What is it about?
Despite the fact that zinc oxide (ZnO) is a well-known transparent oxide, "black" ZnO has potential for photocatalytic applications. These black films are obtained by enhancing the oxygen deficiency up to 15% in ZnO thin films grown at 300 °C on c-cut sapphire single crystal substrates by pulsed electron beam deposition (PED). Furthermore, by a slight variation of the pressure in PED around 0.01 mbar, either transparent, stoichiometric and crystalline films or black, oxygen deficient and amorphous films can be obtained. PED is nothing more than an ablation film deposition method, in which a pulsed electron beam replaces the nanosecond pulsed laser.
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Why is it important?
Black and amorphous zinc oxide thin films with about 15% oxygen deficiency were obtained for the first time by PED, and their properties were compared to those of the transparent ones. Both films present a structural disorder (amorphous vs. polycrystalline) and a high density of carriers, leading to a temperature-dependent resistivity behavior specific to disordered metal-oxide systems. Black ZnO thin films exhibit enhanced absorption in the visible and near-infrared due to oxygen deficiency, extending the range of applications of zinc oxide thin films from transparent electronics to solar absorbers and photocatalysis.
Perspectives
It was a great pleasure to write this article, as it features co-authors with whom I have collaborated for a long time. At the same time, it was a challenge to experimentally demonstrate the role of oxygen deficiency in zinc oxide thin films, after having previously investigated this in indium oxide films. Indeed, oxygen deficiency can expand the range of thin film applications.
Dr. Magdalena Nistor
National Institute for Laser, Plasma and Radiation Physics (INFLPR)
Read the Original
This page is a summary of: From transparent to black amorphous zinc oxide thin films through oxygen deficiency control, Journal of Applied Physics, December 2022, American Institute of Physics,
DOI: 10.1063/5.0129135.
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