Surface Electrical Changes Caused by the Adsorption of Hydrogen and Oxygen on Silicon

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Abstract
Measurements of conductance, lifetime, change in contact potential with light, and contact potential have been carried out on bombardment‐cleaned siliconsurfaces and during the adsorption of molecular oxygen and atomic hydrogen. In the case of oxygen adsorption, the work function increased linearly with coverage. A change of 0.35 ev was obtained in going from θ=0 to θ=1. Very small changes in the transport properties were observed. Hydrogen atoms produced an initial decrease in work function of 0.1 ev for coverages below θ=0.35. From θ=0.35 to θ=1.0 the work function was increased by 0.3 ev. The changes in the transport properties were substantial and indicated a downward movement of the energy bands at the surface by about 0.08 ev. In the clean condition, the valence band edge was 0.12–0.14 ev below the Fermi level at the surface compared to 0.36 ev in the interior. The effect of hydrogen adsorption is discussed in terms of the adsorption data previously obtained on this system.