The Study Of The TiO₂-based Sandwiched Multilayer Transparent Conductive Films

TiO₂/Ag/TiO₂（TAT） multilayer transparent film was deposited by radio frequency（RF） and direct current（DC） magnetron sputtering. We explored its applications to TAT based photodetectors as transparent electrodes. The main study work includes the following several aspects:1. TiO₂ and Ag films were grown respectively by RF and DC magnetron sputtering. The effects of sputtering power and pressure on deposition rate of TiO₂ and Ag were studied. When the argon （Ar） pressure exceeds 0.4Pa, the deposition rate will increase as the pressure decrease. Due to the settings of the sputtering apparatus, film fabrication using gas pressure under 0.4Pa was not carried on. If the RF power is below 200Pa, the deposition rate of TiO₂ is too low thus can be negligible. When the RF sputtering power exceeds 200W, the deposition rate of TiO₂ will increase as the sputtering power increase. Similarly, the deposition rate of Ag will also increase as the DC sputtering power increase.2. TAT multilayer transparent conducting films were fabricated using room temperature magnetron sputtering. The effect of variance of Ag sputtering power and thickness on the transmittance and conductivity was studied. It is observed that as the Ag deposition rate increases, the continuity of the Ag layer also increases. Therefore, the TAT will have better conductivity and transmittance. When the Ag deposition current reaches 0.48A, the TAT multilayer will be with best performance. The TAT with different Ag thickness was deposited by sputtering current of 0.48A. When the thickness of Ag middle layer was 10nm, the average transmittance between 400 and 800nm of TAT reaches the highest value. When the Ag middle layer was 16nm, the TAT is of highest FOM of 15.97 × 10-2Ω-1 among all the TATs with Ag sputtering current of0.48A.3. The TAT multilayer films were used as transparent electrodes for the fabrication of P3HT:PCBM photodetectors. In addition, reference devices was also fabricated using commercially purchased ITO electrodes and same fabrication procedures as TAT based photodetectors. The photodetectors using TAT and ITO electrodes have similar performance in photocurrent.4. During the fabrication of TAT multilayer films, the Ag interlayer was oxidized to AgO_x by add some certain concentrations of oxygen. The effect of O₂ doping on the optical and electrical performance of TAOT multilayer films was studied. Firstly, similar as observed in the TAT multilayer film fabrication, it was observed that as interlayer sputtering current increases, the optical and electrical performance of TAOT was improved. However, oxygen doping of interlayer caused the decline of TAOT multilayer films on conductivity and optical transmittance, which was due to the reduction of interlayer continuity and the decline of AgO_x material itself.