Room temperature metal–insulator–semiconductor (MIS) hydrogen sensors based on chemically surface modified porous silicon

Porous silicon (PS) surface obtained by electrochemical anodization of p-silicon was modified using chlorides of palladium (Pd), ruthenium (Ru) and platinum (Pt) by electroless chemical method for passivating the surface states to a large extent and to stabilize the material. PS surface was characterized using grazing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM) and energy dispersive X-ray analysis (EDAX). Pd–Ag (26%) was used as the rectifying contact to PS in the Pd–Ag/PS/Si/Al MIS (metal–insulator–semiconductor) structure. Aluminium (Al) electrode was evaporated on the backside of silicon (Si) for ohmic contact formation. For hydrogen sensor applications transient response, repeatability and stability of the MIS structure were studied at room temperature for Pd, Ru and Pt modified surfaces. It was observed that the Pd modified samples showed optimum response with faster response time and recovery time (8 s and 207 s respectively) in comparison with Ru and Pt modified samples. The stability experiments showed minimum fluctuations and consistent performance of Pd modified PS sensors.