Electrical Transport in Individual ZnO Nanorods Studied by Photo-Conductive Atomic-Force Microscopy

One-dimensional ZnO nanostructures exhibit technological potential for many device applications, like efficient low-cost ZnO nanorod-polymer solar cells [1]. Conductive atomic-force microscopy (AFM) is a valuable tool for nanometer-scale electrical characterization of such nanorods [2]. Here, we present a complementary study of electrical transport in individual upright standing ZnO nanorods (NRs) grown by thermal evaporation [4] using conductive AFM (C-AFM) and photoconductive AFM (PC-AFM) [5]. Initially, the electrical properties of the arrays of upright standing ZnO NRs were characterized using two-dimensional current maps measured at different bias voltages applied to the sample contact mode. Further, C-AFM was utilized to determine the local current-to-voltage (I-V) characteristics of the top and side facets of individual upright standing NRs. PC-AFM investigations reveal that I-V curves taken from a single upright standing NR under illumination appear more degraded with respect to the non-illuminated state. Using PC-AFM, we also observed persistent photoconductivity from a single ZnO NR. Both phenomena can be attributed to oxygen desorption/re-adsorption from the ZnO NR surface.
Supported by Austrian Science Fund FWF under project # P19636.
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