Flash lamp annealing of indium tin oxide thin-films deposited on polyimide backplanes

Abstract

Xe-arc flashings of 0.4–1.0ms in pulse duration annealed indium tin oxide (ITO) thin-films deposited on flexible polymeric substrates at room temperature. As flexible substrates, highly transparent polyimide (PI) thin-films of 16μm in thickness were prepared on a carrier glass. Measuring optical characteristics of the ITO and the PI thin-films and using the Maxwell equations, we estimated complex refractive indices of ITO and PI materials. With the use of these optical properties, one-dimensional conduction/radiation heat transfer simulation was carried out to predict the temperature variations in the specimens, assuring that the temperature in the ITO thin-film during the flash lamp annealing (FLA) process exceeded its crystallization point. Experimental FLA process resulted in a significant enhancement of the electrical conductivities as well as in a slight increase of optical transmittances of the specimen and was compared with the conventional furnace annealing (CFA) process of 1h. Microscopic changes in the specimen during the annealing processes were compared using the X-ray diffraction pattern, atomic force microscope, and scanning electron microscope (SEM) measurements. Especially SEM images confirmed that sudden degradations in the electrical conductivities of ITO thin-films observed under higher power FLA or higher temperature CFA conditions were strongly related to the physical damages in the thin-films, which were incurred due to the thermal expansion mismatch between the ITO thin-film and the PI substrate at high temperatures.