Berlin 2024 – scientific programme
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O: Fachverband Oberflächenphysik
O 63: Poster DS (joint session DS/MM/O)
O 63.23: Poster
Wednesday, March 20, 2024, 17:00–19:00, Poster B
In-situ Study of Surface Band-Bending in c-ZnO and its Effect on the Excitonic Dielectric Function — •Luis Rosillo Orozco1, Kurt Hingerl1, and Christoph Cobet1,2 — 1Zentrum für Oberflächen und Nanoanalytik, Johannes Kepler Universität, Linz, Austria — 2Linz School of Education, Johannes Kepler Universität, Linz, Austria
Semiconductors in air and in vacuum often have a band-bending near the surface caused by surface states capturing bulk charges or simply due to natural polarization in the case of polar materials, as is the case of Zinc Oxide. Nevertheless, when semiconductors are in contact with an electrolyte we can intentionally produce a surface dipole and create a space charge region (SCR) by adding another electrode in the solution and applying a voltage between the two.
Space charge regions have a big impact on the optical and electrical properties of semiconductors and, of course, semiconductor devices. Therefore, it is of high interest to understand the effects caused by them.
We present in-situ spectroscopic ellipsometry (SE) combined with electrochemical techniques to study the response of the discrete excitons and exciton-phonon complexes (EPC) to the inner electric fields produced near the semiconductor surface. Using mono-chromatic transients we are able to identify the flat-band potential. A semi-empirical optical model is developed to study the contribution of the surface band-bending to the total dielectic function for a range between 3.2 e.V. to 3.6 e.V.
Keywords: Ellipsometry; Dielectric function; Zinc Oxide; Electrochemistry; Excitons