HIGH CARRIER MOBILITY IN POLYCRYSTALLINE THIN-FILM DIAMOND

Polycrystalline diamond films have been found to display p-type surfac e conductivity. No bulk impurity is added to the films; the p-type cha racteristics 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 carri er concentration can be achieved by annealing the ''as-grown'' films i n air. For a given annealing temperature a stable carrier concentratio n 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 polycrystall ine thin film diamond and equivalent to boron doped single crystal dia mond. (C) 1998 American Institute of Physics.