Top‐Down Fabrication of Atomic Patterns in Twisted Bilayer Graphene

Abstract

Atomic‐scale engineering typically involves bottom‐up approaches, leveraging parameters such as temperature, partial pressures, and chemical affinity to promote spontaneous arrangement of atoms. These parameters are applied globally, resulting in atomic‐scale features scattered probabilistically throughout the material. In a top‐down approach, different regions of the material are exposed to different parameters, resulting in structural changes varying on the scale of the resolution. In this work, the application of global and local parameters is combined in an aberration‐corrected scanning transmission electron microscope (STEM) to demonstrate atomic‐scale precision patterning of atoms in twisted bilayer graphene. The focused electron beam is used to define attachment points for foreign atoms through the controlled ejection of carbon atoms from the graphene lattice. The sample environment is staged with nearby source materials such that the sample temperature can induce migration of the source atoms across the sample surface. Under these conditions, the electron‐beam (top‐down) enables carbon atoms in the graphene to be replaced spontaneously by diffusing adatoms (bottom‐up). Using image‐based feedback control, arbitrary patterns of atoms and atom clusters are attached to the twisted bilayer graphene with limited human interaction. The role of substrate temperature on adatom and vacancy diffusion is explored by first‐principles simulations.

The Synthescope: A Vision for Combining Synthesis with Atomic Fabrication

“…c) Long-range dopant insertion facilitated by evaporating nanoparticles on the graphene surface, performed at elevated temperatures. [36] d) Removal of the source material from the sample surface will enable independent control over the source evaporation rate and the substrate temperature. Additionally, this approach preserves the cleanliness of the sample surface.…”

“…Such a strategy was presented in Figure 2 and is schematically represented in Figure 1c. [36] In this approach, the sample is heated until the source material, in the form of nanoparticles sitting on the sample surface, begins to atomize and diffuse across the substrate. The substrate temperature also plays a role in promoting surface diffusion.…”

A Platform for Atomic Fabrication and In Situ Synthesis in a Scanning Transmission Electron Microscope

“…In the last few years, the scanning transmission electron microscope (STEM) has been reconceptualized, transitioning from characterization-only to a characterization-plus-manipulation platform. [2][3][4][5] Numerous demonstrations have ranged from the creation of nanowires [6,7] to 1D chains of atoms, [8][9][10][11][12] sculpting, [13][14][15][16][17] molecule-by-molecule deposition, [18] the movement of single atoms, [19][20][21][22][23] the attachment of atoms, [24][25][26][27][28] and atomic patterning [29] and writing. [30] At the same time, feedback-controlled methods for material transformation, manipulation, and beam control in a STEM have also become increasingly refined, now leveraging artificial-intelligence (AI) based decision making.…”

“…Reproduced with permission. [29] Copyright 2023, Wiley VCH. g,h) direct-writing of Sn atoms in graphene.…”

“…Importantly, this differs from STEM-based EBID [18,51] in that it is not confined to the dissociation of a precursor gas but also includes working with purified precursor materials. [29,30] This would enable multi-component synthesis processes combined with atomic-scale tailoring, real-time feedback control, and AI decision making.…”