Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Semiconductor nanomaterials have come into the focus of research due to their potential for electronic and optoelectronic applications. Their properties strongly depend on their size, morphology, and dimension. In this work, we concentrate on the electrical and optoelectric properties of individual nanorods (NRs) in arrays of upright standing ZnO NRs. ZnO is a wide band gap semiconductor with potential application in solar cells [1] and gas sensors [2]. The NRs under investigation were grown via thermal evaporation (TE) and via hydrothermal synthesis (HT) [3,4]. In order to investigate such small structures atomic force microscopy (AFM) based methods have been applied. We utilized conventional conductive atomic force microscopy (C-AFM) [5] and additionally realized a photo conductive atomic force microscopy (PC-AFM) [6, 7] setup for our measurements. Examination of the current-to-voltage (I-V) characteristics measured for the top and side facets of individual TE grown NRs yielded Schottky like behavior with different barrier heights and ideality factors for both facet types [8]. The PC-AFM measurements on the top facet of TE grown NRs revealed a clear photo-response upon illumination with white light. Additionally, persistent photo-conductivity could be observed, manifesting itself by a very slow recovery to the initial dark conductivity level after light is switched off. Comparison of the dark and illuminated I-V characteristics revealed an increase in p-type conductivity for the illuminated case. The results will be discussed referring to the current models.

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[8] I. Beinik, M. Kratzer, A. Wachauer, L. Wang, R. T. Lechner, C. Teichert, C. Motz, W. Anwand,
G. Brauer, X. Y. Chen, Y. F. Hsu, A. B. Djurišić, J. Appl. Phys. accepted .