Transmission-Electron-Microscopy-Generated Atomic Defects in Two-Dimensional Nanosheets and Their Integration in Devices for Electronic and Optical Sensing

For electronic and optical applications of two-dimensional (2D) materials and their vertical heterostructures, it is important to know the positions, densities, and atomic structures of crystallographic defects. Thus, to understand the role of these well-defined defects on the properties of 2D heterostructure devices, it is desirable to combine device measurements with atomically resolved transmission electron microscopy (TEM) experiments. Here, the electron beam is used not only to image atomic defects but also to create and manipulate them. However, TEM poses special requirements to sample preparation because it needs freestanding samples. Our presented generic sample platform enables TEM imaging of freestanding 2D materials, followed by experiments on the same sample area placed on an arbitrary substrate or embedded into a heterostructure device. A sacrificial copper layer and a hydrophobic polystyrene film enable the transfer of a strongly adhered 2D material flake from a TEM grid to the substrate. Proof-of-principle experiments show that signatures of electron-beam-induced defects can be measured in electric tunneling measurements and photoluminescence. Our transfer procedure works reliably for monolayer and few-layer transition-metal dichalcogenides such as MoS2, MoSe2, WSe2, MoTe2, hBN, and graphene. It can also be suitable for the assembly of defect-based sensors and photon sources.