Step-edge-induced resistance anisotropy in quasi-free-standing bilayer chemical vapor deposition graphene on SiC

Abstract

The transport properties of quasi-free-standing (QFS) bilayer graphene on SiC depend on a range of scattering mechanisms. Most of them are isotropic in nature. However, the SiC substrate morphology marked by a distinctive pattern of the terraces gives rise to an anisotropy in graphene's sheet resistance, which may be considered an additional scattering mechanism. At a technological level, the growth-preceding in situ etching of the SiC surface promotes step bunching which results in macro steps ∼ 10? nm in height. In this report, we study the qualitative and quantitative effects of SiC steps edges on the resistance of epitaxial graphene grown by chemical vapor deposition. We experimentally determine the value of step edge resistivity in hydrogen-intercalated QFS-bilayer graphene to be ∼ 190? Ωμ m for step height hS? =? 10? nm and provide proof that it cannot originate from mechanical deformation of graphene but is likely to arise from lowered carrier concentration in the step area. Our results are confronted with the previously reported values of the step edge resistivity in monolayer graphene over SiC atomic steps. In our analysis, we focus on large-scale, statistical properties to foster the scalable technology of industrial graphene for electronics and sensor applications. © 2014 AIP Publishing LLC

Statistics of epitaxial graphene for Hall effect sensors

“…The resultant is α ranging from 0° to 180° with the terraces running at an acute angle (α<90°), vertically (α=90°) or at an obtuse angle (90°<α<180°) calculated from the level. This method is slightly different than the one adopted in [16]. …”

“…It had been observed that the step edges are more resistive than the terraces and it is very possible that the augmented resistivity is a result of a lowered carrier concentration within the step edge area; however, this mechanism could be further deepened by a possible scattering mechanism localized in the vicinity of the step edges [16]. Each of the 140 4H-SiC(0001) and 60 6H-SiC (0001) and C should occur.…”

“…Each of the 140 4H-SiC(0001) and 60 6H-SiC (0001) and C should occur. Since epitaxial graphene on SiC exhibits pronounced step-edge-induced anisotropy [16], the offset voltage U AC was analyzed as a function of the angle α to illustrate possible angle-dependence of the offset voltage.…”

“…Fig.2 illustrates a representative map of the 2D band width within the terrace and step edge area. A detailed Raman discussion was presented in [16]. The room- [21].…”

“…Special attention is paid to Hall-effect-based magnetic field detection. A method for minimizing the offset voltage which is enhanced by the step-edge-induced resistance anisotropy in epitaxial graphene on SiC [16] is presented.…”