Optimization of Epitaxial Graphene Growth on SiC for Quantum Hall Metrology

The performance of graphene-based electronic devices; specifically in metrological applications, depends strongly on the quality and homogeneity of the underlying graphene layer. An inherent so-called step bunching, and graphene bilayer formation are two major challenges regarding graphene fabrication via epitaxial graphene growth on SiC. These problems can be effectively overcome by a technique so-called polymer-assisted sublimation growth (PASG), thereby the sublimation growth is supported by predeposited polymer adsorbate (as additional carbon source) on the SiC substrate. By applying the PASG, successful growth optimization, and taking into account a less-regarded influence of argon flow rate ultra-smooth and homogenous types of epitaxial graphene on SiC: bilayer-free monolayer graphene, quasi-freestanding monolayer and bilayer (QFMLG and QFBLG), and graphene-free buffer layer are achieved. Accordingly, the resistance anisotropy of epitaxial graphene was reduced down to 2 percent.

Furthermore, the growth optimization yields a precise graphene thickness control and graphene fabrication on different SiC stacking terminations, so that providing an excellent platform for studying the mesoscopic interaction between the inequivalent SiC terminations and the top carbon layers. Accordingly, evidence of doping modulation domains entangled with the SiC stacking terminations are identified and described in a step-flow model consistent with several experimental measurements. This study also reveals important information about the strain and dislocation boundary networks in epitaxial graphene.