Biomolecule detection using a silicon nanoribbon: accumulation mode versus inversionmode

Abstract

Silicon nanoribbons were fabricated using standard optical lithography from silicon oninsulator material with top silicon layer thicknesses of 100, 60 and 45 nm. Electrically thesework as Schottky-barrier field-effect transistors and, depending on the substrate voltage,electron or hole injection is possible. The current through the nanoribbon is extremelysensitive to charge changes at the oxidized top surface and can be used for biomoleculedetection in a liquid. We show that for detection of streptavidin molecules theresponse is larger in the accumulation mode than in the inversion mode, althoughnot leading to higher detection sensitivity due to increased noise. The effect isattributed to the location in depth of the conducting channel, which for holes is closerto the screened surface charges of the biomolecules. Furthermore, the responseincreases for decreasing silicon thickness in both the accumulation mode and theinversion mode. The results are verified qualitatively and quantitatively through atwo-dimensional simulation model on a cross section along the nanoribbon device.