The Preparation Of The Middle Infrared Transparent Conductive CuAlO₂Film And The Research Of Doping CuAlO₂Film On Properties Improvement

As the first discovered P-type semiconductor, the delafossite CuAlO₂thin filmmaterials have been a good development at home and abroad. Since the majority oftransparent conductive oxide thin films are transparent in the visible optical range ofthe solar spectrum, but strong reflective in the infrared range. And CuAlO₂film hashigh transmittance in the middle infrared range because the wide bandwidth, whichmakes the study of p-type CuAlO₂thin film more significance. Compared with then-type semiconductor film, the conductivity of p-type semiconductor film is very low.It’s not conductive to the application, so it is important to improve the conductivity ofCuAlO₂thin film. This paper studied the differences of CuAlO₂thin film whichprepared by the use of different methods on crystal structure and optical、electricalproperties. And it focuses on the properties improvement of Ca²⁺、Fe³⁺、Ti⁴⁺dopedCuAlO₂thin film.The experimental results show that RF magnetron sputtering and sol-gel methodby comparison, the crystal orientation of magnetron sputtering performance bettersingle crystalline. The transmittance of CuAlO₂thin film in the middle infrared rangeis about75%⁹0%by both preparation methods. But on the whole, the transmittanceof CuAlO₂thin film which prepared by sol-gel method is lower. That’s because thefilm evenness which prepared by sole-gel method is lower than RF magnetronsputtering, leading to larger surface scattering. The minimum square resistance of themagnetron sputtering film is5.4K/□, and the sol-gel method is10.1K/□. As thesingle orientation and lower grain boundary scattering of the magnetron sputteringfilms, films show higher conductivity.Due to the sol-gel films have the advantages of low cost, simple to make, easy tocontrol the doping ratio. So we doped foreign ion by the sol-gel method in this paper,this paper chose three kinds of ion valence state. The research of doping CuAlO₂filmmainly about improving the conductivity and transmittance in the middle infraredregion. The doping experiments annealing at950℃based on the last experimentalconclusion. Delafossite structure of CuAlO₂thin film was not destroyed by doping. With the increasing of doping concentration, the peaks left shift. This is becauseCa²⁺、Fe³⁺、Ti⁴⁺ions substitute Al. With the increasing amount of impurity doping, theaverage transmittance decreased in the infrared region. But the transmittance ofFe³⁺-doped CuAlO₂thin film decreased obviously, and the average transmittance ofCa²⁺-doped film is much lower than the Ti⁴⁺-doped film in the middle infrared region.The square resistance of undoped film is10.1K/□. With the increasing of dopingcontent, the square resistance of film first decreased and then increased. Especiallywhen Fe³⁺-doped content is5%, the square resistance is decreased to3.5K/□.While the transmittance of film did not reduce largely in the middle infrared region.This shows that Fe³⁺-doped film have good conductivity and transmittancerelatively.