Transient-enhanced Si diffusion on natural-oxide-covered Si(001) nano-structures during vacuum annealing

Abstract

The morphology of annealed patterned Si(0 0 1) wire templates was studied by several techniques. We found an enormous Si-mass transport on the Si surface at usual oxide desorption temperatures around 900°C under UHV conditions. Heat treatment of 5min transforms the initially rectangular wire profiles with a height of 300nm to flat (<100nm) and faceted triangular ridges exhibiting thermodynamically preferred {111}- and {311}-facets. It was found that the natural SiO2 on the predefined wire pattern must be responsible for the degradation of the wire structure. Removing the SiO2 layer from the Si wires ex situ with an HF dip preserves the rectangular structures during high-temperature annealing. The Si–SiO2 interface was investigated with high-resolution transmission electron microscopy to image the Si wire surface and the natural oxide layer in detail.