Laser-Assisted Formation of Porous Silicon in Diverse Fluoride Solutions:  Hexafluorosilicate Deposition

Photoluminescent porous silicon has been produced in a variety of etchants using laser-assisted etching of silicon without an applied potential. Porous silicon (por-Si) produced from etchants containing K +, Cs +, or Rb + can have cubic crystallites of hexafluorosilicate on top of and embedded in the porous silicon film. These are formed during etching from the metal ion and the etch product, Si, via heterogeneous nucleation and growth. The photoluminescence of the hexafluorosilicate-coated por-Si on excitation with UV light is blue-shifted (590−610 nm), as compared to porous silicon that shows red photoluminescence (∼640 nm), even though the pure hexafluorosilicates exhibit no photoluminescence of their own.