Characterization of Electrical Properties of Suspended ZnO Nanowires Using a Nanorobotic Manipulation System Inside a Scanning Electron Microscope for Nanoelectronic Applications

Abstract

Electrical characterization of semiconducting oxide nanowires (NWs) is mostly performed using complex techniques, which necessitates a series of costly nanofabrication procedures. In this work, with the aim to provide a low-cost, feasible, facile, and reproducible approach for enabling the study of NW electrical properties, we report direct electrical measurements on individual and overlapped suspended zinc oxide NWs (ZnO NWs). We have succeeded in constructing both two- and three-terminal devices simply by employing tungsten (W) nanoprobes with the aid of a nanomanipulation system embedded inside a scanning electron microscope’s vacuum chamber. Stable contacts were established using the Joule heating effect and e-beam exposure at the junctions between the NW and the pre-cleaned W tips. P-channel field-effect transistor devices were achieved with an on–off current ratio of ∼101, a threshold voltage (>1.5 V), a transconductance of ∼16 μS, a sub-threshold swing of ∼220 mV/decade, and field-effect carrier mobility roughly estimated to be around 926.4 cm2/(V·s) after correction for contact resistances/optimization. The average resistivity of ZnO NWs was calculated to be ∼2.23 × 10–2 Ω·cm for NWs with diameters between 70 and 500 nm. Besides, we have demonstrated a contact resistance of ∼19.60 kΩ and a Schottky barrier height of ∼0.37 eV present at W/ZnO NW interfaces. The contact resistance between two overlapped ZnO NWs was estimated to be ∼283 kΩ, which is relatively higher than that offered between W/ZnO NWs. This work provides a solid experimental procedure to address true intrinsic electrical properties at metal/semiconductor interfaces, and our findings have potential applications in next-generation 3D suspended ZnO NW-based nanoelectronic devices.