Effect of Thickness on the Optical and Electrical Properties of ITO/Au/ITO Sandwich Structures.

Tin-doped indium oxide (ITO)/Au/ITO sandwich structures with varying top and bottom ITO film thicknesses were deposited by magnetron sputtering. The effects of varying thickness of the two ITO films on the structural, electrical, and optical properties of the sandwich structures were investigated. X-ray diffraction spectra showed that by inserting an ultrathin Au film, the average grain size of the top ITO layer was significantly increased, but not for the bottom one. The optical properties of the sandwich structures were measured by transmittance measurement and spectroscopic ellipsometry. In the symmetric structure, where the top and the bottom ITO layers had the same thickness, we demonstrated that the crossover wavelength can be changed from the visible range (830 nm) to the near-infrared range (1490 nm) by increasing the top as well as bottom ITO thickness, corresponding to a plasmonic tuning ability of over 600 nm. The evaluation of this trilayer structure as a plasmonic device was asserted based on three quality factors. A comparison of the performance of this trilayer structure with conventional materials was also discussed.