Van der Waals surface of InSe as a nanorelief standard in metrology of nano-objects

Rapid progress of nanotechnology requires metrological provision systems and, first of all, a standard of length in the nanometer range including a surface nanorelief standard. One such standard is the periodical arrangement of atoms in the lattice of single crystals. The cleavage surface of layered crystals is very suitable in this respect. The cleavage surface of an InSe layered semiconductor is a van der Waals surface. It features a high chemical stability and a low roughness, is easy to obtain by cleavage, and has extended atomically smooth areas of a highly ordered rhombohedral lattice with unit cell parameter $a$ = 0.4003 nm. Therefore, this surface, like the surface of highly oriented pyrographite, can be used as a nanorelief standard.