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Title:Surface states on the cleaved (III) silicon surface
Author(s):Aspnes, David Erik
Doctoral Committee Chair(s):Handler, Paul
Department / Program:Physics
Subject(s):single crystal silicon
conductivity changes
silicon III
Fermi level
valence band edge
Abstract:Conducti vi ty changes resulting when sing.le crystal silicon is cleaved in ultrahigh vacuum have been measured parallel to the cleavage plane over various temperature ranges for gold dope~ and high.resistivity boron doped silicon. The resulting change of conductivity is related to the difference between the valence band edge and the Fermi level in the bulk and at the surface, and to the quantity of charge in the surface states which has been trapped from the bulk. Analysis of the data shows a high density of surface states on the clean cleaved surface, centered 0.28 ± 0.08 eV above the valence band edge. The den- 13 -2 -1 sity~depends on the model chosen, but is at least 10 cm eV • Results obtained in this experiment are correlated with results obtained by other experiments. Oxygen absorption is observed to introduce different surface states, also of high density but centered 0.6 + 0.15 eV above the valence band edge of the surface. Low temperature measurements on gold doped silicon crystals show that probably no conduction takes place through the surface states themselves, either on clean or oxidized surfaces. These results are used to obtain possible models of the surface state distributions. A two dimensional conformal mapping is used to derive relations between conductance change and conductivity per square for several geometries, and to obtain corrections to the observed conductance change f.or cleavage planes not parallel to the initial current flow lines.
Issue Date:1965
Genre:Dissertation / Thesis
Rights Information:1965 David Erik Aspnes
Date Available in IDEALS:2011-05-19
Identifier in Online Catalog:6133945

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