(a) Schematic of nanoimprint lithography process: (1) imprinting using a mold to create a thickness contrast in a resist, (2) mold removal, and (3) pattern transfer using anisotropic etching to remove residue resist in the compressed areas. (b) SEM micrograph of a perspective view of strips formed into a PMMA film by imprint. The strips are 70 nm wide and 200 nm tall, having a high aspect ratio, a surface roughness less than 3 nm, and nearly perfect 90° corners. (c) SEM micrograph of the mold that was used to imprint the PMMA strips shown in (b). Reproduced from [4] with permission of American Vacuum Society.