111) diamond using MoO₃

High-resolution core-level photoemission and Kelvin probe was used to examine surface transfer doping of oxidised silicon-terminated (111) diamond with the molecular acceptor MoO₃. A downward shift in the Fermi level position, relative to the diamond valence band maximum, commensurate with p-type surface doping was observed only for MoO₃ coverages in the range 0.2–0.6 ML and above. For lower MoO₃ coverages the appearance of distinct charge states of MoO₃ is ascribed to electron transfer from surface charge traps with an estimated density in the range 1–3 × 10¹³ cm⁻². Atomic force microscopy imaging suggests significant disorder of the surface compared to similarly prepared (100) diamond surfaces.