Preparation And Transparent Conductive Properties Of Ultra-thin Silver Films

In recent years,with the rapid development and application of flexible optoelectronic devices,thin film materials with high transparency and good electrical conductivity,which can be bent and folded to a certain extent,have been widely concerned.Indium tin oxide film(ITO),as a typical representative of transparent conductive film,has the characteristics of high transparency and very low resistivity,but an important condition that cannot meet the needs and development of flexible electronic products and related industries is its high price and poor mechanical flexibility.Metals can exhibit high electrical conductivity and excellent mechanical properties,so transparent and extremely thin metal films with high electrical conductivity and good mechanical flexibility are considered as potential substitutes for indium tin oxide(ITO)films.Silver is a soft glossy transition metal element with high electrical and thermal conductivity,and silver films are cost-effective compared to gold films and exhibit higher ductility compared to copper films.However,due to the poor adhesion between the metal atoms and the substrate,the silver film on the substrate usually presents a three-dimensional island growth pattern,so the thickness has a great influence on the performance of the metal film,and the metal film generally has a threshold thickness.When the thickness of the film is smaller than the threshold thickness,the growth surface of the film will show a discontinuous island structure,and the electrical properties of the film grown with this structure are relatively poor.However,with the gradual increase of film thickness,the island structure will gradually change to the layered growth mode,and then form a more continuous film.Therefore,reducing the threshold thickness of silver film and ensuring good conductivity is the key to obtain an ideal metal transparent conductive film.This paper focuses on the preparation and properties of extremely thin silver transparent conductive films.In this paper,systematic theoretical and experimental research has been carried out on the acquisition of optical constants of extremely thin silver films,the selection and thickness optimization of infiltration layer,the preparation and thickness optimization of extremely thin silver films,and the exploration of silver and graphene composite films,and thermal stability research of extremely thin silver transparent conductive films..The main work and achievements are as follows:(1)Extremely thin silver films of different thickness are prepared by means of resistance thermal evaporation technology.The optical constants of extremely thin silver films are studied by ellipsis method,and the specific optical constants of extremely thin silver films are given.The changes of optical constants of extremely thin silver films are analyzed,and the obtained optical constants provide basic conditions for subsequent theoretical simulation.The surface morphology of silver thin films was obtained by field emission scanning electron microscopy,and the variation of surface morphology with thickness was analyzed.(2)The threshold thickness of silver film was reduced by the introduction of the infiltrating layer.Firstly,appropriate infiltrating layer was selected through experiment and theoretical analysis to optimize the thickness of the infiltrating layer,and then silver films of different thickness were deposited on the infiltrating layer.After analyzing the transmittance,square resistance and surface morphology of silver films,transparent conductive silver films with good comprehensive performance were obtained.Subsequently,an innovative method of approximate mixing was proposed for the aluminum infiltrating layer.The infiltrating layer and silver film were deposited in layers to maximize the infiltrating effect of the infiltrating layer,and then a transparent conductive silver film with better comprehensive performance was obtained.(3)The preparation of graphene and silver composite film is carried out by using a suspended self-service single graphene and silver film composite.Through different composite structures,explore the optical and electrical properties of composite films,and analyze whether the introduction of graphene films can replace the infiltration effect of infiltrating layer on silver films,or have better infiltration effect.Finally,the thermal stability of the very thin silver transparent conductive film with good performance was studied,that is,the transparent conductive film was annealed in vacuum.The thermal stability of the very thin silver transparent conductive film was further analyzed by annealing the silver film at different temperatures.