Ultrasonic-vibration-assisted laser annealing of fluorine-doped tin oxide thin films for improving optical and electrical properties: Overlapping rate optimization

Abstract

An ultrasonic-vibration-assisted laser annealing method was developed to enhance the performance of fluorine-doped tin oxide (FTO) thin films. The influences of ultrasonic vibration, laser scan line overlapping rate (LOR) and laser spot overlapping rate (SOR) on surface morphology, FTO layer thickness, RMS roughness, crystal structure and photoelectric properties of the FTO films were investigated. The results indicated that the presence of ultrasonic vibration during laser annealing could significantly enhance the film compactness, and using moderate LOR and SOR values resulted in significantly decreased FTO layer thicknesses and RMS roughnesses as well as slightly increased crystallite sizes, thus yielding significantly improved optical transmittance values and slightly enhanced electrical conductivity values. It was found that the optimal LOR and SOR values for ultrasonic-vibration-assisted laser annealing of the FTO films were 80% and 90%, respectively. The as-obtained film possessed the best overall photoelectric property with an average transmittance (400–800 nm) of 85.9%, a sheet resistance of 8.7 Ω/sq and a figure of merit of 2.51 × 10–2 Ω–1. This work may be of great significance in terms of performance optimization of transparent conducting oxide (TCO) thin films.