Ion-induced roughening and ripple formation on polycrystalline metallic films

Abstract

We present a study of nanopattern formation on polycrystalline Ni surfaces upon low energy Ar ion bombardment. At low angles of ion incidence an isotropic, rough morphology develops on the surface while at grazing incidence a ripple structure parallel to the ion beam direction is formed (so-called perpendicular mode ripples). To explain this behavior we propose a model which is based on a combination of (a) surface roughening due to sputter yield variation between different crystalline grains and (b) anisotropic nonlinearity resulting from the oblique angle bombardment. By computer simulations we show that the combination of these two phenomena excellently reproduces the experimental behavior, in particular the dependence of the surface morphology on the ion incidence angle. Importantly, the formation of ripples at grazing incidence does not involve any linear instability, in strong contrast to the present model of the ripple formation process.

Orientation‐dependent nanostructuring of titanium surfaces by low‐energy ion beam erosion

“…Generally, there is a power-law scaling behavior between ripple period and erosion time, while erosion time can be expressed by the removal depth too 6. As shown in the CM measurements, there are different removal depths with respect to the local crystal alignment.Škereň et al23 obtained similar results on crys-tal orientation dependent ion etching for argon ion erosion(5 keV) of thin, polycrystalline nickel films. In particular, the study suggests a correlation of the orientation-dependent etching rate to the angular dependence of the sputtering yield.…”

“…However, despite ripples were also observed at normal ion incidence, an incidence angle of was necessary, in which a crystal orientation dependent formation was obtained. Argon ion irradiation experiments at nickel films reveal even higher incidence angles of 70° or 80° to be necessary for ripple formation 23 . However, the nickel grain sizes are very tiny, and the ripples formed at high incidence angles comprise a large amount of grains, which indicates that those formation conditions are not correlated to any crystal alignment effect but the distinct experimental process geometry at grazing ion incidence.…”

“…Argon ion irradiation experiments at nickel films reveal even higher incidence angles of 70 • or 80 • to be necessary for ripple formation. 23 However, the nickel grain sizes are very tiny, and the ripples formed at high incidence angles comprise a large amount of grains, which indicates that those formation conditions are not correlated to any crystal alignment effect but the distinct experimental process geometry at grazing ion incidence. In contrast, in the present study already at normal ion incidence, the local crystal structure determines the nanostructure formation.…”

Tailoring the magnetic anisotropy, magnetization reversal, and anisotropic magnetoresistance of Ni films by ion sputtering

“…Crystalline Ni (001) films were deposited on MgO (001) substrates by molecular beam epitaxy at a base pressure of 2 × 10 −10 mbar [22]. The substrate was annealed at 600…”

Nanopatterning graphite by ion-beam-sputtering: Effects of polycrystallinity

“…This observation leads them to the conclusion that the polycrystallinity did not influence the pattern evo-lution. On the other hand, Škereň et al 14 reported that the variation of the sputter yield depending on the orientation of the grains induced the surface instability during IBS, and well reproduced the morphological evolution of polycrystalline Ni films without invoking the instability owing to the curvature dependent erosion 3 . The two conclusions on the effects of the polycrystallinity contradict to each other.…”