Laser-scanning photoemission measurements of the silicon-silicon dioxide interface

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Abstract
We have used the uv line of the He–Cd laser at 3250 Å to excite photoemission of electrons from silicon into SiO2. A focused spot of light is scanned over the surface of the sample to determine lateral variations of the photocurrent. We compare data taken before and after a treatment that has caused positive ions to drift to the interface. Before the treatment, the photocurrent is uniform in magnitude over the surface. After the treatment there are very pronounced local peaks. The results from scanning photoemission are combined with measurements of C‐V characteristics, photovoltage, and the voltage dependence of photocurrent to obtain a fuller explanation of the effects of ion drift. Peaks in the photoemission current are sometimes, but not always, associated with a lower interface barrier. In some cases where the peaks are especially pronounced they coincide with the points of first breakdown on voltage stress.