Gallium indium eutectic masking prior to porous silicon formation creates unique spatially-dependent chemistries

We demonstrate that gallium indium (GaIn) eutectic can be used to create interesting crystalline Si/porous silicon (cSi/pSi) platforms that exhibit unique analyte- and spatially-dependent photoluminescence (PL) responses. Here we characterize these cSi/pSi regions by using profilometry, scanning electron microscopy (SEM), wide-field PL microscopy, and Fourier transform infrared (FTIR) microscopy. As we move along a vector from the cSi/pSi interface out into "bulk" pSi, the: (i) analyte-dependent, PL-based response initially increases and then decreases; (ii) total PL emission intensity, in the absence of analyte, increases; (iii) pSi thickness increases; and (iv) relative O₂Si-H to Si-H band amplitude ratio decreases. Thus, the analyte-dependent PL response magnitude is correlated to the extent of pSi oxidation; which can be easily controlled by using GaIn eutectic as a mask during the pSi fabrication process.