The potential use of silicon nanowires as parts of future devices has triggered an increased interest in silicon nanowire research. The usage of COMSOL Multiphysics can improve the sensitivity of Bioelectronics to extend their stability and utility. Biosensors based on silicon nanowires promise highly sensitive dynamic label-free electrical for detection of biomolecules organic. In this paper, we investigated the effect of surface charge of the functional bio-interface of a nanowire field effect biosensor on the conductance of the nanowire through finite element calculations. The biosensor under consideration consisted of a silicon nanowire with radius of 15 nm surrounded by a 3-nm oxide layer, and it is surrounded by a 4 nm thick functional bio-interface layer. This whole system is immerged in an electrolyte and each of the layers was treated as a continuum medium characterized by the corresponding dielectric constant. First, the distribution of the electrostatic has potential in the narrower due to the surface charge. Then, the conductance of the nanowire was computed though integrating the effect of the potential on the charge carriers within the narrower and it is computed using Poisson equation with Boltzmann statistics. Finite element calculations showed the nonlinear dependence of the nanowire conductance on the bio-interface surface charge. The conclusion of the paper is the electrical potential distribution was found by solving these approximated equations.
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