Solid State at Atomic Level - Using High-Energy Electrons to Sculpture the "Plenty of Room at the Bottom"
Atomic Tailoring — creating and synthesizing solid structures atom-by-atom — was introduced by Richard Feynman in 1959 at Caltech in his famous speech, "Plenty of Room at the Bottom". The birth of Atomic Tailoring is symbolized by the maneuvering of atoms using scanning tunneling microscope (STM) in 1987. Almost at the same time, the introduction of another atom control technique, optical tweezer, heralded the emergence of Ultracold Atomic Physics. However, for decades, the requirement of using extreme conditions (i.e., low temperature and laser) to stabilize the structures limits their integration into broader systems.In this talk, I'm going to introduce an emerging Atomic Tailoring method which utilizes the focused electron beam inside transmission electron microscopes (TEM). With the advent of aberration correctors, electron beam can be focused to be smaller than 1 angstrom with the precision of single atoms. The electrons can transfer enough energy that is able to move or displace atoms in the crystal. This process is usually called "radiation damage" when undesired, but with a control of the electron beam condition, it can be tailored to be a powerful tool for controlling the dynamics of atoms or creating atomic defects which are stable in ambient conditions.This talk will be divided into four sections: First section is about how we control the dopant dynamics in graphene and build up a basic theory called Primary Knock-on Space for describing the cross sections of different atomic dynamics. Second section is a brief introduction on how we synthesize doped 2D materials that are used in Atomic Tailoring. In the third section, I will present our discovery of the record-low contact resistance between Bi and 2D semiconductors which facilitates the deployment of single-atom devices. The last section involves our latest discovery of the activation of defect emission of hBN through twisting the layers.
Cong Su's work focuses on modifying and controlling atomic-level structures in two-dimensional materials, including doping in the fabrication process, and modification using high energy electron beam after materials are made. Cong Su received his Ph.D. degree in Nuclear Science and Engineering from MIT in 2019, and a Bachelor's in physics from Yuanpei College, Peking University in 2013.