Local Conductivity Measurements of Metal-Organic Layers By Conductive AFM on Micropatterned Electrodes Produced By Metal Polymer Blend Lithography

Abstract

The electronic characterization of thin metal-organic layers like SURMOFs is often difficult, since transport contributions in global measurements may be dominated by pin holes with direct electrical contact of top and bottom electrodes. In addition, these measurements average over a wide surface area and no local information can be derived. Using an AFM with a metalized tip, local measurements of the conductivity and I-V characteristics can be extracted. But these measurements have three important draw backs: (I.) the small contact area in the 20-nm-range restricts the range of measureable conductivity due to a limited sensitivity of the electronic amplifiers, (II.) the electric field underneath the AFM Tip is rather inhomogeneous and current contributions in-plane and off-plane are mixed and (III.) the contact area varies individually from tip to tip and with the applied force. With our approach of polymer blend lithography (PBL) we produce billions of small metal islands with diameters in the range of a few hundred nanometers up to a few microns with a simple process (Metal-PBL) [1]. These Islands serve as planar top electrodes, which we can address individually with the AFM-tip in a highly reproducible way. Using a set of AFM scans in the same region, a manifold of data sets concerning conductivity and I-V characteristic can be extracted, since many individual islands are measured simultaneously. 1.: Polymer blend lithography for metal films: large-area patterning with over 1 billion holes/inch2: C. Huang, A Förste, S. Walheim, and Th. Schimmel: Beilstein Journal of Nanotechnology 2015, 6, 1205–1211