Leitfähigkeitsuntersuchungen an ZnO Nanostäben mittels Rasterkraftmikroskopie

Translated title of the contribution: Conductivity investigation on ZnO nanorods using atomic-force microscopy

Lin Wang

Research output: ThesisDiploma Thesis

82 Downloads (Pure)

Abstract

Due to its imaging principle, Atomic-Force Microscopy (AFM) allows quantitative morphological characterization of surface nanostructures. Furthermore, using a conductive probe, AFM enables investigation of electrical properties on the nanometer scale. Here, the first capability of AFM is applied to investigate morphological properties of upright standing ZnO-Nanorods (NRs), whereas conductive atomic-force–microscopy (C-AFM) is employed to perform conductivity measurements on these structures. ZnO has many excellent and unique properties, which are interesting from a scientific and technological point of view. ZnO exhibits piezoelectric properties, ultraviolet (UV) emission, conductivity and transparency in the optical range, bio-security, a high exciton binding energy, etc. As semiconductor, due to its large bang gap of 3.37 eV, it is an interesting material for optoelectronic applications in the near UV spectral range. For the application of ZnO NRs, it is necessary to control the rod position, direction, and shape. Topographical information on three-dimensional shape, average diameter, and height fluctualtions of upright standing ZnO-nanorods were obtained. The morphologies of the ZnO NRs are strongly dependent on substratetype (Si(100), FTO) and growth methods. The typical average true diameter of the NRs fabricated by thermal evaporation (TE) is in the range of 200 nm to 370 nm and is much larger than that obtained with hydrothermal growth (HT) which is around 100 nm. The height variation is between 100 nm and 820 nm for TE NR samples & between 40 nm and 220 nm for HT NRs. C-AFM with a conductive probe was used for investigating the local electrical conductivity of individual NRs. For a sufficiently high applied force between sample and tip, a stable Schottky contact forms. The nanocontact is characterized by two important parameters: the ideality factor and the Schottky-barrier height. Both parameters could be calculated from current-voltage measurements, and they depend on sample type and contact force. The barrier height of the TE ZnO NRs is with (0.15±0.01 eV) smaller than the barrier height of the HT ZnO NRs (0.23 eV). The Schottky diode between tips and top facets of the ZnO NRs are not ideal because the obtained ideality factors are greater than 1 for all samples investigated. Generally, the results demonstrate a high conductivity of the ZnO NRs.
Translated title of the contributionConductivity investigation on ZnO nanorods using atomic-force microscopy
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
  • Teichert, Karl Christian, Supervisor (internal)
  • Kratzer, Markus, Co-Supervisor (internal)
Award date30 Mar 2012
Publication statusPublished - 2012

Bibliographical note

embargoed until null

Keywords

  • ZnO
  • zinc oxide
  • conductivity
  • nanorods
  • atomic-force microscopy
  • AFM

Cite this