Sammendrag
The formation of GaSb nanopillars by low energy ion sputtering have been observed in real time by in-situ spectroscopic ellipsometry. By modelling the optical properties of the nanostructures as a graded anisotropic effective medium layer, the height of the nanopillars was derived for every 5th second during the formation. The method was verified by ex-situ AFM on a set of samples with identical formation conditions and increasing ion exposure time, with average pillar heights ranging from 20 to 80 nm. Three different formation regimes were observed, an initial removal of oxide and surface smoothing regime, a rapid pillar formation regime, and finally a slow formation regime. Saturation was not observed. By in-situ ellipsometry the dependence of these regimes on sputtering conditions (ion energy, ion flux and temperature) was studied. The different regimes were found to be governed by different sputtering parameters. These observations give new insight into the formation mechanisms of GaSb nanopillars, which may allow for increased control of the morphology of the structures, and may also ease the search for other materials which will form nanopillars during ion sputtering.
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