Fabrication of amorphous pillar silicon structures showing visible photoluminescence (PL) by naked eye is reported. Some attempts involving silicon etching processes were previously performed by other authors, but PL from the resulting pillar structures was never observed.
The pillar silicon structures were grown by Plasma Enhanced Chemical Vapour Deposition (PECVD) of hydrogenated amorphous silicon (a-Si:H) over the surface of porous aluminum oxide films, previously formed by anodization process. Alumina pore dimensions varied between 4-200 nm, depending on the parameters of the anodization process. The size of the grown a-Si:H pillars was quite homogeneous and could be tightly controlled by the anodization conditions. Immediately after PECVD process, PL from the pillar structure was very weak and not visible by naked eye, but after a short electrochemical treatment in 1% wt HF at 2 mA/cm2 it became quite bright and visible at normal daylight. A red shift, very similar to the one shown by porous silicon formed on monocrystalline substrates, was observed during samples drying after the electrochemical treatment.