Abstract <p>The formation of self-ordered nanostructures on the surface of single-crystal silicon and germanium using cluster ion treatment is considered. Low-energy argon cluster ions are used for more efficient nanostructuring of the target surface. Using an atomic force microscope, the morphology of the target surface is analyzed before and after treatment with an argon cluster ion beam. It is shown that the treatment with low-energy argon cluster ions at an incidence angle of 60° relative to the surface normal leads to effective nanostructuring of the silicon and germanium surface at an etching depth commensurate with the amplitude of the nanostructures. The roughness parameters (root mean square roughness and total roughness) of the original and processed target surfaces are given. The period and amplitude of the nanostructures formed on the surfaces of silicon and germanium are compared. It has been determined that for an ion fluence of 1 × 10¹⁵ cm^–2, the period of nanostructures on the surfaces of single-crystal silicon and germanium is about 200 nm; in the case of germanium, the period is larger. The amplitude of nanostructures on the surface of silicon and germanium is about 65 and 50 nm, respectively. After treatment with argon cluster ions, a more developed surface of monocrystalline silicon is formed compared to germanium.</p>