Diamond surface conductivity experiments and photoelectron spectroscopy

A unique feature of diamond surfaces is a highly conductive p-type layer which is usually observed when the surfaces are hydrogen terminated. We present a combination of conductivity and photoelectron yield measurements on a variety of different diamond samples in order to elucidate the role of hydrogen and adsorbates for this phenomenon. The experiments show that hydrogen termination is a necessary but not a sufficient condition for the appearance of the surface conductivity. Additionally, adsorbates from the atmosphere are needed. On the basis of the experiments an electrochemical model is developed which can explain the effect of the hydrogen termination and also shows why hydrogen terminated diamond is the only semiconductor with p-type surface conductivity.