The role of hydrogen plasma power on surface roughness and carrier transport in transfer-doped H-diamond

Surface transfer doping of diamond fundamentally requires termination of the diamond surface with a species such as hydrogen to allow the interfacial charge exchange required to establish surface conductivity. Here we show the effects of varied hydrogen plasma power on the roughness and conductivity of the (100) diamond surface. Prior to hydrogen termination, substrates were etched using tailored Cl2 + Ar and O2 + Ar chemistries to produce a very smooth surface of ~0.2 nm roughness average while also removing ~3.4 μm from the top surface as measured by Atomic Force Microscopy (AFM). Use of etching post polishing provides an effective means of producing smoother diamond surfaces with reduced crystal damage as opposed to scaife polishing alone. By producing nominally identical etched surfaces, a relationship between surface conductivity and hydrogen termination plasma power was observed. Using MoO3 as a surface acceptor material, Hall measurements were performed to examine sheet resistance, carrier density and mobility within the diamond. Increased surface conductivity due to enhanced hole mobility was observed at higher hydrogen plasma power conditions, despite an associated increase in roughness of the diamond surface.