Study On Preparation Of High Quality ZnO Nanofilms And Its Doping And Growth Mechanism By Ultrasonic Spray Pyrolysis

The film material of semiconductor is an indispensable for many applications,such as solar cells,gas sensing,optoelectronic devices,liquid crystal display etc.Nowadays,there are numerous technologies which have been developed to fabricate nanostructured thin films,including sputtering,sol–gel,pulsed laser deposition,chemical vapor deposition,molecular beam epitaxy,and ultrasonic spray pyrolysis(USP)method.In the above methods,USP is more nad more popular due to its low cost,non-vacuum condition,simple equipment,high rate of film formation.In this paper,the structure,property and application of ZnO were introduced,The methods of preparation and characterization are also summarized.To prepare high quality thin film,on the basis of spray pyrolysis method,the equipment of USP was designed and optimized.In the paper,ZnO thin films with good optical transmittance and electrical properties were successfully prepared by controlling the preparation process and Al doping amount.The USP of self-designed CQUTUSP-II was used in this paper.High quality ZnO and Al:ZnO AZO films were prepared on quartz substrate by USP.The micro-structure,surface morphology,optical and electrical properties were investig ated by grazing incidence X-ray diffraction(GIXRD),scanning electron microscop e(SEM),white light interferomete(WLI),ultraviolet-visible spectrophotometer(U V),fluorospectrophotometer and four point probe method,respectively.The effect of substrate temperature on the micro-structure,optical properties and the growth mechanism of ZnO films were studied.The results showed that the orientation,crystallinity,surface roughness and quality of the prepared films were poor when the substrate temperature was low.With the increase of substrate temperature,theo rientation,crystallinity,surface smoothness and quality of the prepared films were improved.Suitable substrate temperature is the key factor for the preparation of high quality films.In this article,when the substrate temperature is 550 ~oC,ZnO nanofilms prepared is uniform density,high crystallinity,obvious preferred orientation,smooth surface,in this case,the quality of the films is the best.To study the growth mechanism of ZnO thin films,ZnO thin films were prepared with different deposition time and substrate temperature.The specific growth mechanism of ZnO thin films is shown as follows:micro grains accumulation?grains'expansion?grow into certain nanostructures With the increase of substrate temperature,the nanostructure of the film will also change,as follows:irregular broken hexagonal-like structure(<450~oC)?coexisting of broken hexagonal-and sheet-like structure(450~500~oC)?regular closed packed sheets-like structure(>500 ~oC).Based on the above preparation of ZnO films by ultrasonic spray pyrolysis,the effects of mono-doped Al on the crystal structure,surface morphology,optical and electrical properties of ZnO films were investigated.It was found that when the Al/Zn atomic ratio was 4%,the prepared film had the most obvious growth along(002)crystal surface,the highest crystallinity,the smallest sheet resistance and the best quality.Finally,the experimental results are analyzed and summarized through the above experiments for further study.The paper provides a new idea for the preparation of high-quality oxide film and its doped film.At the same time,it provides the possibility of preparing high quality films for industrial production.