Stabilization of hydroxyl-terminated silanes in porous silicon for in-situ DNA synthesis

Passivation of porous silicon sensors is a critical issue for achieving high sensitivity and selectivity toward biomolecule targets that may be detected in complex physiologic solution. Without appropriate passivation, degradation of the porous silicon matrix inhibits the repeatability of optical measurements and limits applications in complex media. In this work, we present a method for stabilizing TEOS-HBA monolayers in porous silicon. Annealing of the silane at 200°C for 16 hours, followed by a deionized water wash for a minimum of one hour, results in a porous silicon surface that is highly stable in a number of solvents. Annealing improves cross-linking of surface-attached silane molecules for added stability, and hydrolyzing facilitates removal of weakly bound multilayers. This surface treatment procedure is of considerable interest in applications such as DNA synthesis where hydroxyl functionality is critical and a thick silane surface coating is not desired.