Formation of straight 10 nm diameter silicon nanopores in gold decorated silicon.

We observe pore formation with diameters in the 10 nm range in silicon when it is covered with gold particles. This pore etching occurs when the sample is put in 5 wt % hydrofluoric acid (HF) solution for a few minutes. The pores form along the 100 direction, which is also the preferred direction of macro- and mesopores electrochemically etched into silicon. No etching occurs if the dissolved oxygen is removed from the aqueous HF solution or the gold is removed from the silicon surface. This leads to the assumption that the dissolved oxygen acts as an oxidant as in the case of stain etching with gold as cathodic material. A tentative model is suggested to explain why all of the observed nanopores have roughly the same diameter of about 10 nm. These pores can occur for inhomogeneously gold-covered planar silicon surfaces but also in MBE (molecular beam epitaxy) grown silicon nanowires since these nanowires are covered unintentionally with gold nanoclusters at their cylindrical surface.