Nanopatterning of mica surface under low energy ion beam sputtering

Irradiation of crystalline muscovite mica samples by 500 eV Ar+ ions at different incident angles can induce significant surface morphological variations. A periodic ripple pattern of nano-dimensions forms in the angle window 47 degrees-70 degrees. On the other hand, tilted conical protrusions develop on the surface at grazing incidence angles around 80 degrees. From the derivative of the topographic images the distribution of the side-facet slopes in the ion incidence plane are measured, which is found to be strongly related to the pattern morphology. Additionally, it has been shown that, for the ripple structures, the base angles can be tuned by changing the ion fluence. An asymmetric sawtooth profile of the ripples obtained at low fluence is transformed to a symmetrical triangular profile at high fluence. As the slopes are found to be small, the pattern formation is not provoked by the gradient-dependent erosion mechanism rather it is the general effect of the curvature-dependent sputtering phenomena. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3699045]