Optical properties of microcrystalline zinc oxide. Influence of defects produced by interaction with carbon monoxide

Abstract

Infrared transmission spectra and ultraviolet–visible–near-infrared diffuse reflectance spectra are reported for microcrystalline ZnO samples in contact with CO at different temperatures. The absorptions observed after interaction at 300 K are ascribed to the formation of oxidized chemisorbed CO and surface point defects on ZnO. Interaction at 473 K produces extensive reduction of the ZnO and the population of the conduction band, and phonon–plasmon coupling is observed. After cooling at 300 K, electrons from the conduction band populate bulk defects.