| AVS 66th International Symposium & Exhibition | |
| 2D Materials | Tuesday Sessions |
| Session 2D+EM+MI+NS-TuA |
| Session: | Properties of 2D Materials including Electronic, Magnetic, Mechanical, Optical, and Thermal Properties II |
| Presenter: | Luca Camilli, Technical University of Denmark |
| Authors: | L. Camilli, Technical University of Denmark M. Galbiati, Technical University of Denmark L. Persichetti, Università degli Studi Roma Tre, Italy M. De Seta, Università degli Studi Roma Tre, Italy F. Fabbri, Italian Institute of Technology, Italy A. Scaparro, Università degli Studi Roma Tre, Italy A. Notargiacomo, Centro Nazionale di Ricerca, Italy V. Miseikis, Italian Institute of Technology, Italy C. Coletti, Italian Institute of Technology, Italy L. Di Gaspare, Università degli Studi Roma Tre, Italy |
| Correspondent: | Click to Email |
Unraveling the structural and electronic properties of the interface between graphene and conventional semiconductors is critical to enable novel graphene-based applications [1].
In this framework, the graphene/Ge(110) system has since last year received unprecedented attention [2-6]. Notably, graphene can be grown via chemical vapor deposition directly on the surface of germanium, similarly to the case of graphene grown on metals [7]. From a structural point of view, the graphene/Ge system is very dynamic, and the Ge surface has been shown by scanning tunneling microscopy (STM) studies to undergo a number of changes (i.e., reconstructions). However, the conclusions drawn in those studies do not always agree, probably also due to the strong dependence of the STM images on the applied voltage bias that makes comparison between different images rather difficult. In Ref. [6], for instance, the authors report three different surface reconstructions that are driven by thermal annealing, while the authors in Ref. [4] find only the unreconstructed surface and a (6x2) reconstruction, which again can reversibly change to unreconstructed surface after annealing at high temperature in hydrogen.
In this study, we aim at resolving the rich phase diagram of the Ge surface protected by graphene. We carry out annealing of the sample at different temperatures, and use a low-temperature STM to investigate the surface structure with atomic precision. At each stage, images at different applied biases are collected in order to allow a more straightforward comparison of the results.
Moreover, we perform electron energy loss spectroscopy (EELS) and scanning tunneling spectroscopy (STS) at temperature below 10 K to shed light on the electronic properties of the graphene/Ge interface, and to get more insights into their interaction.
Finally, we also show through a combination of STM and Raman spectroscopy that graphene can protect the germanium surface from oxidation even after continuous exposure to ambient conditions for more than 12 months, which is surprisingly a far more efficient protection than that offered by graphene on metals [8, 9].
References
[1] J.-H. Lee et al. Science 344, 286 (2014)
[2] G. Campbell et al. Physical Review Materials 2, 044004 (2018)
[3] J. Tesch et al. Nanoscale 10, 6068 (2018)
[4] D. Zhou et al. Journal of Physical Chemistry C 122, 21874 (2019)
[5] H.W. Kim et al. Journal of Physical Chemistry Letters 9, 7059 (2018)
[6] B. Kiraly et al. Applied Physics Letters 113, 213103 (2018)
[7] X. Li et al. Science 324, 5932 (2009)
[8]F. Zhou et al. ACS Nano 7, 6939 (2013)
[9] X. Zhang et al. Physical Chemistry Chemical Physics 18, 17081 (2016)