| Transparent conductive oxide film?TCOs?,as a transparent thin film transistor,has been widely used in smart phones,liquid crystal displays and transparent electronic products,because of its low resistance,high optical transparency,good wear resistance,relatively stable physical and chemical properties and good adhesion.Among the present three systems of TCO films?Sn O2-based,In2O3 based and Zn O based?,In2O3 based films is the most mature one in industrial production.However,the In2O3-based thin films has been limited to use due to unstable chemical properties,expensive and toxic elements.The Sn O2transparent conductive films is considered to be the best substitute for In2O3based film because of its excellent chemical stability,low cost,easy preparation and its poor conductivity can be improved by doping.Therefore,it is of great significance to systematically study the influence of different dopants on the properties of Sn O2 transparent conductive films.In this paper,Sn O2-based transparent conductive thin films is prepared by combining the sol-gel method and the vapor deposition method organically,and take the float glass as the substrate.This technology combines the advantages of traditional sol-gel method and vapor deposition method,and has the advantages of simple preparation method,low production cost,stable chemical properties and strong adhesion.The electrical properties of Sn O2-based thin films were characterized by their resistivity,which was measured by FT-330 four probe resistivity/square resistance tester in this study;The optical properties of the films were characterized by its transmittance in the visible region,measured by TU-1901double beam UV-Vis spectrophotometer;The morphology and structure of the film surface were observed by Apreo scanning electron microscope?SEM?;The phase and crystallinity of the films were measured by D8 The chemical properties?element composition and chemical state?of the film surface were analyzed by ESCALEB 250 X-ray photoelectron spectroscopy?XPS?.The emphasis of this study is to dope some dopants into Sn O2 thin films in order to improve the photoelectric properties of Sn O2 thin films.Two main types of dopants are investigated in this study,including metallic elements and non-metallic elements.Among them,metallic elements are mainly represented by Sb which is close to Sn in the periodic table of elements,La which has good stability in the transition metal elements and W which has high valence difference in doping.Non-metallic elements are represented by F,N,S which are close to O in the periodic table of elements.The effect of different doping content of different elements on the photoelectric properties,surface morphology and microstructure of Sn O2-based films are studied,and the doping mechanisms are systematically discussed.Details are as follows:1. Sb,W,La doped Sn O2-based transparent conductive thin films were prepared by sol-gel- evaporation method.When Sb Cl3 was used as the dopant,the comprehensive photoelectric performance index of Sn O2:Sb films increased first and then decreased with the increase of dopant content,reaching the maximum of 6.187×10-3?-1 when the dopant content was 12mol%;The comprehensive photoelectric performance index was 3.312×10-3?-1 with 4 mol%WCl6 as dopant.With 4 mol%La?NO3?3·6H2O as dopant,the comprehensive photoelectric performance index was 1.96×10-3?-1.Obviously,Sn O2-based films with Sb Cl3 as dopant had better comprehensive photoelectric properties.2. Sn O2-based transparent conductive films doped with F,N and S were prepared by sol-gel-evaporation method.When 14 mol%Sn2F was used as the dopant,the comprehensive photoelectric performance index of Sn O2:F films was the maximum value of 4.944×10-3?-1;While when urea or thiourea were used as the dopant,the electrical performance of Sn O2:N and Sn O2:S films could be improved,but the optical transmittance of Sn O2:N and Sn O2:S films were damaged severely,and the maximum comprehensive photoelectric performance indexes were 2.31×10-4?-1and 4.37×10-4?-1,respectively.Sn O2-based films with excellent electrical and optical properties cannot be obtained by doping urea or thiourea.3. The Sn O2 films doped with metal or non-metal elements were all tetragonal rutile phase structure,and no new phase formed in doping process.When Sb Cl3,WCl6 and La?NO3?3·6H2O were used as dopants,the surface morphology of Sn O2 films were shell,pebble and irregular polyhedron,respectively.While Sn2F,urea and thiourea were used as dopants,the surface morphology of Sn O2 films were pyramidal,irregular quadrangular/tetragonal biconical and irregular quadrangular/triangular/tetragonal biconical,respectively.Among them,the particles in Sn O2:F and Sn O2:Sb films had clear edges and corners,high photon utilization and good comprehensive photoelectric performance.4. Doping improved the electrical properties of Sn O2 thin films greatly.The main mechanism of doping was that doping introduced donor level or acceptor level into the band gap and effectively changed the band gap width of Sn O2.Consequently,the electrical properties of Sn O2 thin films were improved,and at the same time caused photoelectric effect,so that its transmissivity in the visible light area was reduced.Some dopants,such as urea and thiourea,had great influence on the optical properties of Sn O2.Different dopants had different effects on the energy level structure,and further affected the cell structure,surface morphology and comprehensive photoelectric properties.In addition,due to the different doping positions,there was a certain gap between the radius of substituting ions and the radius of substituted ions in different dopants,which resulted in different degrees of lattice distortion,and also had a certain impact on the microstructure,surface morphology and photoelectric properties of Sn O2 films. |
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