Research On Ultrasonic-vibration-assisted Laser Irradiation Of FTO-based Transparent Conductive Thin Films

Fluorine-doped tin oxide?FTO?transparent conductive film has a large number of virtues such as no toxicity,being easy to be laser etching,acid and alkali resistance,large area production and so on,thus it has wide application prospect in the future.With the rapid development of optoelectronic device industry,the demand for high performance and low cost of film materials is gradually increasing.Therefore many researchers have proposed to optimize the photoelectric properties of thin films using laser irradiation,so as to satisfy the needs of practical applications.However,the existing research on laser irradiation mainly focuses on the selection of laser types and the optimization of laser parameters.There are few reports on the study of ultrasonic-vibration-assisted laser processing to improve the performance of thin films.Based on this,this paper introduced ultrasonic vibration during laser irradiation process of FTO-based films.The effects of ultrasonic vibration and laser irradiation on the thin films were mainly investigated,and some meaningful results were finally obtained.1.FTO thin films were treated using ultrasonic-vibration-assisted laser annealing.The effects of laser fluence and vibration power on structure,morphology and photoelectric properties of the films were investigated.Meanwhile,the mechanism of ultrasonic-vibration-assisted laser annealing was explored.It was found that the application of ultrasonic vibration during laser annealing could cause the films to move up and down periodically together with the ultrasonic generator and thus bring about a continuous change in defocusing amount,ensuring the films to be in the optimum location to undergo laser annealing.Meanwhile,the particles in the laser-molten zone on the film surfaces could be dispersed through vibration,thus restraining agglomeration of the particles as well as realizing enhancement of the film uniformity,compactness and smoothness and reduction of the film thickness and surface roughness.The experimental results indicated that the FTO film obtained using a laser fluence of0.6 J/cm² and a vibration power of 300 W was more uniform,compact and smooth,thereby yielding the optimal photoelectric properties with an average optical transmittance?400⁸00 nm?of 84.7%,a sheet resistance of 9.0 ?/sq and a figure of meritof 2.11×10^-2?^-1,which is much higher than the untreated film(1.13×10^-2?^-1).2.Ag/FTO films with various Ag thicknesses deposited on the surface of FTO films by DC magnetron sputtering were treated using ultrasonic-vibration-assisted laser annealing.The effects of Ag thickness as well as laser spot overlap rate?SOR?and laser scan line overlap rate?LOR?on structure,morphology and photoelectric properties of the films were investigated.The results showed that when an Ag layer thickness of 5 nm,an SOR value of 90% and a LOR value of 80% were adopted,the particles on the film surface were more uniform and compact,thereby yielding the optimal photoelectric properties with an average optical transmittance?400⁸00 nm?of 81.8%,a sheet resistance of 6.3 ?/sq and a figure of merit of 2.16×10^-2 ?^-1,showing an obviously enhanced conductivity and a slightly dropped transparency as compared with the single-layer FTO films treated by ultrasonic-vibration-assisted laser annealing.3.Ag/FTO films were treated by ultrasonic-vibration-assisted laser texturing.The effect of ultrasonic vibration on the formation of grating structures was studied.It was found that the application of ultrasonic vibration could bring about periodic tiny changes of laser-excited plasma waves on the Ag particle surfaces,and thus the interference between the plasma waves and the incident laser could be more easily occurred.Meanwhile it could enable the film materials in the laser-irradiated zone to be uniformly distributed,thereby ensuring the formation of more intact,regular and uniform grating structures.The results indicated that the film obtained by using a laser fluence of 0.6 J/cm² possessed an average optical transmittance?400⁸00 nm?of 85.5%and a sheet resistance of 6.4 ?/sq,resulting in a figure of merit of 3.26×10^-2?^-1,which exhibited a remarkable improvement in overall photoelectric property as compared to that of the Ag/FTO films treated by ultrasonic-vibration-assisted laser annealing.