Preparation And Photoelectric Properties Of Transparent Conductive Films Of Tin-Doped Zinc Oxide

Zinc oxide: a kind of direct band gap wide band gap semiconductor material.The crystal is mainly composed of ion bond.Due to the low symmetry of ZnO crystal structure,the band structure is relatively complex.At room temperature,the band gap is about 3.37 ev,which determines the high transmittance of visible light and near-infrared light.Due to the defects of zinc and oxygen vacancy in the internal gap,intrinsic ZnO has certain conductivity,which can be greatly improved after doping,especially the transparent conductivity of n-ZnO,which is very likely to replace indium tin oxide ITO and fluorotin oxide FTO in solar cells as transparent electrodes.The doping of n-ZnO mainly includes B,Al,In,Ga of group III and Si,Sn of group IV.Aluminum doped zinc oxide ZAO is environmentally friendly and low-cost.It is most likely to be used as transparent electrode instead of ITO and FTO in solar cells.There is a characteristic of ZAO that is not acid and alkaline resistant,so it is limited in many applications.Tin doped zinc oxide TZO is rarely reported.Compared with Al,Sn is more nonmetallic,and TZO is likely to improve its stability in acid-base environment.Compared with group III elements with the same doping concentration,Sn⁴⁺ can replace Zn²⁺ to produce two free electrons,which can obtain higher carrier concentration,and the difference between Zn²⁺ and Sn⁴⁺ ion radius is not significant?Rzn2 + = 0.074 nm,Rsn4 + = 0.069nm?,Sn can replace the position of Zn,so that there will be no large lattice distortion.Theoretically,the resistivity should be lower than ITO,GZO and ZAO,But in fact,the current conductivity of TZO can not meet the practical application of solar cells,and its influence mechanism needs further study.In this paper,Tin doped ZnO transparent conductive films were prepared by RF magnetron sputtering,and the deposition parameters were studied and analyzed.In the experiment,Tin doped ZnO ceramic target was used as sputtering target,and RF magnetron sputtering system was used to adjust the depositionparameters?working pressure,sputtering power,substrate temperature,oxyhydrogen concentration in working gas?.XRD,SEM,TEM,UV-Vis spectrophotometer,Raman spectrum,fluorescence photoluminescence spectrum and four probes were used to study the structure,morphology,composition and electricity of the film and optical properties.The main results are as follows:1.The results of sputtering pressure change: adjusting the sputtering pressure 0.1-14 Pa to prepare tzo thin films,the grain size and peak intensity near640 nm of PL spectrum increase first and then decrease with the pressure,At 0.7Pa,the maximum grain size is 25.66 nm,and the peak relative strength of PL spectrum at 640 nm is the largest.With the increase of sputtering pressure from0.1 to 14 Pa,the film resistivity also increases first and then decreases.At 0.5 Pa,the grain size is the largest,but the maximum resistivity is 18.1 × 10-4 ?· cm At Pa,the grain size of the film is the smallest,but the film is denser,and its resistivity is 2.7×10-4?· cm.2.Results of power change: the single peak of XRD and the lattice diffraction patterns of TEM show that the films are prepared by magnetron sputtering ZnO:Sn The film has good single crystal properties.The transmittance of all samples is over 89% in the wavelength range of 400-900 nm.The transmittance decreases with the increase of the roughness Rq.In the fluorescence photoluminescence spectrum,308 nm peaks near 320 nm,430 nm and 640 nm excited the Raman shift,gap zinc and zinc tin defects,respectively.The peak position changes are related to the crystal stress and strain.The Raman peak near 568 cm-1 corresponds to the A1?LO?first-order phonon scattering vibration mode,which is related to the electric dipole pair formed by zinc and oxygen vacancy in the crystal gap deflecting in the electric field.The 1098 cm-1Raman peak is the second-order phonon vibration mode.3.Results of temperature change: at 50-250 ?,there are?002?diffraction peaks and?004?diffraction peaks near 74 ° in the temperature range of50-250 ?.This shows that the incorporation of SnO₂ does not change either the phase of SnO₂ or the crystal structure of ZnO,that is,the c-axis preferred growthperformance perpendicular to the substrate direction.With the increase of temperature,the change trend of surface roughness Rq decreases first,then increases and then decreases.With the increase of temperature,the change trend of surface roughness Rq decreases first,then increases and then decreases.There are three characteristic peaks near 315 nm,420 nm and 620 nm,the corresponding energies are about 3.82 e V,2.86 e V and 1.94 e V,respectively.The minimum resistivity of the sample film is 0.64×10-2 ?·cm at 50 ?.It can be seen that with the increase of temperature,the resistivity will gradually increase and then decrease.