Highly Transparent Conducting Indium Tin Oxide Thin Films Prepared by Radio Frequency Magnetron Sputtering and Thermal Annealing

High-quality ITO (indium tin oxide) films were grown by radio frequency (RF) magnetron sputtering and post thermal annealing. Both the thermal annealing temperature and the atmosphere significantly influenced the optical and electrical properties of ITO films. The as-grown 110-nm-thick ITO film showed an optical transmittance of 34.2% at a wavelength of 550 nm and electrical resistivity of 9.2x10(-4) Omega cm. Notably, the ITO films annealed at 850 degrees C for 1 min in nitrogen ambient led to a significantly improved optical transmittance (97.3%) and the low electrical resistivity of 1.3x10(-4) Omega cm, while those annealed in air or oxygen ambient produced poorer electrical properties despite their good optical transmittance owing to the presence of oxygen. The high quality of the ITO film annealed in nitrogen could be attributed to the combined effects of effective suppression of oxygen incorporation into films (thus maintaining oxygen vacancies in the ITO film), enhanced Sn doping, and improved the crystallinity with larger grain size.