Studies on Magnetic Anisotropy of Molecular-Beam Epitaxial Grown Ni(111) and Photoluminance of ZnO Defect Characteristic

• Main Authors: Wu, Yan-Hui, 吳彥輝
• Other Authors: Chen, Jiunn
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/19717588240841475881

碩士 === 國立屏東大學 === 應用物理系碩士班 === 104 === The thesis is based on consign agreement between National Pingtung University and National Synchrotron Radiation Research Center. The molecular beam epitaxial film growth system were tested with Ni(111) at the very first stage in 2013. Modification of O2 inlet with a linear feed-through, 45o angle and 44mm to sample surface, additional degrees of freedom for oxide thin film grown process is introduced. That extend the process capability to NiO. Ni and NiO are prototypes of ferromagnetism (FM) and anti-ferromagnetism (AFM). They are typical model system for Stoner-Wohlfarth theory and Kramers-Anderson superexchange theory. Following the epitaxial Ni(111) grown on Al2O3(0001) process, further film characterization, i.e., orientation relationship between film and substrate, temperature dependence magnetic anisotropy, were conducted. To improve the limit and the stability, the refurbishing of the vacuum heater is an important subject of present thesis. Detail procedure and performence testing is presented. Heating capability has improved from 450oC to 700oC; stability improves to within 5 minutes. Substrate temperature (S.T.) dependence (RT, 250oC, 450oC, 650oC) structural as well as magnetic characterization were conducted with various film thickness (5-80nm) and growth rate (3, 6, 11, 22 Å/min). Vibrating Sample Magnetometer (VSM) and High Resolution X-ray Diffraction (HRXRD) were put into used for magnetic and structural characterization, respectively; Scanning Probe Microscopy (SPM) to examine film surface morphology. We have found the grown rate has the less influence on pre-mentioned properties, but the substrate temperature. The results suggest in-plane easy axis at lower S.T. (RT, 250oC, 450oC), while that rotate for those with higher S.T. Remanence ratio were found to be significantly correlated with S.T. and film thickness, and thus, the grain size. In addition, secondary phase Ni(200) exhibited for lower S.T. were found to be related to dual magnetic phase observed in magnetization curve.