Temperature influence on the production of nanodot patterns by ion beam sputtering of Si(001)

The temperature influence (T=300-625 K) on the production of nanodot patterns by 1 keV Ar+ ion beam sputtering (IBS) of Si(001) is addressed. The surface morphology was studied by atomic force microscopy, transmission electron microscopy, and grazing x-ray scattering techniques. Three different T regimes are observed: (i) First, the pattern does not change significantly up to 425 K, with the nanodot volume being mostly crystalline. (ii) Second, in the 425-525 K range, the pattern is still present but the nanodot height decreases with T and the crystalline core contribution to the dot morphology progressively diminishes. This trend is accompanied by a continuous decrease of the average interdot distance and an emerging strain in the crystalline lattice of the nanostructures. Above 500 K, the pattern is mainly dominated by the amorphous surface layer. (iii) Finally, the pattern formation is precluded above 550 K, yielding a flat and featureless surface. These results not only have technological implications regarding the control over the pattern characteristics, but also provide relevant information to contrast the existing theories of pattern formation by IBS.