Atomic processing of two-dimensional amorphous carbon

Abstract

Two-dimensional amorphous carbon (2DAC) materials possess characteristics such as high conductivity, high flexibility, and chemical stability, making them promising for applications in electronics, sensors, catalysts, superconductors, energy storage, and energy conversion. However, it is still a challenge to directly synthesize 2DAC till now. Meanwhile, many controversies exist in their formation process and structure. Therefore, this article utilizes a top-down etching method to prepare 2DAC in environmental transmission electron microscope (ETEM). By employing electron beam irradiation combined with heating at 650°C in an oxygen atmosphere (0.01 mbar), controllable fabrication of 2DAC is achieved. In this process, the raw diamond sheet first transforms into graphite, and as the reaction goes on, the amount of graphite increases, eventually transitioning into 2DAC. First-principles calculations indicate that it is an energy-favorable process from diamond to graphite. Although there is an energy barrier for graphite-to-amorphous carbon transition, electron beam irradiation induces numerous defects that can overcome this barrier. This method not only fabricates 2DAC with atomic precision but also provides in-situ analysis of its formation process. The research findings contribute to a fundamental understanding of the formation process of 2DAC and offer new insights for the preparation of 2D ultrathin amorphous materials.