ON THE CORRELATION OF AQUEOUS AND NONAQUEOUS IN-SITU AND EX-SITU PHOTOLUMINESCENT EMISSIONS FROM POROUS SILICON - EVIDENCE FOR SURFACE-BOUND EMITTERS

Porous silicon samples were prepared by anodizing p-doped Si(100) subs trates in both aqueous (HF/H2O, HF/CH3OH, HF/CH3OH/H2O, HF/C3H5OH/H2O) and nonaqueous (MeCN/HF) media. The time-dependent porous silicon pho toluminescence (PL) was monitored during the etch (in situ) and after removal from the etch solution (ex situ). Correlation of the ex situ a nd in situ PL indicates that the composition of the etchant solution p lays an extremely important role in the onset, time-dependent intensit y, and Lifetime of the emission, both in and out of solution. The effe ct of etchant solution additives (ethylene glycol, CH3OH, C2H5OH, NaF, HCl, and NaCl) on the porous silicon PL both during and following the etching cycle, was also determined. The distinct and different correl ations found between aqueous and nonaqueous etchants provide insights into the mechanism of FL. These results, when considered in the contex t of quantum chemical modeling, strongly suggest surface-bound silicon oxyhydride moieties as the source of the porous silicon PL.