Direct Probe of Voltage-induced Interfacial Effects on the Electronic and Spin Transport Property of the Fe/ZnO Spintronic Device

• Main Authors: Luo, Shao-Hua, 羅紹驊
• Other Authors: Tseng, Yuan-Chieh
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/66540493884822583567

碩士 === 國立交通大學 === 材料科學與工程學系所 === 105 === This work demonstrates the interface oxidation control in relation to spin-transport properties of a Fe/ZnO heterostructure device, with the use of a unique x-ray setup that is capable of performing in-situ x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) with electrical control. The heterostructure with oxidized Fe was initially prepared, yet the Fe chemical state was modified by applying voltage on a Hall-bar based Fe/ZnO device in an ultra-high vacuum condition (<10-10 torr). In-situ XAS shows that the Fe layer underwent an oxidized (0 V~70 V) to metallic transition (70 V~120 V) with increasing applied voltage. A voltage-induced enhancement of coercivity (Hc) was also observed by in-situ XMCD. This suggests the modifications of Fe’s spin-electronic state as a result of voltage-driven reduction of the Fe state specifically occurring at Fe/ZnO interface. Element-specific anisotropy magnetoresistance (AMR) measurement was operated on the Fe layer by fixing photon energy at Fe L3 absorption edge upon magnetic field reversal. The increase of switching field is consistent with Hc enhancement, which indicates a different reversal mechanism of the Fe layer enabled by applied voltage. This work enables a straightforward detection of interface-state in conjunction with spin-transport and magnetic-reversal properties of the versatile ferromagnet-semiconductor system, by taking advantage of x-ray’s element-specificity in combination with electrical control characterizations.