Journal
APPLIED SURFACE SCIENCE
Volume 602, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.apsusc.2022.154291
Keywords
Graphene; Germanium; Chemical vapor deposition; Scanning tunneling microscopy; X-ray photoemission spectroscopy; Raman spectroscopy
Categories
Funding
- EU [730872, 785219]
- Lazio Innova (Regione Lazio, Italy) [A0375-2020-36566]
- EPSRC [EP/M508007/1, EP/P005152/1]
- NPL
- Villum Young Investigator Program [19130]
- EUROFEL project (RoadMap Esfri)
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The quality of graphene, obtained through Raman spectroscopy, has been correlated with the structural changes occurring at the graphene/germanium interface during in-vacuum thermal annealing. It was found that graphene becomes significantly defective at 650 degrees C due to the release of trapped H-2 gas. Interestingly, a complete self-healing process was observed in graphene upon annealing at 800 degrees C.
Graphene quality indicators obtained by Raman spectroscopy have been correlated to the structural changes of the graphene/germanium interface as a function of in-vacuum thermal annealing. Specifically, it was found that graphene becomes markedly defective at 650 degrees C. By combining scanning tunneling microscopy, X-ray photo-electron spectroscopy and near edge X-ray absorption fine structure spectroscopy, we concluded that these de-fects are due to the release of H-2 gas trapped at the graphene/germanium interface. The H-2 gas was produced following the transition from the as-grown hydrogen-termination of the Ge(1 1 0) surface to the emergence of surface reconstructions in the substrate. Interestingly, a complete self-healing process was observed in graphene upon annealing at 800 degrees C. The identified subtle interplay between the microscopic changes occurring at the graphene/germanium interface and graphene's defect density is integral to advancing the understanding of graphene growth directly on semiconductor substrates, controlled 2D-3D heterogeneous materials interfacing and integrated fabrication technology.
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