Investigation On Properties And Preparation Of Yttrium-Doped ZnO Thin Films By Sol-Gel Method

ZnO is a novelⅡ-Ⅵfamily wide bandgap compound semiconductor with outstanding electro-optical performance,higher chemical/thermal stability and be prone to dope other elements forming material with more outstanding performance. So ZnO has wide applications in many fields such as solar cells,liqiud crystal display(LCD) and shortwave luminescence parts of apparatus.A variety of thin film deposition techniques are employed to deposit zinc oxide films.Sol-gel technique offers many advantages for the fabrication of coatings, including excellent equality,strong adhesion to substrate,easy to dope at atomy level and simple technics.In this paper we study the preparation and properties of yttrium-doped ZnO thin films which have been deposited on common glass by spin coationg technique using sol-gel method.The effect of aging time,dopant concentration,pretreatment temperature,annealing temperature,layers of film plating on the crystal quality,morphology,electrical and optical properties of ZnO thin films are investigated.The relations between the structure,transmission,bandgap at the process of preparation YZO thin films by sol-gel method was researched.The results show that:(1) The forming process of thin films undoped and doped is similar from the result of TG-DTA,and don't exist changes with yttrium element related.So the majority of doped yttrium enters the crystal lattice.(2) The results of XRD shows that the YZO thin films assume hexagonal wurtzite structure.The crystal equality and preferential c-axis oriented are the best, the(002) peak is strongest,the FWHM is least when the optimized growing parameters are:72h(aging time),300℃(pretreatment temperature),500℃(annealing temperature) and 5 layers.The crystal quality and the grain size of YZO thin films decrease and the FWHM increases with the increase of dopant concentration.(3) The analysis of AFM indicates that the YZO thin films are even and compact. The extended aging time is propitious to the preferential c-axis oriented growth and increase the coarseness of thin films. (4) The transmission spectrum of all thin films suggests that the average transmittance in the visible range(380nm-760nm) is beyond 85%.The transmittance can reach 90%when best condition.This result is coincident with the result of XRD.(5) Each parameter influences the bandgap of thin films from the(ahv) ~2～hv curve.The primary factor is dopant concentration,the secondary factors are annealing temperature and layers of film plating.(6) The resistivity of thin films decreases first then increases with the increase of dopant concentration.The minimum resistivity is 3.37×10~2Ω.cm with dopant concentration 1at%.