The Preparation And Investigation Of ZnO Transparent Films

In recent years,semiconductor materials zinc oxide(ZnO) attracts more and more attentions than ever before.ZnO has large direct band gap(3.37 eV in room temperature). Due to their excellent physical and chemical properties,ZnO films have many realized and potential applications such as surface acoustic wave devices,ultraviolet photo-detectors, planar optical waveguides,transparent electrodes,piezoelectric devices,gas sensors,etc. Moreover,another important application of ZnO materials is preparation for the transparent and conductive thin films.There are so many technique methods to be used to deposit ZnO films,such as magnetron sputtering,metal organic chemical vapor deposition,and the research progress has been made.But the magnetron sputtering,metal organic chemical vapor deposition systems are complicated and the cost of the systems is high.A new method must be considered,if we want to industrially produce ZnO transparent and conductive thin films.Thermal evaporation is cheaper to prepare,easy to operate,compared to magnetron sputtering,metal organic chemical vapor deposition methods,so it's the technique applicable to industrial production.Thin films whether small or large-area can be obtained by this method.But the thermal evaporation method is not applicable to directly evaporate ZnO,so thermal oxidation also has been used.In this research,in the first step,Zn films were deposited by thermal evaporation technique and then ZnO transparent and conductive films with highly preferred c-axis orientation were prepared through thermal oxidation operation. The process,characteristic and influence elements for the growth of the films with preferred growth orientation were discussed.Most importantly,a new method has been creatively discovered in oxidizing Zn thin films,that is step-by-step-oxidation method.And the influence of different oxidation methods making ZnO transparent and conductive thin films has been investigated.And the structure and optical property has been tested by X-ray diffraction and transmitted spectrum.The results show the quality of ZnO transparent and conductive thin films made by step-by-step-oxidation method is much better than direct-oxidation method,and the highest light transmittance of thin films is over 90%.