Nanoscale ripple formation in Co/Si(100) thin films with Ar+ beam etching

Abstract

We have investigated the formation of nanoscale ripples on etched Co/Si(100) films with Ar+ beam in grazing incidence. Topography and dimensions of those nanoscale patterns were characterized by means of atomic force microscopy. Polycrystalline cobalt thin films were deposited by d.c. magnetron sputtering onto Si(100) wafers and, later transferred in situ to a process chamber for the production of ripples. Their average width, Wd, and separation between them, i.e. their periodicity Λ, were found to monotonously increase first with the etching time and, finally, reach saturation values for long irradation times (around 30 min). The same Ar+ beam etching applied on thicker Co films resulted in much wider and higher ripples, providing a more defined nanostructure for ulterior uniaxial magnetic anisotropy measurements. These changes in the ripple dimensions on increasing the Co film thickness are discussed in terms of the surface roughness in the as-deposited film.