Preparation of transparent conducting oxide thin films and their p-n junction characteristics by dc magnetron sputtering processes

• Main Authors: Chun Lung Chu, 朱俊隆
• Other Authors: H. C. Lu
• Format: Others
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/66358302110596583386

博士 === 長庚大學 === 化工與材料工程學系 === 99 === The objectives of this dissertation study were to prepare various n-type and p-type transparent conductive oxide (TCO) thin films using direct current (dc) magnetron sputtering and to combine these n-type and p-type TCO thin films to form TCO thin film p-n junction diodes. In addition, the effects of different TCO material combinations, device designs, and sputtering processing conditions on the characteristics of TCO thin film p-n junction diodes also were investigated. This study was divided into three main portions: 1. Fabrication of Cu2O thin films by dc reactive magnetron sputtering. 2. Fabrication of AZO thin films by dc magnetron sputtering. 3. Investigation of the effects of different TCO material combinations, device designs, and sputtering processing conditions on the characteristics of TCO thin film p-n junction diodes. From the experimental results, it was found that the electrical, optical, microstructures and crystallographic properties of Cu2O and AZO thin films were sensitive to the deposition conditions, such as working pressure, selection of reactive gas, partial pressure of reactive gas, deposition time, substrate rotation, substrate temperature, and dc plasma power, etc. Single-phase p-type Cu2O thin films with the best characteristics of electrical resisitivity of 11.8 ohm-cm, hole concentration of +9.29×1017 cm-3, Hall mobility of 0.65 cm2/V Sec, average optical transmittance of 41.36 %, and optical band gap of 2.38 eV were deposited by dc reactive magnetron sputtering under the conditions of a working pressure of 6.3×10-3 torr, Ar flow rate of 14 sccm, O2 flow rate of 6 sccm, substrate temperature of 200 oC, substrate rotation of 12 rpm, dc power of 60 W, deposition time of 3.5 min, and working distance of 65 mm. Single-phase n-type AZO thin films with the best characteristics of electrical resisitivity of 3.14×10-4 ohm-cm, electrin concentration of -2.89×1021 cm-3, Hall mobility of 7.03 cm2/V Sec, average optical transmittance of 91.77 %, and optical band gap of 3.46 eV were deposited by dc reactive magnetron sputtering under the conditions of a working pressure of 2.5×10-3 torr, Ar flow rate of 10 sccm, substrate temperature of 250 oC, substrate rotation of 12 rpm, dc power of 60 W, deposition time of 10 min, and working distance of 65 mm. The performance of TCO thin film p-n junction diodes was found to be influenced by the properties of the p- or n-type TCO thin films, device designs, and device fabrication conditions. In particular, the properties of the p-type TCO thin films were very sensitive to post deposition processing conditions. In confirmation of this study, the efficiency of 0.003% and average optical transmittance of 29.84% using AM1.5G solar illumination were obtained in the Glass/ n-AZO/ i-ZnO/ p-Cu2O heterojunction solar cell fabricated by magnetron sputtering. Keywords: solar cell, TCO, dc magnetron sputtering, resistivity, transmittance, and optical band gap energy.