Scattering images of lamellar-type silicon nanostructures at incident angles of (a) 0.10°, (b) 0.16° and (c) 0.50°. The direct beam position and the surface horizon position are denoted by dotted and solid lines, respectively. (d) A SEM image of the silicon nanostructure. The inset shows the cross-sectional SEM image. (e) Scattering profiles for the first-order BRs, obtained from the boxed regions in (a)–(c).