The growth of thin PbO layers on lead films. II. Theory

Abstract

The lead oxidation data obtained in the experimental part of this paper were analyzed statistically and found to fit a rate law of the form, dX dt = α exp( X1 X). Using this dependence and certain known characteristics of orthorhombic PbO crystals, an oxidation mechanism is proposed which invokes the generation of oxygen vacancies at the Pb/PbO interface and their attentdant electric-field assisted transport across the oxide layer. This model seems to be consistent with the defect structure of PbO, and provides an explanation for the effects of temperature, oxygen pressure, lead microstructure and indium doping on the oxidation rate parameters, α and X. When combined with the observed thickness dependence of the oxide strain, the results suggests that the field required for the growth law arises from a piezoelectric potential present across the PbO layer. The α and X1 parameters show an expected interactive dependence upon one another, and the piezoelec-trically-coupled electric and mechanical forces control the oxidation rate. © 1973.