Figure 3: Orientation of stripes on graphene and hBN. | Nature Communications

Figure 3: Orientation of stripes on graphene and hBN.

From: Switchable friction enabled by nanoscale self-assembly on graphene

Figure 3

(a) Tapping mode topography image of graphene islands grown by van der Waals epitaxy on exfoliated hBN. The image has been differentiated along the horizontal axis for clarity. Graphene islands can be distinguished from the hBN surface by the presence of a moiré pattern, which is partially outlined in black for one of the grains. The sample surface is covered with stripes of period 4.3±0.1 nm, oriented along one of three distinct axes rotationally separated by 60°. The stripe period is the same on graphene and hBN, and the stripes frequently appear to cross the graphene/hBN boundary without a phase slip. Scale bar, 50 nm. (b) Fast Fourier transform (FFT) of the topography signal used to produce a. The moiré pattern within the graphene grains appears as a sixfold-symmetric pattern with segments extending 70 μm−1 from the origin; these protruding segments are parallel to the momentum-space moiré lattice vectors. The dominant stripe domain on graphene and hBN produces a pair of isolated points in the FFT, one of which is circled in black. The stripe axis is rotated 26±4° from the moiré lattice vectors, indicating that the stripe axes are nearly aligned with the armchair axes of the graphene and hBN. The quoted angular precision reflects the width of the moiré peaks; we also expect a few-degree systematic error in the angular estimate, as a misalignment between graphene and hBN lattices of 0.1°—a reasonable expectation for van der Waals epitaxial heterostructures23—would rotate the moiré pattern by 4° with respect to the graphene lattice. The small area of nearly vertical stripes in a produces a pair of points, circled in red, which can barely be seen with this colourscale. Scale bar, 100 μm−1.

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