Transparent conducting oxides (TCOs), with high optical transparency and excellent electrical conductivities, form a group of technologically important materials For example, indium tin oxide (ITO) thin films are widely used as transparent electrodes in optoelectronic devices for visible wavelengths. It is well-known, however, that ITO thin films exhibit high reflectance and strong absorption in the terahertz (THz) frequency range. Recently, ITO nanomaterials have attracted a lot of attention, because of its omidirectional and wideband anti-reflection characteristics in the visible and near infrared. These can be used effectively as functional transparent electrodes in the THz frequency range as well. In this tutorial, we will present the fabrication and characterization of several TCOs, including ITO nanomaterials, graphene, and several types of bulk TCO thin films, e.g., AZO and AYZO, for THz applications.. Performance of THz phase shifters with ITO nanomaterials and graphene as transparent electrodes are presented. A graphene-based phase shifter can achieve a phase shift of π/2 at 1.0 THz with an operating voltage of ~2.2 V (rms) which is the lowest driving voltage reported for such devices, to the best of our knowledge. Article not available.
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