Peeling off Nanometer-Thick Ferromagnetic Layers and Their van der Waals Heterostructures

The recent discovery of 2D van der Waals (vdWs) magnetic crystals provides an ideal platform for fundamental understanding of 2D magnetism, as well as the applications of low-power spintronic devices. One can integrate 2D magnetic materials into vdWs heterostructures with engineered properties, and also manipulate the magnetism via electrostatic gating. However, due to their instability, the handing of 2D magnetic materials can only be carried out under the help of encapsulation with other 2D materials (such as hexagonal boron nitride (hBN)) in a glove box, which is the biggest barrier toward its practical applications. Here, an approach about peeling-off and transfer of 2D ferromagnetic (Ga,Mn)As layers with thickness of approximate to 10-20 nm grown by the molecular beam epitaxy under ambient conditions is introduced. Transmission electron microscopy characterizations confirm the single-crystalline nature of the lifted-off (Ga,Mn)As. Superconducting quantum interference device measurements demonstrate that the lifted-off (Ga,Mn)As maintains its ferromagnetism. Using vdWs heterostructure assembly, technique hBN/(Ga,Mn)As top-gate Hall device and p-(Ga,Mn)As/n-MoS2 heterojunction diode are fabricated. The electrical transport measurements demonstrate the ferromagnetic nature and gate tunable magnetoresistance of the lifted-off (Ga,Mn)As layer. This approach makes it possible to significantly expand the range of 2D ferromagnetic materials and their vdWs heterostructures.