Within the arena of transparent conducting oxides (TCOs), indium tin oxide (ITO), an In_2O_3-rich compound of In_2O_3 and SnO_2, has long reigned supreme: it is inexpensive, easy to deposit as a thin film, offers 90 percent transmission at wavelengths longer than 350 nm, is compatible with standard fabrication processing and, last but by no means least, has excellent electrical properties. So, given all these attributes, surely ITO is a near ideal material for myriad applications. What could possibly be missing? Well, there is a fly in the ointment of this venerable oxide, along with that of most of its peers: a bandgap that quite simply comes up short for applications requiring a source of emission deep within the ultraviolet range - that is, wavelengths below 320 nm.
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