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
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