Fabrication of n-type porous silicon membranes for sensing applications

In this work we have proposed a PSi based flow through bio-sensor able to perform fast and sensitive real time analysis. The present work is summarized as: 1. We have presented a simple fabrication method for n-type PSi free-standing membranes with straight and smooth pores of up to ~100nm of diameter. 2. A two solution method is presented to fabricate free standing porous membranes. 3. Our process maintains a very good planarity of the interface as demonstrated by the fabrication of very thin and large area free standing membranes. No HF concentration gradient effect is noticed. 4. We found that membranes detachment does not require a high current burst but it is a self-limited process that involves a thin transitional layer at the bottom of the porous region. 5. Covalent functionalization of silicon surface is found to be suitable used to stabilize the porous surface and to act as intermediate layer for binding of other bio-molecules. 6. Role of non-specific binding in sensing efficiency is analyzed by comparing flow over and flow-through sensing for sensor fabricated on silicon substrate and sensor in freestanding nature. 7. Real time sensitivity per unit length of 0.0053degree/NaCl% and 0.0148degree/NaCl% was observed respectively for porous alumina and PSi membranes and PSi was found more suitable and sensitive for bio-sensing applications.