The effects of thermal annealing on the structural and electrical properties of zinc tin oxide thin films for transparent conducting electrode applications

The as-deposited and annealed Zinc tin oxide (Zn2SnO4) thin films, deposited by electron beam evaporation technique, were characterized for the structural, optical and electrical properties. The x-ray diffraction technique revealed the amorphous nature of as-deposited thin film while the films annealed at 400, 500 and 600 degrees C in air were found to be polycrystalline in nature. The phase change from amorphous to crystalline Zn2SnO4 resulted in the higher resistance as revealed by resistance versus temperature measurements. From the Hall effect measurements, the as-deposited film shows the electron mobility and carrier concentrations (electron) equal to 33 cm(2)/V.s and 8.361 x 10(17)cm(-3) respectively. The agglomeration of grains in annealed thin films are observed by Atomic Force Microscopy (AFM) technique. The peaks in Optical transmission spectra, observed by using the UV-Vis spectroscopy confirm the creation of sub levels between conduction band minimum and valence band maximum after annealing. The band gaps calculated by Tauc plot explore the possibility of shifting the Fermi level towards valence band maximum after thermal annealing.