Spatial distribution of Ar on the Ar-ion-induced rippled surface of Si

We have measured spatial distribution of Ar atoms on the rippled surface generated on Si undergoing 60 keV Ar bombardment at a 60° angle of ion incidence. Elemental mapping and line scans using energy dispersive x-ray spectrometry attached in a scanning electron microscope confirmed that subsequent to the interpeak shadowing of incident ion flux, most of the argon atoms are incorporated around the middle part of the front slope of ripple facing the ion beam as compared to the rear slope. The spatial extension of the argon rich phase amounts about half of the ripple wavelength. The experimentally observed compositional heterogeneity between the two faces of the ripples agrees reasonably good to the well-known Monte Carlo ion simulator TRIM based theoretical calculations.

Figure 1

Schematic diagram showing the structure and morphology of a ripple feature obtained from TEM measurements (see Ref. 9 for details).

Figure 2

Representative AFM images of the Ar bombarded Si surfaces with a fixed ion flux of $18\mu \mathrm{A}{\mathrm{cm}}^{-2}$ for ion fluence $3.7\times {10}^{17}\text{ions}{\mathrm{cm}}^{-2}$ (a) and $1\times {10}^{18}\text{ions}{\mathrm{cm}}^{-2}$ (b). The height profiles shown with each of the images are taken along the solid line drawn over the images. Arrow mark shows the direction of the projection of ion flux on to the surface. The portion of the height profile of (b) selected by the dotted box is also shown along with the calculated slope angle variation (open circles) over the height profile. The lower half shows the amplitude, wavelength and their ratio for three different fluences.

Figure 3

(Color online) Showing SEM image (a), x-ray map of Ar (b) and Si (c) over the Si surface ripples for the Ar fluence of $3.7\times {10}^{17}\text{ions}{\mathrm{cm}}^{-2}$.

Figure 4

(Color online) Showing SEM image (a) along with the SEM image intensity profile, Ar and Si intensity profile obtained from EDS line scan taken along the line shown on the SEM image for the Ar fluence of $1\times {10}^{18}\text{ions}{\mathrm{cm}}^{-2}$. Arrow mark on the SEM image indicates the direction of the projection of ion flux on to the surface. Also shown are the x-ray maps of Ar (b) and Si (c).

Figure 5

(Color online) Showing SEM image (a) along with the SEM image intensity profile, Ar and Si intensity profile obtained from EDS line scan taken along the line shown on the SEM image for the Ar fluence of $1.5\times {10}^{18}\text{ions}{\mathrm{cm}}^{-2}$. Arrow mark on the SEM image indicates the direction of the projection of ion flux on to the surface. Also shown are the x-ray maps of Ar (b) and Si (c).

Figure 6

Plots showing the variation of areal density and penetration depth of Ar as a function of angle of incidence as calculated from TRIM simulation for 60 keV Ar bombardment on Si.