Minimum Resistance Anisotropy of Epitaxial Graphene on SiC

Abstract

We report on electronic transport measurements in rotational square probe configuration in combination with scanning tunneling potentiometry of epitaxial graphene monolayers which were fabricated by polymer-assisted sublimation growth on SiC substrates. The absence of bilayer graphene on the ultralow step edges of below 0.75 nm scrutinized by atomic force microscopy and scanning tunneling microscopy result in a not yet observed resistance isotropy of graphene on 4H- and 6H-SiC(0001) substrates as low as 2%. We combine microscopic electronic properties with nanoscale transport experiments and thereby disentangle the underlying microscopic scattering mechanism to explain the remaining resistance anisotropy. Eventually, this can be entirely attributed to the resistance and the number of substrate steps which induce local scattering. Thereby, our data represent the ultimate limit for resistance isotropy of epitaxial graphene on SiC for the given miscut of the substrate.

Ballistic tracks in graphene nanoribbons

“…Epitaxial graphene layers hold great potential for advanced interface engineering. The homogeneity of large graphene layers grown on SiC(0001) make them even suitable for quantum Hall metrology applications 1 – 4 . The selective growth of graphene by sublimation on the sidewalls of SiC mesa structures produces graphene nanoribbons (GNR) of excellent quality 5 – 12 .…”

Substrate induced nanoscale resistance variation in epitaxial graphene

“…Although the 6H-SiC(0001) exhibits six different (crystal) terminations (labeled as S1, S2, S3 and S1 * , S2 * , S3 * [47] in Supplementary Fig. 15), only 4 out of the 6 possible 6H-SiC terminations are found [28], because the terraces S1/S1* have a higher decomposition velocity [34,48] compared to the other terraces and therefore disappear during the growth process. We label the graphene terraces according to the substrate terminations as S2/S2* and S3/S3*.…”

“…The idea of this method is to support the growth process with an external carbon source. A polymer is deposited on the substrate using liquid phase deposition before high-temperature sublimation growth is initialized [9,10,28]. Samples prepared with this method are almost defectand bilayer-free and exhibit shallow step heights, as verified in Raman mapping and AFM topographies [9,28].…”

“…In order to further investigate spatial variations of the sheet resistance, we have measured large sequences of steps. The topographic analysis has shown that instead of a random distribution of step heights, a well-defined sequence of the step heights Force Microscopy (AFM) study and have been attributed to the growth process [28].…”

Traceably calibrated scanning Hall probe microscopy at room temperature

“…A measurement directly generates quantitative results albeit with reduced spatial resolution. It is applicable to a broader field range than magneto-optical indicator film techniques (Kabanov et al, 2005;McCord, 2015), which are limited by the saturation field of the sensor film. Unlike magneto-resistive sensors (Costa et al, 2015;Takezaki and Sueoka, 2008), Hall probes show excellent linearity without hysteresis and measure a well-defined field component perpendicular to the sensor plane.…”