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C2.4 (In1–xGax)2O3-based gas sensors



Overview of the research project:

Indium oxide (In2O3) is a transparent semiconducting oxide (TSO) exhibiting native n-type conductivity referred to as unintentional doping (UID), the origin of which has been attributed to oxygen vacancies and hydrogen impurities acting as shallow donors. In2O3 is a well-established material in industry in its highly conductive Sn-doped form (ITO) as a transparent contact in optoelectronic devices. Moreover, In2O3 has been studied for applications as the active material in conductometric gas sensors, which is closely related to the existence of a highly gas-sensitive surface electron accumulation layer (SEAL) observed as a downward band bending at the In2O3 surface.

This project aims at understanding and controlling the electronic and fundamental gas sensing mechanisms of cubic In2O3as well as their transition behavior towards Ga2O3 with increasing Ga-content of cubic (In1–xGax)2O3.


Major accomplishments expected:

  • Homoepitaxy of In2O3 by MBE

  • Growth of single-crystalline (In1–xGax)2O3 with varying Ga content by MBE

  • Control of the In2O3and (In1–xGax)2O3surface and bulk conductance

  • Understanding the effect of doping on the gas-sensitivity of In2O3 and (In1–xGax)2O3

  • Clarifying the role of oxygen vacancies in the electrical transport of In2O3and (In1–xGax)2O3


Collaboration with partners in the project:

  • In2O3 substrates from: project C3.1

  • Optical investigations by Ellipsometry and Raman spectroscopy: project C1.5

  • Samples for band parameters, phase formation: projects C1.2, C1.4

  • Samples for surface studies by STM: project C2.3


The Research Team


Alexandra Papadogianni
PhD student

Alexandra Papadogianni obtained her BSc in Physics from the University of Crete in 2015 and her MSc in Physics from the Freie Universität Berlin in 2017. She has been a member of the oxides group at the Paul-Drude-Institut für Festkörperelektronik since 2014. Her work is mostly focused on the plasma-assisted MBE growth of In2O3 and the subsequent electrical and structural characterization of the material for applications in gas-sensors.


Project lead

If you have queries about the project, please contact the PI:
Oliver Bierwagen, Paul-Drude-Institut




Logo Leibniz-Gemeinschaft

The Leibniz ScienceCampus GraFOx is a network of two Leibniz Institutes, two universities and one institute of the Max Planck Society. It is based in Berlin, Germany.


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Kai Hablizel

Paul-Drude Institut für Festkörperelektronik (PDI)
Leibniz-Institut im Forschungsverbund Berlin e.V.
Tel.: +49 30 20377-342




Prof. Dr. Henning Riechert, PDI

Scientific Coordinator:

Dr. Oliver Bierwagen, PDI
Dr. Martin Albrecht, IKZ