title: Ion-Step Method for Surface Potential Sensing of Silicon Nanowires.
abstract: This paper presents a novel stimulus-response method for surface potential sensing of silicon nanowire (Si-NW) field-effect transistors. When an "ion-step" from low to high ionic strength is given as a stimulus to the gate oxide surface, an increase of double layer capacitance is therefore expected. Thus, a change of conductance through the Si-NWs is measured. The surface potential on the Si-NW gate is changed from negative for a bare SiO2 surface to neutral/positive when there is poly-l-lysine adsorption at certain pH, which also indicates a shift of point-of-zero charge pH after surface modification. This change is measured by a drop of current variation at the ion-step. The ion-step is performed to the Si-NW through a polydimethylsiloxane microfluidic chip with automatic sample switching. A reduction of the ion-step response from 2 nA to almost zero at pH 5.0 is observed by increasing the potassium ion concentration from 10 mM to 50 mM, which corresponds to a surface potential change of ∼12 mV. We show that this method can be used as an alternative method for surface potential sensing, making it less sensitive to drift.
authors.affiliation: Department of Mechanical and Electrical Engineering, Xiamen University , 361005 Xiamen, China.
authors.forename: Songyue
authors.initials: S
authors.lastname: Chen
authors.affiliation: MESA+ Institute for Nanotechnology & MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente , 7522NH Enschede, The Netherlands.
authors.forename: Jan W
authors.initials: JW
authors.lastname: van Nieuwkasteele
authors.affiliation: MESA+ Institute for Nanotechnology & MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente , 7522NH Enschede, The Netherlands.
authors.forename: Albert
authors.initials: A
authors.lastname: van den Berg
authors.affiliation: MESA+ Institute for Nanotechnology & MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente , 7522NH Enschede, The Netherlands.
authors.forename: Jan C T
authors.initials: JC
authors.lastname: Eijkel