Stoichiometric influences on ion beam nanopatterning of CoSi binary compound

Abstract

Impact of initial stoichiometry of binary compound on surface nanostructure formation with lowenergy ion irradiation has been studied. Different stoichiometric CoSi surfaces are irradiated by Ar+ion beam with energy of 700 eV, fluence of 7.5×1018ions cm−2and angle of incidence 67◦. Withina narrow window of stoichiometric variation, self-organized nanoripples have been observed. Theripple structures are well formed for stoichiometric ratios of 40:60 for Co:Si. Nanoscale ripples startgrowing for a concentration of about Co22Si78. The root mean square (rms) roughness initiallydecreases and then increases slightly as Co increases from low to medium concentrations. Theevolution of different morphologies has been corroborated from the behavior of power spectraldensities (PSD). Correlation lengths are extracted from atomic force microscopy (AFM) imagesto corroborate the ripple formation region only within a specific stoichiometric range. Differentialsputtering yields provide a rationale for the observed pattern evolution.