Selective dissolution of silicon in porous amorphous Si_1-xC _x:H

We have investigated the properties of porous layers obtained by anodisation of hydrogenated amorphous silicon-carbon alloys (a-Si _1-xC_x:H) in HF electrolyte. Room-temperature photoluminescence of bulk and porous a-Si_1-xC_x:H samples for different carbon concentrations reveals that, at the same carbon content, the photoluminescence energy is much higher for porous a-Si_1-xC _x:H than for the bulk material. Infrared characterisation of the porous layers suggests that carbon concentration is higher in porous a-Si _1-xC_x:H than in the starting material, accounting for the luminescence blue shift. This carbon enrichment, due to selective Si dissolution during porous layer formation, has been confirmed and quantified by secondary ion mass spectroscopy.