Tunneling relaxation of photocurrent from passive films on stainless steel

Abstract

The photocurrent transient effects of passive films grown on austenitic stainless steels in borate solutions have been investigated and explained by extending a mid-bandgap states model that was previously developed for titanium oxide. Tunneling of electrons trapped in mid-bandgap states into the conduction band was proposed as the reason behind the slow relaxation of photocurrent once the light is turned off. In addition, it was found that surface recombination effects started to appear at potentials where Cr(III) is expected to occur in the passive film, supporting earlier suggestions that this species can act as recombination centers. © 2006 The Electrochemical Society. All rights reserved.