Properties of a new, low bandgap photoconducting phase of lead oxide

Abstract

Atomic sputtering has been employed to fabricate a new, thin ( ⩽ 900 nm) n-type semiconducting phase of lead oxide of approximate stoichiometry PbO 1.50. Films 120 to 880 nm in thickness deposited in a 100% O 2 plasma and vacuum annealed for 8 h reproducibly exhibited indirect bandgaps of ~1.18 eV, while films of ~ 320 nm and vacuum annealed for ~1 h displayed higher bandgaps of ~1.30 eV. Films deposited in a 50:50 mixture of O 2 and N 2 resulted in an oxide displaying a bandgap of ~1.44 eV. All films thicker than 400 nm required vacuum annealing at ~ 250° C for periods of time > 2 h before any photoelectrochemical response was observed. The lower bandgap oxide phases are stable in aqueous alkaline media over a narrow potential range of ~ 0.20 V both in the dark as well as under chopped white light illumination (~ 200 mW/cm 2). These films have been characterized using a variety of techniques including XPS, Auger, X-ray diffraction, impedance and photoelectrochemical spectroscopies.