For the development of ultra sensitive electrical bio/chemical sensors based on nanowires, the influence of the liquid environment such as the pH value, ionic strength of the solution, and the surface charge on the electron transport has to be understood. For this purpose, we implemented a modified Poisson-Boltzmann theory into a previously-developed multiscale model [1], which combines two models on different scales: (1) the finite element method for the calculation of electrostatic potential and (2) a Landauer transport approach based on non-equilibrium Green functions formalism to calculate the charge transport through the device. We investigated the changes of the electric potential and transport characteristics due to the ionic concentration, the pH value, and surface charge densities, systematically. Using this model, we could reproduce the reduction of sensitivity of the sensors due to the screening effect from the electrolyte.

[1] D. Nozaki, J. Kunstmann, F. Zörgiebel, G. Cuniberti Nanotechnology 22, 325703 (2010).