Drain current control in a hybrid molecular/MOSFET device

We have developed a hybrid molecular/MOSFET, which is sensitive to the presence of a molecular layer attached to its surface. The application of the molecular layer was investigated by observing changes in the threshold current of the device. A significant shift in the threshold voltage was attributed to an increase in the electron charge density in the MOSFET channel, resulting from an increase in the positive fixed charge at the native oxide surface. A numerical simulation supports this conclusion. It is speculated that the molecules protonate the surface of the SiO2 due to the higher acidity of the molecular groups compared to that of the native oxide. To assess the validity of this hypothesis a series of molecules with similar structure but with different acidities (pKa values) were investigated. Preliminary results showing the systematic variation of ΔVth and pKa are presented.