Memristor with Perpendicular Exchange Bias

Tzu-Chuan Hsin¹, Yuan-Chieh Tseng^1*

¹Materials Science & Engineering, NYCU, Hsinchu, Taiwan

* Presenter:Yuan-Chieh Tseng, email:yctseng1978@nycu.edu.tw

Voltage control of exchange bias (EB) based on antiferromagnetic/ferromagnetic or multiferroic/ferromagnetic heterostructures is attracting increasing research interest due to its great potential in spintronics technology [1]. However, most of the oxide-based multiferroics (e.g. BiFeO3) rely on pulsed laser deposition as well as single-crystalline substrates, which limits the possibility of integrating them with today's semiconductor production lines. In this work, full voltage control of perpendicular EB by resistive switching (RS) at room temperature is demonstrated in a Si/SiO2/Ta/Pt/Co/NiO/HfO2/Ta/Pt voltage gate Hall device. We observed an exchange bias (HEB) of 40 Oe in the pristine device. By applying different voltages, we obtained low-resistance-state (LRS)/high-resistance-state (HRS) of the device accompanied by appearance/disappearance of HEB. The coupled HEB-RS was retained despite the removal of applied voltage, indicating the non-volatile nature of the device. The current-voltage (I-V) curve of the device showed unipolar RS behaviors, where the HRS/LRS was reset/set when the applied voltage exceeded 2.5/6.0 V. A mechanism of conductive filament (CF) is proposed to explain the voltage control of the concomitant EB and RS. When the device is set in the LRS, CFs are formed in the NiO and HfO2 layers, which break the NiO-Co exchange coupling, hence causing the disappearance of EB; while we reset the device in the HRS, CFs are ruptured near both Co-NiO and HfO2-top electrode interfaces, leading to the development of EB again. The mechanism has been validated by probing the oxygen states of the pristine/set/reset devices with x-ray photoelectron spectroscopy.

Keywords: memristor, exchange bias, perpendicular, conductive filament