Effects of thermal treatment on the electrical and optical properties of silver-based indium tin oxide/metal/indium tin oxide structures

Abstract

In this article, we report the results of the study of thermal treatment effects on the electrical and optical properties of silver-based indium tin oxide/metal/indium tin oxide (IMI) multilayer films. Heat treatment conditions such as temperature and gaseous atmosphere was varied to obtain better electrical and optical properties. We obtained improved electrical properties and observed considerable shift in the transmittance curves after heat treatment. Several analytical tools such as X-ray diffraction, spectroscopic ellipsometer and spectrophotometer were used to explore the causes of the changes in electrical and optical properties. The sheet resistance of the structure was severely influenced by deposition conditions of the indium tin oxide (ITO) layer at the top. Moreover, the shift of optical transmittance could be explained on the basis of the change in refractive indices of ITO layers during heat treatment. The properties of Ag-alloy-based IMI films were compared with those of pure Ag-based ones. Some defects originating from Ag layer corrosion were observed on the surface of ITO-pure Ag–ITO structures, however, their number decreased significantly in the cases of Ag-alloys containing Pd, Au and Cu, though the resistivity values of Ag-alloys were slightly higher than those of silver. Atomic force microscopy measurement results revealed that the surface of the IMI multilayer was so smooth that it meets the required qualifications as the bottom electrode of organic light emitting diodes.