Research On Preparation And Photoelectric Properties Of Delafossite-type Infrared Transparent Conductive Films

Transparent conductive oxide thin films have been studied for a long time, the most widely used materials are n type structures, the related research of the p-type material is less. Since we found the delafossite structure of ternary oxide materials（such as CuAlO₂）,it gets a high attention, this kind of material is a p-type semiconductor, it has a certain transmittance and conductivity. But at present most studies of the transmittance are confined in the visible band, and the conductivity is not ideal.If we do more research by doping and so on,improving the material properties,it can be widely applied in military, industry and daily life with broad prospects,which will greatly promote the development of transparent oxide semiconductor,and has a very important significance.The research topic of this paper comes from the National Natural Science Foundation of China, the project name is: The Research of Photoelectric Properties and Preferred Orientation Preparation of the Delafossite Structure CuXO₂ Infrared Transparent Conductive Films, the project number is: NO. 11404129. The performance index of this project: the transmittance rate>80%, the conductivity>2S/cm.In this paper, we do the following research about this delafossite transparent conductive oxide films:1. we prepared Ca²⁺、Zn²⁺、Fe³⁺ doped CuAlO₂ and CuCrO₂ films on quartz substrates by sol-gel method and changed element doping concentration in the process of preparation. From the crystal structure, the elemental valence state, micro-structure,transmittance, conductivity these aspects to research the performance of film sample groups. The results show that CuAlO₂ and CuCrO₂ thin films were successfully prepared by this method, after doping the films have different degrees of improvement in the transmittance and conductivity.7 percent Fe³⁺ doped CuAlO₂ thin films has the best transmittance of 87% in the near infrared band;5 percent Zn²⁺ doped CuCrO₂ thinfilms has the best conductivity reaches 3.88S/cm.2. we use Cu target and Al target as sputtering source and deposit thin films on sapphire substrate by DC-RF Co-sputtering. We change sputtering power, sputtering time and sputtering atmosphere in the process of preparation. Through the contrast experiment, the optimum sputtering conditions were obtained:Cu:40w,Al:160w,sputtering time 20 min, pure argon atmosphere.Under this condition we obtain pure CuAlO₂ film, the film’s thickness is 116 nm,surface roughness RMS is 11.7nm.Compared with the sol-gel method, this experiment improves the film’s surface morphology,the transmittance reaches 83% in the infrared band3. We change the placed time, temperature and humidity of the environment and observe of CuAlO₂ thin films’ morphology stability.The results show that the length of placed time hardly change the morphology of the films, the films’ morphology defects generate with the change of temperature and humidity, and the higher humidity or temperature make more morphology defects.