Ion-step method for surface potential sensing of silicon nanowires

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    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 similar to 12 mV. We show that this method can be used as an alternative method for surface potential sensing, making it less sensitive to drift.
    Original languageEnglish
    Pages (from-to)7890-7893
    Number of pages4
    JournalAnalytical chemistry
    Issue number16
    Publication statusPublished - 16 Aug 2016

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