Dresden 2014 – scientific programme

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DS: Fachverband Dünne Schichten

DS 30: Focus Session: Emerging oxide semiconductors II (jointly with HL, DF, O)

DS 30.9: Talk

Wednesday, April 2, 2014, 17:45–18:00, POT 081

Electrical properties of In2O3 single crystals: distinction between surface and bulk conductivity — •Klaus Irmscher, Mike Pietsch, Wolfram Troeder, and Zbigniew Galazka — Leibniz-Institut für Kristallzüchtung, Berlin

Transparent semiconducting oxides such as In2O3, SnO2 or ZnO have the tendency to form surface electron accumulation layers. The highly conductive surface layers may have strong implications in the emerging field of transparent oxide electronics. For instance, the implementation of active elements like Schottky diodes depends on whether the accumulation of electrons at the surface can be suppressed in a controlled manner. Investigations on the origin of the surface electron accumulation in In2O3 were hitherto performed on thin crystalline films. Here, we present temperature dependent Hall effect measurements of melt-grown In2O3 bulk single crystals. The samples had electron concentrations between 10^16 and 10^19 cm-3 at room temperature depending on post-growth annealing conditions. The temperature dependent electron concentrations measured from 15 to 750 K show clear contributions due to surface electron accumulation. To differentiate between bulk and surface proportions the data evaluation is based on a two-layer model. This enables a clear attribution of donor concentration changes due to sample annealing under oxidizing or reducing conditions to surface-near and bulk regions, respectively. We discuss the possible influence of oxygen vacancies, hydrogen donors and surface adsorbates.