It has been known for some time that hydrogen within the bulk of diamond in
creases the conductivity of the material. However, only recently did it bec
ome apparent that the surface of thin film diamond can display p-type condu
ctivity and that this too related to the presence of hydrogen. The origin o
f this effect has been controversial. We have used a wide range of techniqu
es to study hydrogenated polycrystalline CVD diamond films to solve this pr
oblem. The generation of near surface carriers by hydrogen, which resides w
ithin the top 20 nm of 'as-grown' CVD films, is the origin of the conductiv
ity rather than surface band bending which had also been proposed. Up to 10
(19) holes cm(-3) can be measured and mobilities as high as 70 cm(2)/Vs rec
orded. H-termination of the surface is important for the formation of high
quality metal-diamond interfaces. (C) 1999 Elsevier Science Ltd. All rights
reserved.