Nanoscale heterogeniety and workfunction variations in ZnO thin films

Anirudh Sharma, M Untch, Jamie Quinton, Rudiger Berger, Gunther Andersson, David Lewis

    Research output: Contribution to journalArticle

    15 Citations (Scopus)

    Abstract

    Nano-roughened, sol-gel derived polycrystalline ZnO thin films prepared by a thermal ramping procedure were found to exhibit different work function values on a sub-micrometer scale. By Kelvin probe force microscopy (KPFM) two distinct nanoscale regions with work function differing by over 0.1 eV were detected which did not coincide with the nano-roughened surface topography. In contrast, a flat ZnO surface displayed a single, uniform distribution. Ultraviolet photoelectron spectroscopy (UPS) studies showed that the average workfunction across a flat ZnO surface was 3.7 eV while ZnO with a nano-roughened morphology had a lower workfunction of 3.4 eV with indications of electronic heterogeneity across the surface, supporting the KPFM results. Scanning Auger Nanoprobe measurements showed that the chemical composition was uniform across the surface in all samples, suggesting the work function heterogeneity was due to variations in crystallinity or crystal orientation on the surface of these thin films. Such heterogeneity in the electronic properties of materials in thin film devices can significantly influence the interfacial charge transport across materials.

    Original languageEnglish
    Pages (from-to)516-521
    Number of pages6
    JournalApplied Surface Science
    Volume363
    DOIs
    Publication statusPublished - 2016

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