Graphite to diamond transition induced by photoelectric absorption of ultraviolet photons

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The phase transition from graphite to diamond is an appealing object of study because of many fundamental and also, practical reasons. The out-of-plane distortions required for the transition are a good tool to understand the collective behaviour of layered materials (graphene, graphite) and the van der Waals forces. As today, two basic processes have been successfully tested to drive this transition: strong shocks and high energy femtolaser excitation. They induce it by increasing either pressure or temperature on graphite. In this work, we report a third method consisting in the irradiation of graphite with ultraviolet photons of energies above 4.4 eV. We show high resolution electron microscopy images of pyrolytic carbon evidencing the dislocation of the superficial graphitic layers after irradiation and the formation of crystallite islands within them. Electron energy loss spectroscopy of the islands show that the sp(2) to sp(3) hybridation transition is a surface effect. High sensitivity X-ray diffraction experiments and Raman spectroscopy confirm the formation of diamond within the islands.
©2021 The Author(s) We are indebted to Dr. Santiago Sanchez-Cortes from the Instituto de Estructura de la Materia (Consejo Superior de Investigaciones Cientificas, CSIC-Spain) who kindly offered his lab and assistance to obtain the Raman spectra. We thank Dr. Jacob P.C. Ruff from the Cornell High Energy Synchrotron Source (CHESS) for his assistance with CHESS data. This work is based upon research conducted at the Spanish National Centre for Electron Microscopy and at the Cornell High Energy Synchrotron Source (CHESS) which is supported by the National Science Foundation under award DMR-1332208. Additional support was provided by the Ministry of Science and Education of Spain and the Natural Sciences and Engineering Research Council (NSERC) of Canada, the Canada Foundation for Innovation (CFI) and the Ontario Ministry of Research, Science and Innovation.