Scanning tunneling microscopy and spectroscopy of non-doped, hydrogen terminated CVD diamond

The electron emission from a diamond surface is influenced by the surface termination and the surface density of states. It is known that the hydrogen termination of diamond surfaces induces p-type conduction. Scanning tunneling spectroscopy (STS), combined with high-resolution topographical imaging with the scanning tunneling microscope (STM), enables to investigate local variations in the electronic structure of surfaces. We show that the hydrogen termination is sufficient to obtain reproducible STM and STS measurements. We find that the formation of a Schottky point contact between tip and sample gives rise to a rectifying I-V characteristic. Retracting the tip results in a change in the I-V characteristics from a rectifying behavior towards normal tunneling behavior. The tunneling measurements confirm the surface p-type conductivity and Fermi level pinning at the valence band.