Copper Oxides (Cu2O, CuO)

Publisher Summary Cuprous oxide (Cu 2 O) is a semiconductor with a direct band gap of 2.17 eV. It has been the object of several basic studies concerning optical-band-gap absorption, its temperature dependence, and the interpretation of the low-temperature absorption line spectrum below the gap as transitions to excitonic levels. The partly ionic character of the bonding causes structures in the optical functions in the infrared spectral region. Black cupric oxide (CuO) is also a semiconductor, obviously with a smaller optical band gap than the red oxide. This chapter highlights the technical applications of copper oxides. Oxidizing copper is one of the alternatives in preparing the selectively absorbing surface of a thermal solar collector. In this application, the black oxide results in higher efficiency owing to its higher absorption of solar radiation. The ease with which oxidation of copper can take place is partly a corrosion problem, but it is also one of the reasons for the technical interest in this system. The chapter reviews the published optical constants for the cuprous and cupric oxides in the visible and near-infrared spectral regions.