Structural and electrical properties of tin oxide films deposited by SILAR and spin coating techniques

Abstract

Tin oxide (SnO2) thin films are widely used in optoelectronic devices and solar cells as transparent conducting electrodes. The performance of such devices highly depends on the conductivity of tin oxide electrodes without compromising on the transmission in the desired optical region. So it is important to improve the conductivity of tin oxide thin films used as electrodes. In this work, the electrical and structural properties of SnO2 films deposited on glass substrates by Successive Ionic Layer Adsorption and Reaction (SILAR) and Spin methodology at room temperature is reported. By spin coating, the samples were deposited on glass substrates using Tin chloride in ethanol as the precursor at 1200rpm, at different concentrations. The deposited samples were annealed at 450°C for different annealing times. By the same time SnO2 films deposited on glass substrates by SILAR method using tin chloride in distilled water as the starting solution for different concentration. The samples obtained after deposition were annealed 450°C for 2 hours. Electrical conductivity measurements were done for the samples deposited by both methods and I-V characteristics for the films are plotted. For both methods, the sample prepared at 0.1M concentration and annealed for 2hrs at 450°C showed maximum conductivity retaining good transmission. And also it was found that the sample prepared by SILAR method showed least sheet resistance of the order of 141kω. The thickness of the optimised films were determined using Ellipsometry and was found to be 263nm. The structural features of the samples were analysed using X-ray diffraction and Fourier transform Infrared spectroscopy. The XRD analysis revealed that the optimised samples have peaks comparable with the standard tin oxide data and is closer for the samples deposited by spin coating method. The FTIR analysis also suggested absorption corresponding to standard absorption peaks of crystalline Tin Oxide. It is found that SILAR is a better method for film deposition as it could attain small thickness with better conductivity.