title: Electrical monitoring of polyelectrolyte multilayer formation by means of capacitive field-effect devices.
abstract: The semiconductor field-effect platform represents a powerful tool for detecting the adsorption and binding of charged macromolecules with direct electrical readout. In this work, a capacitive electrolyte-insulator-semiconductor (EIS) field-effect sensor consisting of an Al-p-Si-SiO2 structure has been applied for real-time in situ electrical monitoring of the layer-by-layer formation of polyelectrolyte (PE) multilayers (PEM). The PEMs were deposited directly onto the SiO2 surface without any precursor layer or drying procedures. Anionic poly(sodium 4-styrene sulfonate) and cationic weak polyelectrolyte poly(allylamine hydrochloride) have been chosen as a model system. The effect of the ionic strength of the solution, polyelectrolyte concentration, number and polarity of the PE layers on the characteristics of the PEM-modified EIS sensors have been studied by means of capacitance-voltage and constant-capacitance methods. In addition, the thickness, surface morphology, roughness and wettabilityof the PE mono- and multilayers have been characterised by ellipsometry, atomic force microscopy and water contact-angle methods, respectively. To explain potential oscillations on the gate surface and signal behaviour of the capacitive field-effect EIS sensor modified with a PEM, a simplified electrostatic model that takes into account the reduced electrostatic screening of PE charges by mobile ions within the PEM has been proposed and discussed.
authors.affiliation: Institute of Nano- and Biotechnologies (INB), Aachen University of Applied Sciences, Jülich, Germany. a.poghossian@fz-juelich.de
authors.forename: A
authors.initials: A
authors.lastname: Poghossian
authors.forename: M
authors.initials: M
authors.lastname: Weil
authors.forename: A G
authors.initials: AG
authors.lastname: Cherstvy
authors.forename: M J
authors.initials: MJ
authors.lastname: Schöning