Microstructure-Property relationships in thin film ITO

Polycrystalline tin-doped indium oxide (ITO) thin films were prepared by pulsed laser deposition (PLD) with an ITO (In2O3-10 wt.% SnO2) target and deposited on borosilicate glass substrates. By changing independently the deposition temperature and the oxygen pressure, a variety of microstructures were deposited. These different microstructures were mainly investigated not only by transmission electron microscopy (TEM) with cross-section and plan-view electron micrographs, but also by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction. Composition changes in ITO thin films grown under different deposition conditions were characterized by energy dispersive X-ray spectroscopy (EDX). The optical and electrical properties were studied respectively by UV-visible spectrophotometry and a four-point probe. The best compromise in terms of high transmittance (T) in the visible range and low resistivity (ρ) was obtained for films deposited between 0.66 and 2 Pa oxygen pressure (PO2) at 200 oC substrate temperature (Ts). The influence of PO2 and Ts on the microstructure and ITO film properties is discussed.