Surface analysis of self-assembled ZnO NiO nanostructures

Abstract In this work we have successfully discriminate NiO from ZnO materials in a pillar-matrix nanostructured thin film using various surface microscopy techniques. In order to do so, we have deposited a ZnO NiO co-deposited thin film with a single target composed of ZnO 0.8 NiO 0.2 grown on SrTiO 3 :Nb substrate by pulsed laser deposition. Scanning probe microscopy and scanning electron microscopy techniques reveal that the surface is composed of wide and well-spaced topographical nanopillars with various size embedded in a flat matrix. In order to fully discriminate the nanopillars from the matrix, the nanoscale piezoelectric and electrical properties of the sample have been analyzed by Piezoresponse Force Microscopy and Conductive-Atomic Force Microscopy. These techniques reveal that the flat matrix is piezoelectric, semiconducting and correspond to ZnO. Whereas the nanopillars are non-piezoelectric, exhibit a low current semiconducting behavior and correspond to NiO. Local I-V measurements confirm the low current semiconducting behavior for the NiO nanopillars and the semiconducting behavior for the ZnO matrix and well agree with the Scanning Probe Microscopy images. In order to investigate the charge transport mechanism of the NiO pillars and the ZnO matrix system, the local I-V measurements are compared to the theoretical band diagram models of our metal/semiconductor/metal systems.