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 FexSi 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 process for the pattern formation on Si in the case of Fe, Mo, Ni, W, and Pt co-deposition.
Highlights
The simultaneous co-deposition of small amounts of atoms during ion beam erosion of surfaces has a tremendous influence on the self-organized nano pattern formation [1,2,3,4,5,6].Several groups have recently demonstrated that in particular co-deposition of Fe and Mo surfactant atoms at room temperature induce pronounced dot and ripple patterns on Si substrates, even during normal and near normal ion incidence sputter erosion [2,3,4, 6,7,8]
We introduced a pattern formation scenario based on initial chemical effects and phase separation processes
We investigate pattern formation on Si substrates for normal incidence 5 keV Xe ion irradiation at room temperature under simultaneous oblique angle co-deposition of Fe, Ni, Cu, Mo, W, Pt, or Au surfactant atoms using the same experimental setup used for our previous work [2] on Fe co-deposition onto Si
Summary
Several groups have recently demonstrated that in particular co-deposition of Fe and Mo surfactant atoms at room temperature induce pronounced dot and ripple patterns on Si substrates, even during normal and near normal ion incidence sputter erosion [2,3,4, 6,7,8]. We provide new experimental studies using the same experimental setup, but carried out with a number of different co-deposited metal atoms. In this way, we are able to generalize the validity of our pattern formation scenario and provide evidence that in particular the co-deposition of metals prone to disilicide formation results in pronounced dot and ripple patterns on Si substrates
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