The role of phase separation for self-organized surface pattern formation by ion beam erosion and metal atom co-deposition

Abstract

We investigate the ripple pattern formation on Si surfaces at room temperature during normal incidence ion beam erosion under simultaneous deposition of different metallic co-deposited surfactant atoms. The co-deposition of small amounts of metallic atoms, in particular Fe and Mo, is known to have a tremendous impact on the evolution of nanoscale surface patterns on Si. In previous work on ion erosion of Si during co-deposition of Fe atoms, we proposed that chemical interactions between Fe and Si atoms of the steady-state mixed Fe x Si surface layer formed during ion beam erosion is a dominant driving force for self-organized pattern formation. In particular, we provided experimental evidence for the formation of amorphous iron disilicide. To confirm and generalize such chemical effects on the pattern formation, in particular the tendency for phase separation, we have now irradiated Si surfaces with normal incidence 5 keV Xe ions under simultaneous gracing incidence co-deposition of Fe, Ni, Cu, Mo, W, Pt, and Au surfactant atoms. The selected metals in the two groups (Fe, Ni, Cu) and (W, Pt, Au) are very similar regarding their collision cascade behavior, but strongly differ regarding their tendency to silicide formation. We find pronounced ripple pattern formation only for those co deposited metals (Fe, Mo, Ni, W, and Pt), which are prone to the formation of mono and disilicides. In contrast, for Cu and Au co-deposition the surface remains very flat, even after irradiation at high ion fluence. Because of the very different behavior of Cu compared to Fe, Ni and Au compared to W, Pt, phase separation toward amorphous metal silicide phases is seen as the relevant pro-

Self-organized nanopatterning of silicon surfaces by ion beam sputtering

“…Also, Ag-Pd and Pb-Ir are close in nuclear charge, which allows to distinguish between collisional and chemical effects. In agreement with [122], only the co-deposition of metals prone to silicide formation did lead to surface nanopatterning. However, the authors of [123] argue that the ability of the co-deposited metal to form silicide appears to be a necessary, but not a sufficient condition for nanopatterning.…”

“…The relevance of silicide formation and the emergence of sputtering rate differences on the target surface were recently confirmed by Hofsä ss et al [122]. In this study, the authors again used the same experimental set-up depicted in Fig.…”

“…In fact, clear ripple patterns were only observed for co-deposited metals (Fe, Mo, Ni, W, and Pt) which are prone to the formation of mono and disilicides. Some of the morphologies obtained in [122] are shown in Fig. 32.…”

Sharp transition from ripple patterns to a flat surface for ion beam erosion of Si with simultaneous co-deposition of iron

“…19 The surface topography of the sputter eroded samples were analyzed by atomic force microscopy (AFM) in contact mode using a Nanosurf microscope and Si cantilevers from NanoAndMore GmBH with mean tip radius 7 nm. AFM measurements were done using the Nanosurf Easyscan software.…”

Nanostructures on fused silica surfaces produced by ion beam sputtering with Al co-deposition

“…Ion beam parameters (species, incidence angle, energy, flux, etc) and substrate parameters (material, temperature, initial surface topography, etc) interact to generate the features of such nanopatterns. Recently, numerous experiments on sputtering with simultaneous co-deposition [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] and theoretical studies [40][41][42][43][44][45][46][47] on simultaneous metal co-deposition during IBS or surfactant sputtering [32-38, 46, 47] have been performed to elucidate the formation mechanism of self-organized nanostructures and to generate various nanopatterns. In principle, the simultaneous use of metal atoms modulates the sputtering yield of the substrate during IBS, which results in diverse physical and chemical phenomena (e.g., island formation or phase separation).…”