Regensburg 2010 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 51: Electronic Properties I

MM 51.3: Vortrag

Donnerstag, 25. März 2010, 10:45–11:00, H5

Optical and electrical characterization of Al doped Zinc oxide nanoporous films prepared via sol-gel method — •Babak Nasr, Subho Dasgupta, Robert Kruk, and Horst Hahn — Karlsruhe Institute of Technology (KIT) GmbH,Institute of Nanotechnology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

Highly transparent and conducting ZnO films doped with different Al concentration prepared via sol-gel method. In this study one of the most important deposition parameters, heat ramping at pre-heat-treatment step, was investigated to grow high porous thin films in high surface area applications. It was found that high porosity is obtainable by fast heat ramping of the gel films. In addition the optical and electrical properties of Al doped ZnO films as a function of carrier concentration was studied using UV-Vis, FTIR spectroscopy, and four points measurement. The films were all transparent in visible range and had a sharp absorption around 380 nm. A blue shifts of the absorption edge respect to undoped ZnO has been observed as a function of the carrier concentration up to 2 at.% Al doping due to Burstein-Moss effect. Strongly resonance absorption at plasma frequency in near infra red region led to calculation of carrier concentration. These investigations were complemented by photoconductivity measurement to understand the impact of surface states in electronic structure of the films. Among different doped films with atomic ratio of 0.5 to 4 with increments of 0.5 the systems with 1.5at.% to 2at.% show the lowest resistivity and widest optical band gap.