Charged Impurity\nScattering and Electron–Electron\nInteractions in Large-Area Hydrogen Intercalated Bilayer Graphene

Intercalation is a promising technique to modify the\nstructural\nand electronic properties of 2D materials on the wafer scale for future\nelectronic device applications. Yet, few reports to date demonstrate\n2D intercalation as a viable technique on this scale. Spurred by recent\ndemonstrations of mm-scale sensors, we use hydrogen intercalated quasi-freestanding\nbilayer graphene (hQBG) grown on 6H-SiC(0001), to understand the electronic\nproperties of a large-area (16 mm<sup>2</sup>) device. To do this,\nwe first analyze Shubnikov–de Haas (SdH) oscillations and weak\nlocalization, permitting determination of the Fermi level, cyclotron\neffective mass, and quantum scattering time. Our transport results\nindicate that at low temperature, scattering in hQBG is dominated\nby charged impurities and electron–electron interactions. Using\nlow- temperature scanning tunneling microscopy and spectroscopy (STS),\nwe investigate the source of the charged impurities on the nm-scale\nvia observation of Friedel oscillations. Comparison to theory suggests\nthat the Friedel oscillations we observe are caused by hydrogen vacancies\nunderneath the hQBG. Furthermore, STS measurements demonstrate that\nhydrogen vacancies in the hQBG have an extremely localized effect\non the local density of states, such that the Fermi level of the hQBG\nis only affected directly above the location of the defect. Hence,\nwe find that the calculated Fermi level from SdH oscillations on the\nmillimeter scale agrees with the value measured locally on the nanometer\nscale with STS measurements.