Imaging the Electronic Structure of Strained Epitaxial Monolayer Graphene

Epitaxial graphene (EG) has applications in quantum Hall resistance standards, chemical and biochemical sensing. Here, using a photoemission electron microscope (PEEM), we image EG topography in real space and measure the electronic structure of monolayer EG regions with micrometer-scale angle resolved photoemission (μ-ARPES). We detect characteristic electronic features of graphene such as the Dirac points and the π-band. On different regions of the sample which look topographically similar, we observe electronic structure including  the electronic flat band. We performed Raman spectroscopy on the same regions that were analyzed by PEEM, and we estimated a significant amount of compressive strain (~1.2%) by comparing the 2D and G positions using a vector decomposition model [1]. It has been proposed by others that the compressive strain could modify the electronic band structure in monolayer graphene [2, 3].   

 

[1] J. E. Lee et al., Nat. Commun. 3:1024 doi: 10.1038/ncomms2022 (2012).

[2] J. Mao et al., Nature 584, 215 – 220 (2020).

[3] S. P. Milovanovic et al., Phys. Rev. B 102, 245427 (2020).