Electric field mapping in 2D heterostructures using differential phase contrast

Gatan Instrument Used

The K3^® IS camera delivers simultaneous low-dose imaging via real-time electron counting, fast continuous data capture, and a large field of view. In a 4D STEM experiment, the STEMx^® system precisely synchronizes the speed of the scanning probe to the camera frame rate to enable high-speed data acquisition and eliminates the potential for data loss.

Background

Two-dimensional (2D) material heterostructures have produced a wide variety of features for the next generation of optoelectronic architectures and quantum information science. These heterostructures are composed of diverse 2D materials such as graphene, boron nitride (h-BN), and transition metal dichalcogenides. And their performance and functionalities largely result from the charge transport dynamics present at various 2D or contact interfaces.

Beyond information about a structure, 4D STEM can capture short- and long-range electrostatic fields and charge distributions by measuring the intensity fluctuations of the CBED patterns. The resultant differential phase contrast images depict the momentum transfer from the electron beam interactions with the sample’s electrostatic fields by measuring the deflection of an electron beam due to the field at each probe point. With a high-speed camera, these same methods can be applied in a dynamic framework where the sample is subjected to external biases to measure how the electrostatic profile evolves.