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X-ray diffraction of ZnO on ATO/ITO/glass substrate (a) after deposition and (b) before the growth. The peaks from the crystalline ITO are resolved. No peaks corresponds to ATO since it is amorphous. The inset picture shows the cathodoluminescence (CL) spectrum of ZnO on ATO with the band edge emission peak around at room temperature.
Schematic of the ZnO optical modulator device. The transparent electrodes tested were either thin semitransparent nickel or IGZO, with the IGZO providing higher transparency and lower insertion loss.
(a) Transmission spectrum for ZnO optical modulator showing effect of applied voltage. Below charge screening of the applied electric field appears to inhibit the optical modulation. (b) Percentage modulation consistent with the Dow and Redfield model, showing both the reduction of the exciton resonance at allowing more light to be transmitted, and the reduction of the transmission at due to the broadening of the excitonic band edge with electric field.
Electroabsorption spectra (triangles, circles, and squares) of a ZnO optical modulator with a nickel top electrode compared with a Dow and Redfield theoretical calculation (solid lines) for values of the unitless field parameter . The inset picture shows the electroabsorption spectra in natural units (i.e., for absorption coefficients and eV for photon energy) at (solid), (dashed), and (dotted) biases. Note that for voltages less than , the intrinsic microfields of the material had an effective which broadens the absorption edge.
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