Formation of shallow acceptor states in the surface region of thin film diamond

Considerable interest exists in fabrication of electronic devices from thin film polycrystalline diamond. To date, doping this material to achieve good free carrier concentrations and mobilities at room temperature has proved difficult. In this letter we report low temperature Hall effect measurements made on diamond films subjected to a hydrogenation process, such that the near surface region becomes p type without the addition of conventional dopant atoms. High carrier concentrations and mobilities can be achieved. The change in carrier concentration within the temperature range 10–300 K does not change as expected for most films, actually increasing as the temperature falls. This effect could be related to the confinement of carriers at the surface caused by the dipole provoked by adsorbed hydrogen on the diamond. However, polished films display more conventional behavior in that the carrier concentration falls with falling temperature.