Scanning tunneling spectroscopy of lead sulfide quantum wells fabricated by atomic layerdeposition

Abstract

We report the use of scanning tunneling spectroscopy (STS) to investigate one-dimensionalquantum confinement effects in lead sulfide (PbS) thin films. Specifically, quantumconfinement effects on the band gap of PbS quantum wells were explored by controlling thePbS film thickness and potential barrier height. PbS quantum well structures with athickness range of 1–20 nm were fabricated by atomic layer deposition (ALD). Two barriermaterials were selected based on barrier height: aluminum oxide as a high barrier materialand zinc oxide as a low barrier material. Band gap measurements were carried out bySTS, and an effective mass theory was developed to compare the experimentalresults. Our results show that the band gap of PbS thin films increased as thefilm thickness decreased, and the barrier height increased from 0.45 to 2.19 eV.