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HL: Halbleiterphysik

HL 9: Poster I

HL 9.24: Poster

Montag, 27. März 2006, 15:15–17:45, P3

Cathodoluminescence Study of Zinc Oxide Nanopillars in a Field Emitter-SEM — •Martin Schirra, Anton Reiser, Andreas Ladenburger, Rolf Sauer, and Klaus Thonke — Abt. Halbleiterphysik, Universität Ulm, D-89069 Ulm

Investigation of semiconductor nanostructures in a scanning electron microscope (SEM) requires a field-emitter (FE) type cathode for high spatial resolution. When apart from SEM images also cathodoluminescence (CL) shall be measured, one has to know and control the excited sample volume which limits the spatial CL resolution and, due to electron scattering, is mainly determined by the energy of the primary electron beam. We present a simple model to estimate the size of the excitation volume. Small excitation volumes require low acceleration voltages, which in turn demand short working distances in the FE-SEM. This is problematic, if the CL-signal is coupled out via mirror optics. Therefore we have developed a setup which uses UV transparent glas fiber optics. The system was tested by recording CL spectra of single ZnO nanopillars. A spatial resolution of 80nm at a spectral resolution better than 0.5meV was achieved. Recording extrinsic and intrinsic near bandedge CL features the crystalline quality, strain, defects, shallow dopant species and doping gradients along the pillar axis are assessed and the results are discussed.