Transformation, green to orange-red, of a porous silicon photoluminescent surface in solution

The green and orange-red photoluminescent (PL) emissions characteristic of a porous silicon (PS) surface are excited with a variety of UV light sources and observed during and directly following the in situ (in solution) etching of a PS surface in a 20% HF in MeOH or 20% HF in H2O solution. Experimental observations of the time dependent behavior of this in situ PL are combined with a quantum chemical modeling of the low-lying electronic states of the silanone-based silicon oxyhydrides to suggest that the initially observed and relatively long-lived green FL, its subsequent transformation to a final orange-red emission, and its stabilization in an ethylene glycol solution are to be associated with oxyhydride electronic transitions and the chemical transformation of surface-bound oxyhydrides.