Modeling of fluctuation processes on the biochemically sensorial surface of silicon nanowire field-effect transistors

Abstract

Affinity-type silicon-based nanowire biosensors rely on the biochemical interaction between target molecules and their molecular complements (recognition probes), located on the SiO2 insulator layer. This biochemical reaction is associated with twofold fluctuations through the mechanisms of binding/unbinding and regular charge thermal equilibrium processes. These fluctuations have a direct implication on the surface potential fluctuations which in turn affect, through the field effect transduction process, the electrical characteristics of the sensor device. The resulting noise could potentially contain detectable information, which can be extracted through the time constants (characteristic frequencies) related to the kinetics of the molecules under detection and their charge fluctuations. In this work, we present a comprehensive model for the fluctuations on the surface of the biosensor and attribute them to the two physical mechanisms. The spectral densities corresponding to these types of fluctuations add on the overall device noise spectrum and are directly detectable if they lie above the inherent noise level of the sensor device.

Modeling of Electrolyte Thermal Noise in Electrolyte-Oxide-Semiconductor Field-Effect Transistors

“…5. We note that the bulk electrolyte thermal noise dominates the output noise, and the noise contribution from the double-layer region is negligible, which is consistent with the conventional models where the double-layer noise resistance R D and its corresponding noise current source i nD are not treated in the small-signal equivalent circuit model with noise sources [6,7,11,15].…”

“…Zheng et al published a paper in 2009 demonstrating the increase of sensitivity by a factor of four by using the measurement of noise power spectral density (PSD) [9]. Very recently, Georgakopoulou et al have modeled the noise behavior from the binding/unbinding of target molecules with receivers as well as the thermal noise in the electrolyte, and showed an investigation on the screening effect to high-frequency noise [11]. In these previous studies, the noise coming from the double-layer region at the electrolyte-oxide interface has not yet been explicitly presented.…”

“…They have been used as ionsensitive FETs and pH-meters [1,2]. Many papers have been published on the modeling of noise in EOSFETs [5][6][7][8][9][10][11]. One notable modeling approach was presented by Hassibi et al in 2004 [5].…”

Field-effect sensors – from pH sensing to biosensing: sensitivity enhancement using streptavidin–biotin as a model system

“…22,23,112 Another example for conventional FET-sensors is that the surface layer could be modified with a biomoleculepermeable polymer layer which is proposed to operate by extending the effective distance over which charges are screened within the layer. 113 A final example of particular interest is the use of frequency-mode detection, 15,46,[114][115][116][117] where the current response is measured in the frequency domain instead of the time-domain (details can be found in ESI 6 †). The lack of wide-spread adoption of alternative operating methods may be due to: complexity, with the additional required steps required making them less commercially appealing; a lack of awareness in a rapidly changing field; or lack of reproducibility.…”

Modeling and Analysis of SiNW BioFET as molecular antenna for Bio-cyber interfaces towards the Internet of Bio-NanoThings

“…2. Equivalent circuit model for the transducer of the SiNW FET-based MC receiver [8] [11]. REF denotes the reference electrode.…”