Stoichiometric influences on ion beam nanopatterning of CoSi binary compound

摘要

Impact of initial stoichiometry of binary compound on surface nanostructure formation with low energy ion irradiation has been studied. Different stoichiometric CoSi surfaces are irradiated by Ar+ ion beam with energy of 700 eV, fluence of 7.5x10(18) ions cm(-2) and angle of incidence 67 degrees. Within a narrow window of stoichiometric variation, self-organized nanoripples have been observed. The ripple structures are well formed for stoichiometric ratios of 40:60 for Co:Si. Nanoscale ripples start growing for a concentration of about Co22Si78. The root mean square (rms) roughness initially decreases and then increases slightly as Co increases from low to medium concentrations. The evolution of different morphologies has been corroborated from the behavior of power spectral densities (PSD). Correlation lengths are extracted from atomic force microscopy (AFM) images to corroborate the ripple formation region only within a specific stoichiometric range. Differential sputtering yields provide a rationale for the observed pattern evolution.