Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 63: Posters: Scanning Probe Methods

O 63.12: Poster

Mittwoch, 2. April 2014, 17:30–21:00, P2

Construction of a low-temperature STM for luminescence spectroscopy — •Hanna Fedderwitz, Boris Groß, Hendrik Sträter, and Niklas Nilius — Carl von Ossietzky Universität Oldenburg

Luminescence spectroscopy stimulated by electrons of an STM tip has recently been used to analyze the nature of point defects in ZnO films (1). The approach enabled a spectral identification of O and Zn vacancies with 100nm spatial resolution. These limits were given by the need to produce a finite number of electron-hole-pairs in the oxide band gap via impact of energetic tip-electrons. The required electron energy was determined to be 100eV, too high to map the optical response with true nm resolution and without damaging the oxide surface.

To overcome these limitations, we have developed a new scanning tunneling microscope suitable for low-temperature luminescence measurements. The setup is based on the beetle design, but uses a tapered and metal-coated optical fiber as sensor tip. The microscope is surrounded by a parabolic mirror for efficient photon collection. Our setup enables an all-optical characterization of sample surfaces, in which photons are either injected into or collected from the tip-sample junction via the fiber tip. The tip-sample distance is controlled by the STM-feedback loop, which also allows us to probe the sample topography with atomic resolution. The target application for our new setup is photoluminescence spectroscopy on thin dielectric films as used in photocatalysis.

(1) Stavale, Nilius, Freund, J. Phys. Chem. Lett. 4, 3972 (2013)