Effect of Nitrogen Flow Rate During Annealing on Structural and Electro-optical Properties of ITO Thin Films Deposited by Ultrasonic Spray Pyrolysis

In this study, we first fabricated ITO thin film samples on glass substrates at 300 degrees C temperature by ultrasonic spray pyrolysis technique. Then three different groups of samples were prepared under three different medium conditions. Some of these samples were annealed at 475 degrees C in an atmospheric medium and the other two group of samples were annealed at the same temperature, but in different media in which flowing N-2 with 150 and 250 L/h. Structural, morphological, electric and electronic, and optical properties of these samples were determined by X-ray diffraction, scanning electronmicroscope, atomic force microscope, ultraviolet-visible spectrometer, and cryostat measurements. These measurements showed that increasing nitrogen (N-2) flowrate in annealing improved the structural properties of the films by almost doubling crystallinity, but bandgap energy of the samples decreased. It was seen that with this increasing the N-2 flow rate slightly reduced the transmittance of the films. In addition, Hall measurements have shown that the resistivity of the films decreased from 1.65 x 10(-2) to 1.19 x 10(-2) Omega cm by introducing the N-2 gas. It has also been shown that annealing under N-2 gas flow is a method that can be used efficiently to reduce the Oxygen (O-2) ratio in the ITO thin films.