High carrier mobilities in black diamond
Hydrogen plasma treatment of diamond renders the surface p-type, with the carriers emerging with little thermal activation, in sharp contrast to the use of boron for the formation of p-type material. To date, it has been thought that only the highest quality 'white' polycrystalline material is useful for electronic device applications, with many regarding single-crystal diamond as ultimately the substrate material of choice. In this paper it is shown that when p-type material is produced through hydrogenation, this is not the case. 'Black' polycrystalline diamond, which can be grown much more rapidly than white, shows carrier concentrations and mobility values similar to both white polycrystalline diamond and single-crystal material. This result has important implications for the provision of low-cost black-diamond substrates for device applications.