Voltage-induced Interface Reconstruction and Electrical Instability of the Ferromagnet-Semiconductor Device.
Using x-ray magnetic spectroscopy with in-situ electrical characterizations, we investigated the effects of external voltage on the spin-electronic and transport properties at the interface of a Fe/ZnO device. Layer-, element-, and spin-resolved information of the device was obtained by cross-tuning of the x-ray mode and photon energy, when voltage was applied. At the early stage of the operation, the device exhibited a low-resistance state featuring robust Fe-O bonds. However, the Fe-O bonds were broken with increasing voltage. Breaking of the Fe-O bonds caused the formation of oxygen vacancies and resulted in a high-resistance state. Such interface reconstruction was coupled to a charge-transfer effect via Fe-O hybridization, which suppressed/enhanced the magnetization/coercivity of Fe electronically. Nevertheless, the interface became stabilized with the metallic phase if the device was continuously polarized. During this stage, the spin-polarization of Fe was enhanced whereas the coercivity was lowered by voltage, but changes of both characteristics were reversible. This stage is desirable for spintronic device applications, owing to a different voltage-induced electronic transition compared to the first stage. The study enabled a straightforward detection of the spin-electronic state at the ferromagnet-semiconductor interface in relation to the transport and reversal properties during operation process of the device.
Department of Materials Science & Engineering, National Chiao Tung University, Hsinchu, Taiwan.
Shu-Jui
SJ
Chang
Department of Physics, National Taiwan Normal University, Taipei, Taiwan.
Po-Chun
PC
Chang
Department of Physics, National Taiwan Normal University, Taipei, Taiwan.
Wen-Chin
WC
Lin
Department of Materials Science & Engineering, National Chiao Tung University, Hsinchu, Taiwan.
Shao-Hua
SH
Lo
Institute of Physics, Academia Sinica, Taipei, 30010, R.O.C., Taiwan.
Liang-Chun
LC
Chang
Institute of Physics, Academia Sinica, Taipei, 30010, R.O.C., Taiwan.
Shang-Fan
SF
Lee
Department of Materials Science & Engineering, National Chiao Tung University, Hsinchu, Taiwan. yctseng21@mail.nctu.edu.tw.
Yuan-Chieh
YC
Tseng