Study On The Preparation And Optical Properties Of Preferred Orientation ZnO Thin Films By EFMS Technique

ZnO is a II-VI wide bandgap semiconductor material.The natural doping of semiconductors due to oxygen vacancies and zinc gaps is n-type,which makes that the semiconductors have good transparency,high electron mobility,broadband system and strong room temperature luminescence.Its good transparency can be used as a transparent electrode in the display screens of various electrical appliances,and can also be used as a thermal protection window and an electronic device such as a thin film transistor and a light emitting diode,etc.So it has a very good practical value.Nowadays,there are many kinds of preparation techniques for ZnO film.Magnetron sputtering technology has been widely applied because of its high deposition rate,low cost and good optical properties of ZnO thin films.However,the films prepared by magnetron sputtering technology need to be improved in grain orientation,grain size and surface roughness.This paper used an improved magnetron sputtering instrument for the preparation of ZnO film.The improved method is to add a stainless steel metal filter electrode in front of the substrate,and the improved technology is called EFMS technology.The film prepared by this technique has good surface uniformity,obvious crystal orientation,narrower half width and high crystallinity,thereby improving its optical properties.In this paper,the effects of different deposition conditions on the structure,preferred growth and optical properties of ZnO thin films grown on r,a,c and m sapphire substrates were investigated by EFMS.The content of this paper is as follows:(?)Firstly,three groups of Zn O thin films were prepared by changing the deposition temperature,deposition pressure and oxygen-argon flow ratio on r-plane(11-20)sapphire substrate by EFMS technology.X-ray diffraction and field emission scanning electron microscopy(SEM)were used to study the structure and surface morphology of ZnO films;Optical properties such as transmittance,refractive index,and extinction coefficient were characterized using an UV/VIS/NIR spectrophotometer and ellipsometry.The results show that:(1)The ZnO prepared on the r-plane substrate has only(1-102)diffraction peaks,indicating that the prepared ZnO grows along(1-102)orientation.the ZnO film with the a-plane is grown on the R-plane sapphire.(2)When the temperature is 411 ?in the temperature range,the particles on the film surface is very small,and the crystal quality is the best.With the increase of temperature,(1-102)the half width of the peak begins to widen,and the crystalline quality becomes worse with the increase of temperature,and the surface grain grows and the roughness increases.(3)When the pressure is 0.75 Pa,the particles on the film surface are uniform and no agglomeration.When the pressure is up to 1.2Pa,the crystalline quality is poor,and the surface particles are agglomerated,and the corresponding wavelength of refractive index and extinction coefficient is red shifted.(4)When the ratio of oxygen to argon is 5:5,the crystallization of thin films is best,and the surface particles are smaller.The refractive index changes slowly in the visible range.(?)Next,a-plane(11-20),c-plane(0001),and m-plane(10-10)sapphire were selected as substrates for the preparation of ZnO thin films.Then the ZnO film was prepared on the a-plane and c-plane sapphire substrate by changing the deposition temperature under the condition that the other substrate conditions were not changed.Finally,the oxygen-to-argon ratio parameters were changed on the m-plane to study the growth ratio and optical properties of the zinc oxide on the m-plane.The results showed that the ZnO films on the a-plane and c-plane sapphire substrate were only(0002)and(0004)diffraction peaks,which indicated that the c-plane ZnO film was grown on the a-plane and c-plane sapphire.The preferential growth of ZnO thin films grown on m-plane substrate changes significantly with the oxygen-argon ratio,and more or less argon gas is not conducive to the preferred growth of ZnO thin films.When the oxygen-argon ratio is 5:15,only the(10-10)and(20-20)diffraction peaks of the ZnO thin film indicate that the m-plane ZnO thin film is grown on the m-plane sapphire.