Two-dimensional (2D) materials are layered materials that are only a few atoms thick. Examples include graphene and monolayer transition metal dichalcogenides. These 2D materials have very different properties from their bulk counterparts and can be integrated into ultrathin and flexible nanodevices. Here is an STM image of a defect in graphene:
Scanning Tunneling Microscopy
Scanning tunneling microscopy (STM) is a powerful tool for characterizing surfaces with atomic-scale resolution. By applying a bias between a conducting tip and surface, electrons are extracted from or injected into the surface via quantum tunneling. Measuring the tunneling current provides energy-resolved electronic structure information about the surface. Additionally, STM images can be Fourier transformed to obtain momentum-space data. Below is a picture of an STM tip, together with a piezoelectric motor that moves the tip.