RF magnetron sputter deposition of BiCuSeO epitaxial films

• Main Authors: Mei-ChingHuang, 黃美靜
• Other Authors: Xiao-Ding Qi
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/sxa5ep

碩士 === 國立成功大學 === 材料科學及工程學系 === 106 === In this study, we attempted to grow epitaxial BiCuSeO (BCSO) films on (110) and (001) SrTiO3 (STO) substrates as the bottom electrode for the growth of multiferroic BiFeO3 (BFO) films. In our previous attempts, BCSO films of two in-plane orientations were obtained owing to the rapid deposition rate. So, in this work, we used two methods to reduce the rate. One was placing a stainless steel mesh above the substrate in order to scatter the sputtered atoms. Another one was controlling shutter opening time to adjust deposition rate. The films grown with the mesh were mainly (001) orientated but contained some (110) orientation and yet the film surface was rough. The films grown with the shutter had a unique (001) texture when the substrate temperature was 400 C and the shutter opening and closing times were 1 and 30 seconds, respectively. High-resolution X-ray diffraction (HRXRD) confirmed that the (001) oriented films were in-plane aligned as well, i.e. the grown BCSO films were epitaxial. Although bulk BCSO had larger a/b axes than STO, HRXRD showed that the a/b axes of BCSO films were stretched rather than compressed. Similarly, the c-axis of films was slightly shortened instead of being elongated. This was probably related to oxygen deficiency in the films. Cross-sectional transmission electron microscopy confirmed the epitaxial relationship between BCSO film and STO substrate. The resistivity of films measured at room temperature was 2.02×10-2 Ohmcm, which was good enough as the electrode. It was found that (001) BCSO epitaxial films could also be grown on the (110) oriented STO substrates. The BCSO films on (110) STO could be grown at very high rate, but only at the substrate temperature of 500 C. The resistivity of the BCSO epitaxial films on (110) STO was higher (9.55×10-3 Ohmcm). Preliminary attempts were made to grow epitaxial BFO films on BCSO. Polycrystalline BFO films of a pure phase were obtained, but the epitaxial growth has yet to be achieved.