Fig. 3: Scanning images of microscale gratings and graphene.

a, b Two-dimensional (a) and line (b) scan images of a 2 μm-period grating with a vertical orientation. The intensity profile shown in b is extracted along the solid line in a. The insert in a shows a microscopic image of the grating, while the insert in b gives the fast Fourier transform of the line-scan intensity. c, d Two-dimensional (c) and line (d) scan images of a 2 μm-period grating with a horizontal orientation. The intensity profile shown in d is extracted along the solid line in c. The insert in c shows a microscopic image of the grating, while the insert in d gives the fast Fourier transform of the line-scan intensity. e–h Microscopic images (e, f) and scanning transmission images (g, h) of a graphene sample on a CaF₂ substrate. The images in f, h are magnified images of the small graphene sample marked in e, g, respectively