High carrier mobility in polycrystalline thin film diamond

Polycrystalline diamond films have been found to display p-type surface conductivity. No bulk impurity is added to the films; the p-type characteristics of the undoped diamond are thought to be due to a surface or near surface hydrogenated layer. Carrier concentrations within the range ${10}^{17}{\text{–10}}^{19}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{-3}}$ have been measured; control over the carrier concentration can be achieved by annealing the “as-grown” films in air. For a given annealing temperature a stable carrier concentration arises. The Hall carrier mobility has been explored and a value of $\text{>70\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{2}}\mathrm{/Vs}$ has been measured for a film with a carrier concentration of ${\text{∼5×10}}^{17}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{-3}},$ the highest reported for polycrystalline thin film diamond and equivalent to boron doped single crystal diamond.