Electrical-field manipulated reversible switching between 1T and 2H phase in vertically aligned MoSe₂ via ion intercalation: a synapse-mimicking memristor

Ling Lee^1*, Chun-Shiu Chiang¹, Yu-Chuan Shih¹, Tzu-Yi Yang¹, Yu-Lun Chueh¹

¹Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Ling Lee, email:leeling0430@gmail.com

In this work, reversible resistance switchings were demonstrated in vertical aligned molybdenum diselenide (MoSe₂) thin films based on the electric-field induced phase change between the 1T and 2H geometry assisted by the metal ion intercalation. In horizontal Cu/MoSe₂/Au devices, this electric-field induced phase switching exhibits a great endurance of more than 100 cycles, high stability of more than 10,000 seconds under retention, and an on/off ratio of about 900%. Judging by the change of binding energy and the interlayer distance observed from the pseudo-operando scanning photoemission spectroscopy (SPEM) and transmission electron microscopy (TEM), once an applied positive bias was applied in a Cu/1T-MoSe₂/Au device, the external electric field drives active copper ions intercalated into vertical MoSe₂ lamellar structures via a CuSe_x intermediate layer, and introduces local distortions and atomic rearrangements from intrinsic 1T phase into 2H phase. On the contrary, the negative bias activates the RESET process and results in the phase change back to the 1T geometry. Since the 1T- and 2H-MoSe₂ exhibits metallic and semiconductive feature, respectively, the reversible phase change is considered as the origin of the resistance switching. Furthermore, based on the non-filament nature, multiple resistance levels together with an analog potentiation behavior was successfully achieved, allowing the device to emulate synaptic potentiation and depression behaviors.

Keywords: 1T-MoSe₂, memristor, synapse, Cu intercalation, phase change