E-Beam-Mediated Rapid Synthesis of Graphite/Diamond Heterojunctions via (111) Facet-Dirven Global Graphitization

Carbon, a highly versatile element, forms allotropes (diamond, graphite, graphene, etc.) with distinct physicochemical properties. Traditional carbon-based heterojunctions suffer from interface limitations, while in-situ grown diamond/graphite heterojunctions via diamond-to-graphite transformation offer superior interfacial bonding, but their transformation mechanism remains unclear. Herein, we fabricate graphite/diamond heterojunctions by electron beam irradiation of intrinsic polycrystalline and single-crystal diamond with different surface crystallographic orientations, specifically (111), (110), and (100) facets. The heterojunctions are systematically characterized using SEM, AFM, Raman spectroscopy, and HRTEM. Based on these results, we uncover the phase transformation tendencies of different diamond crystallographic planes and clarify the driving mechanism of the diamond-to-graphite transition. Locally observed nanoscale transition regions, characterized by coexisting diffraction features, provide evidence against interface-initiated nucleation and growth. We suggest a more plausible "global graphitization" pathway, in which partial diamond domains undergo collective structural rearrangement to form graphite, as an alternative to the classical nucleation-and-growth model. This work fills the gap in carbon solid-state phase transition theory, provides theoretical support for low-dimensional carbon heterojunction interfacial engineering, and advances precise/controllable heterojunction design. It holds significant value for electronic devices, energy storage, and catalysis.