Negative electron affinity effects on H plasma exposed diamond (100) surfaces

The effects of annealing and a H plasma exposure on natural type IIb diamond (100) were investigated by means of ultraviolet photoemission spectroscopy (UPS). The diamond (100) surface was found to exhibit a negative electron affinity (NEA) following a 900 °C anneal in ultrahigh vacuum. After a H plasma exposure the NEA peak in the UPS spectra had doubled in height. An anneal to 1100 °C resulted in the removal of the sharp NEA feature. A second H plasma treatment resulted in the reappearance of the NEA peak like after the first H plasma exposure. A 2 × 1 reconstructed low-energy electron diffraction (LEED) pattern was observed subsequent to the anneals as well as the H plasma treatments. The fact that a NEA can be induced or removed repeatedly by means of a H plasma exposure or a 1100 °C anneal respectively provides evidence to correlate the appearance of a NEA with the presence of a monohydride terminated surface.