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Single Trap Phenomena for Biosensing

Single trap phenomena in the dielectric of liquid-gated nanowire FETs are used as a basic principle for a novel highly sensitive approach to monitor the gate surface potential. An increase in Si NW FET sensitivity of 400% was demonstrated.

Sensitivity Enhancement of Si Nanowire FET Biosensors Using Single Trap Phenomena

Jing Li, Sergii Pud, Mykhaylo Petrychuk, Andreas Offenhäusser, Svetlana Vitusevich

Mechanism of sensitizing the nanowire pH measurements by the single trap phenomenon.Mechanism of sensitizing the nanowire pH measurements by the single trap phenomenon.

Abstract: Trapping-detrapping processes in nanostructures are generally considered to be destabilizing factors. However, we discovered a positive role for a single trap in the registration and transformation of useful signal. We show that fluctuation phenomena related to the single-trap modulation of the drain current can be used as a versatile approach for tracking surface potential changes with increased sensitivity. Liquid-gated Si NW FETs were fabricated with dimensions small enough for a single trap to have a considerable impact on electric transport in the conducting channel. It is shown that the kinetics of the registered two-level switching of drain current in liquid-gated Si NW FETs demonstrates a deviation from behavior according to the Shockley-Reed-Hall theory with considerably stronger capture time dependence on drain current. The mechanism of the effect is related to the change in charge state of a single trap and is explained in the framework of the Coulomb blockade concept. The observed phenomenon is used to realize a new detection approach, which is at least 400% more sensitive to surface potential than conventional methods based on the change in value of the drain current. The efficiency of suggested biosensing method can be further improved by a special design of NW FET structures.

Nano Lett., 2014, 14 (6), pp 3504–3509 DOI: 10.1021/nl5010724