Clean contacts for spintronics and ferroelectric memory with 2D materials

Spintronic and ferroelectric devices based on atomically thin 2D materials are promising for high-density and low-power non-volatile memory for future computing. A key challenge is to fabricate such devices with ideal interfaces using foundry compatible methods while maintaining high performance.¹ In this talk, I will discuss how cobalt based clean ferromagnetic van der Waals (vdW) contacts can be deposited on graphene to enable room temperature spin-injection, resulting in magnetoresistance an order of magnitude higher than defective contacts with pure cobalt. By leveraging spin tunneling across the vdW gap between the ferromagnet and graphene, we eliminate the need for ultrathin dielectric tunnel barriers, which are typically difficult to fabricate reproducibly on dangling-bond-free 2D surfaces. I will also discuss how similar strategies improve the performance of ferroelectric diodes (FeDs) based on vdW ferroelectrics, achieving electroresistance around 10⁶, rectification ratios above 2500 at low read/write voltages of 0.5/2V. The improved behaviour arises from suppression of interface pinning, enabling effective modulation of the average barrier height upon polarisation switching. In addition, the stabilisation of intermediate net polarisation states leads to multi-state data retention at room temperature. Combined with its two-terminal self-selecting design, FeDs based on vdW heterostructures provide opportunities for high-density compute-in-memory hardware.

References

1. Yan Wang, Soumya Sarkar, Han Yan, Manish Chhowalla, “Perspectives on critical challenges in two-dimensional transition metal dichalcogenides for electronics” Nature Electronics, 2024, 7 (8), 638-645.
2. Soumya Sarkar, Saeyoung Oh, Peter J. Newton, Yang Li, Han Yan, Hu Young Jeong, Yan Wang, Manish Chhowalla “Spin injection in graphene using ferromagnetic indium-cobalt van der Waals contacts” Nature Electronics, 2025, 1-7.
3. Soumya Sarkar, Zirun Han, Maheera Abdul Ghani, Nives Strkalj, Jung Ho Kim, Yan Wang, Deep Jariwala, Manish Chhowalla “Multistate ferroelectric diodes with high electroresistance based on van der Waals heterostructures” Nano Letters, 2024, 24 (42), 13232-13237.
4. Soumya Sarkar, Xiwen Liu, Deep Jariwala, “Can a ferroelectric diode be a selector-less, universal, non-volatile memory?” MRS Energy & Sustainability, 2025.