AVS 52nd International Symposium
    Nanometer-Scale Science and Technology Wednesday Sessions
       Session NS-WeM

Paper NS-WeM4
Bridge Enhanced Nanoscale Impedance Microscopy

Wednesday, November 2, 2005, 9:20 am, Room 210

Session: Nanometer Scale Imaging
Presenter: L.S.C. Pingree, Northwestern University
Authors: L.S.C. Pingree, Northwestern University
M.C. Hersam, Northwestern University
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Bridge Enhanced Nanoscale Impedance Microscopy (BE-NIM) advances the ability to measure the impedance of individual nanoscale conductive pathways in a variety of materials. Similar to Nanoscale Impedance Microscopy (NIM),@footnote 1@ this technique concurrently monitors the magnitude and phase response of the current through a conductive AFM tip in response to an AC bias. By varying the frequency of the driving potential, the resistance and reactance of nanometer scale conductive pathways can be quantitatively determined. Previously, we have demonstrated the extreme accuracy of NIM on a variety of control systems, such as a set of gold nanowires connected to known impedances, resulting in concurrent current and phase images. In addition, we have performed NIM on 8 µm x 8 µm Organic Light-Emitting Diode (OLED) pixels, which exhibit enhanced negative capacitance.@footnote 2@ However, the effects of long-range electrostatic interactions impose a detection limit on NIM of ~1 pF. These interactions, or fringe capacitance, act as a capacitor in parallel with the sample/tip junction. BE-NIM minimizes the contribution of this capacitance by employing a LRC bridge that improves the detection limit to ~50 aF. This improved sensitivity has been demonstrated on metal-oxide-semiconductor capacitors ranging in size from 5 fF to 50 aF. The application of BE-NIM to other materials systems, such as carbon nanotube/polymer composites and sub-micron OLEDs, will also be discussed. @FootnoteText@ @footnote 1@ L. S. C. Pingree, et al., IEEE T. Nanotechnol., 4, 255 (2005).@footnote 2@ L. S. C. Pingree, et al., Appl. Phys. Lett., 86, 073509 (2005).