Interest in biosensors based on field-effect transistors (FETs), where an electrically operated gate controls the flow of charge through a semiconducting channel, is driven by the prospect of integrating biodetection capabilities into existing semiconductor technology. In a number of proposed FET biosensors, surface interactions with biomolecules in solution affect the operation of the gate or the channel. However, these devices often have limited sensitivity. We show here that a FET biosensor with a vertical gap is sensitive to the specific binding of streptavidin to biotin. The binding of the streptavidin changes the dielectric constant (and capacitance) of the gate, resulting in a large shift in the threshold voltage for operating the FET. The vertical gap is fabricated using simple thin-film deposition and wet-etching techniques. This may be an advantage over planar nanogap FETs, which require lithographic processing. We believe that the dielectric-modulated FET (DMFET) provides a useful approach towards biomolecular detection that could be extended to a number of other systems.

A photolithography-based method capable of size reduction to produce sub-10-nm Si nanowire arrays on a wafer scale is described. By conformally depositing a material (silicon oxide or silicon) that has a different etching property over a lithographically defined sacrificial sidewall and selectively removing the sacrificial material, the sidewall material is preserved and can serve as nanopattern mask for further processing. The resolution of this method is not limited by photolithography but by the thickness of the material deposited. The application of size reduction nano-patterning method can range from the fabrication of biosensors to model catalyst systems.

No abstract

No abstract