Frequency-dependent complex conductivities and dielectric responses of indium tin oxide thin films from the visible to the far-infrared

Abstract

Transparent and conducting indium tin oxide (ITO) thin films form an integral part for various optoelectronic devices. In this paper, we report the frequency-dependent complex conductivities and dielectric responses of several sputtered ITO thin films with thicknesses in the range of 189962 nm by using terahertz time domain spectroscopy (THz-TDS), optical reflectance spectroscopy, and electrical measurements. The plasma frequencies are verified to be from 1590 to 1930 rad. THz, while the scattering times are in the range 67 fs based on the Drude free-electron model. The mobilities of the above ITO thin films are calculated to be 32.7-34.2 cm2 V-1 s-1, whereas the carrier concentrations lie in the range 2.79-4.10 x 1020 cm -3. The electrical properties derived from the THz-TDS technique agree well with those determined by Hall measurement. Parameters for the complex dielectric function suitable for ITO in the range 0.22 and 4450 THz are also determined. © 2010 IEEE.