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)-10(19) cm(-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 >70 cm(2)/Vs has been measured for a film with a carrier concentration of similar to 5 x 10(17) cm(-3), the highest reported for polycrystalline thin film diamond and equivalent to boron doped single crystal diamond. (C) 1998 American Institute of Physics.