Influence of Thermal Annealing Media on Optical and Electrical Properties of FTO, ITO and TiO₂ Films

Abstract

Metal oxides, in many cases, exhibit n-type semiconductors due to the existence of oxygen vacancies in the lattice. Therefore, the interactions of oxygen being in medium with oxygen vacancies during the annealing process can change concentrations of defects that will cause variations in optical and electric properties of such materials. However, research on such interactions for commercial FTO, ITO, and TiO₂ products has been limited. This paper summarizes the results of some experiments conducted to determine the influence of thermal annealing media on the optical, electrical properties of thin films of these products. The thermal media considered are air medium, 10⁻¹ torr low vacuum condition, and Argon gas environments, and the annealing condition is set at 450°C for 20 minutes. It is found that while FTO films change for the better after annealing, ITO films trend towards worse, and TiO₂ films have the most photoconversion efficiency (Isc = 0.27 mA, η = 0.37%) under the moderate oxygen concentration environment.