Scanning Kelvin Probe Microscopy Study of Magnetic Topological Insulators Mn Bi₂Te₄（Bi₂Te₃）_n

The intrinsic magnetic topological insulators MnBi₂Te₄(Bi₂Te₃)_n have attracted much attention due to its Quantum Anomalous Hall effect.The series of materials are van der Waals heterostructures formed by stacking Mn Bi₂Te₄(MBT layer) and Bi₂Te₃(BT layer).Because they are easy to exfoliate,people turn interest in bulk materials to two-dimensional films,and found that these parity characteristics may affect the magnetic topological properties.The method of judging the type of cleavage surface under the two-dimensional limit is not known,which hinders the study of two-dimensional films.In this paper,the surface electrical properties of different cleavage layers of MnBi₂Te₄(Bi₂Te₃)_n system have been studied at by using Scanning Kelvin probe microscopy (SKPM).The type of cleavage surface was judged by comparing its SKPM image with the morphological image.The stability of the cleavage surface and the influence of the potential of the materials on magnetic imaging have been further studied.Our research shows that the surface potential of BT layer is higher than MBT layer,and the type of cleavage surface in Mn Bi₂Te₄ can be judged by SKPM image.The surface potentials of different BT layers in Mn Bi₆Te₁₀and MnBi₈Te₁₃ are consistent,which can be judged in combination with SKPM image and morphological image.We found that the surface potential of BT layer and MBT layer increases and the potential difference between BT layer and MBT layer decreases when the materials are placed in the atmospheric environment for a long time.As a method of judging the type of cleavage type,SKPM not only provides help for the study of the magnetic topological properties of thin-layer materials,but also provides a new method and idea for the study of the surface electrical properties of other van der Waals heterostructures.