Event Date
Manipulating Ferroic Responses in 2D Materials:
Layered van der Waals materials have enabled novel electrical, optical and mechanical properties that are not observable in conventional 3-dimensional materials. 2D ferroic (ferromagnetic, ferroelectric) materials are bringing us new opportunities in controlling material response to external stimuli and enabling novel device applications such as memories.
We use the MX (M= Sn, Ge; X=S, Se) material family to demonstrate a 2D ferroelectric platform with four ground states. We realized AA stacking of 2D SnSe layers, which preserves the broken inversion symmetry of the crystal structure, thus its ferroelectricity. The co-existence of in-plane and out-of-plane polarizations in different thicknesses of SnSe sheets is observed. More importantly, the switching voltage of the SnSe sheets scales down with the thickness and approaches sub-0.3V regime, offering great potential for low-power device applications.
Besides the ferroelectrics, we also developed a novel approach to achieve diluted magnetic oxides at the 2D limit. By intercalating zinc ions into the van der Waals gaps between graphene oxide template layers, we created monolayers and bilayers of ZnO in the van der Waals phase. It also allows us to introduce magnetic dopants in ZnO sheets, such as Co atoms, enabling a novel ferromagnetic phase at room temperature. Such materials offer novel opportunities for spintronic and memory device applications.