Epitaxial graphene on SiC: modification of structural and electron transport properties by substrate pretreatment

Abstract

The electrical transport properties of epitaxial graphene layers are correlated with the SiC surface morphology. In this study we show by atomic force microscopy and Raman measurements that the surface morphology and the structure of the epitaxial graphene layers change significantly when different pretreatment procedures are applied to nearly on-axis 6H-SiC(0 0 0 1) substrates. It turns out that the often used hydrogen etching of the substrate is responsible for undesirable high macro-steps evolving during graphene growth. A more advantageous type of sub-nanometer stepped graphene layers is obtained with a new method: a high-temperature conditioning of the SiC surface in argon atmosphere. The results can be explained by the observed graphene buffer layer domains after the conditioning process which suppress giant step bunching and graphene step flow growth. The superior electronic quality is demonstrated by a less extrinsic resistance anisotropy obtained in nano-probe transport experiments and by the excellent quantization of the Hall resistance in low-temperature magneto-transport measurements. The quantum Hall resistance agrees with the nominal value (half of the von Klitzing constant) within a standard deviation of 4.5 × 10(-9) which qualifies this method for the fabrication of electrical quantum standards.

Comeback of epitaxial graphene for electronics: large-area growth of bilayer-free graphene on SiC

“…Thus the sample can be considered as bilayer-free. This is a result of the uniform graphene formation by the PASG and the conservation of low step heights since high step edges are known to favor bilayer formation [4,12,19]. Only at substrate defects such as micropipes and in some cases very close to the sample edge bilayer patches were observed (figure S1(b), supplementary information).…”

“…Irregular step heights are usually connected to graphene bilayer formation with a surface coverage of a few percent. Those metallic bilayer patches can short-circuit closely spaced contacts and can severely deteriorate the electronic properties [17][18][19]. These drawbacks so far have delayed the implementation of SiC sublimation growth for wafer-scale device fabrication.…”

Nonequilibrium mesoscopic conductance fluctuations as the origin of 1/f noise in epitaxial graphene

“…1(a). The graphene film had been grown in argon at atmospheric pressure within 5 min at a temperature of 1750 • C [31]. Raman spectroscopy was used on samples with similar growth conditions to the one presented here to confirm the presence of monolayer graphene, with only very few electrically separated bilayer patches [ Fig.…”

Crystallization of Thin Copper Films on Silica Substrate for Graphene Growth

“…The phase shift of the resonant oscillations of the cantilever is fixed when the conditions for the elastic interaction of the probe with the sample surface are changed. Measurements in the phase contrast mode reveal changes in the microhardness (microelasticity) of investigating material, which makes it possible to detect the carbon film on surface and to distinguish the area of graphene with different number of layers …”

“…Measurements in the phase contrast mode reveal changes in the microhardness (microelasticity) of investigating material, which makes it possible to detect the carbon film on surface and to distinguish the area of graphene with different number of layers. [10][11][12][13] At the same time, the interpretation of the phase contrast image is complicated due to the impact of elastic repulsion, contact and non-contact adhesion on the cantilever. [14] To reduce the specific contribution of adhesion forces to the dissipation of the energy of the oscillating cantilever tip, that is, to the resulting picture of the phase image, we chose contactless silicon probes with greater rigidity (cantilever force constant 12-20 N m À1 ), and therefore with greater initial probe energy.…”