| Since photoelectric devices such as Flat-panel displays,solar cells,light emitting diodes(LEDs),gas sensor,energy saving glass are widely used,the market demand of transparent conductive films is further expanded.The indium tin oxide film(ITO)film is most widely applied at present,but it is restricted the practical application of ITO thin films because main component of the ITO thin film is a rare expensive and toxic element Indium.ZnO is a II-VI semiconductor material with wide band-gap,which has hexagonal wurtzite structure.Transparent conductive oxide thin film based on ZnO has become a hot issue of transparent conductive thin films field and preferred materials instead of ITO films not only because of their comparable optical and electrical properties(high optical transparency in the visible range,low electrical resistivity)to ITO films,but also because of their lower price and higher thermal and chemical stability under the exposure to hydrogen plasma than ITO.In this paper,doped and High quality of the transparent conductive oxide thin films based on ZnO were prepared by radio frequency(RF)magnetron sputtering with zinc oxide ceramics target on glass substrate.The films obtained were characterized and analyzed by X-Ray Diffraction(XRD),Scanning Electron Microscope(SEM),X-ray photoelectron spectroscopy(XPS)and UV-visible infrared spectrophotometer.The conduction mechanism has been analyzed and the electrical properties had been investigated by Van der Pauw method.It was changed such as substrate temperature,oxygen argon ratio and process conditions,power,air pressure in the process of preparation.We studied the influence of various parameters for the thin film photovoltaic performance and it is concluded that the best process parameters through orthogonal experiments.The experimental results showed that the transparent conductive oxide thin films based on ZnO had better structural,optical and electrical properties.XRD showed that the obtained films were poly-crystalline and highly orientation growth with the C-axis perpendicular to the substrate surface.The spectral analysis results of the transparent conductive oxide thin films based on ZnO show that the average transmittance are above 80%in the visible region of the thin film samples.The electrical performance results of the films show that the resistivity of AZO thin films are greatly influenced by the power and argon oxygen ratio.The resistivity of the transparent conductive oxide thin films based on ZnO is reduced,for the increased mobility with the increment of power.The resistivity of the films increased with the increasing rate of the oxygen argon and mobility decreased.It was studied that the annealing temperature and annealing atmosphere such as vacuum,air atmosphere influence on photoelectric properties of the transparent conductive oxide thin films based on ZnO in this paper.Results show that,the resistivity of the films decreased,and the carrier concentration and mobility increases with the increase of annealing time and temperature under 400?.Compareing the samples annealing in different atmosphere we can found that the oxygen vacancy defects is an important source of film carrier,which will improve electrical conductivity of the AZO films.This paper explored the conductive mechanism and main factors which will definitely influence the properties of the films by changing the doping concentration and doping type.Theory and experiment has proved that the conductivity of ZnO first increase then decreases with the increase of A1 doping concentration.When A1 doping concentration was 2%,the conductivity of thin films of ZnO will be best.It can be explained that when doping concentration is low,the increase of doping concentration will increase the concentration of carrier and make the resistivity decreases and when the doping concentration too high,free carrier concentration increased a little,the impurity in the film increase a lot,this enhanced free carrier scattering and the free carrier mobility decreases,eventually lead to higher resistivity.Al,H codopping results show that H will not only affect the structure of AZO thin films,but also play the role of donor to improve the conductivity of AZO thin films.the H doping is helpful to obtain high performance AZO transparent conductive films.Finally,the paper design aging test to study the transparent conductive oxide thin films'aging characteristics and physical mechanism based on ZnO.The transparent conductive oxide thin films based on ZnO were placed under the condition of temperature at 80 ? and humidity at 80%for 24 days.Regularly they were measured the sheet resistance every three days comparing with the one placed indoor environment and the others with other organic material layer coated on the surface to study the performance of the thin films' electrical aging process.The results shown that under high temperature and high humidity environment,film aging is accelerated and it also would exacerbate the aging process when organic matter covered.Annealing the sample after the aging experiment again in hydrogen found that electrical performance of thin film has recovered,some sample will even better than the initial electrical conductivity.This shows that film performance deterioration aging is mainly caused by adsorption of water and oxygen in the air,and the process is reversible.But this process can only be partially reversible and the film has a permanent degradation in performance in the film with organic matter covered the surface.Above all for the study of the organizational structure and photoelectric properties of the transparent conductive oxide thin films based on ZnO,we got the AZO thin films prepared by RF magnetron sputtering method of optimum technological conditions for:doping concentration was 2%,the argon oxygen rate 0:30,substrate temperature 300?,3 pa work pressure,the distance of target and substrate 6 cm,power 120 w,the annealing temperature 400 ?.The transmittance of AZO thin films which is prepared under the optimum technological condition is as high as 80%,the resistivity can be reduced to about 10-4?·cm.Therefore AZO thin film has the characteristics of low resistivity,high transmittance,it can be used as a transparent electrode in optoelectronic devices. |
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