Some non-transition metal oxides with a full d-shell such as In₂O₃, ZnO, and SnO₂, have a band gap of the order of 3 eV (meaning they are optically transparent) and an s-like conduction band (which implies that they conduct quite well when they are slightly n-doped). The combination of these properties is as rare as it is useful: Transparent conductive oxides (TCOs) are needed in virtually any technology that combines light with electronics. Moreover, the conductivity of these materials changes easily when they are exposed to oxidising or reducing gases, a property which is richly exploited in chemical sensing. And, as is true for most metal oxides, also TCOs play a role in catalysis. Surfaces and interfaces are critical wherever these materials are used and we want to learn more about them.

The most common transparent conductive oxide to date is In₂O₃. For use in applications, In₂O₃ is usually doped with Sn and then called ITO (indium tin oxide). Apart from utilising it, e.g., in solar cells, it is also used for transparent electrodes of LCD screens and OLED displays, and as an active material in gas sensors. More recently, applied studies discovered In₂O₃ to be catalytically active in CO₂ reduction reactions, which is also of interest for surface science.

Due to the conductivity of In₂O₃ all surface science instrumentation can be applied - and we focus on STM, non-contact AFM, TPD and XPS (both laboratory and synchrotron sources).

We are currently investigating the In₂O₃(111) surface utilising single crystals and crystalline thin films (grown in house with PLD, see "Atomically Controlled Thin-film Growth"). This surface stands out for its large unit cell (1.43 nm, three-fold symmetric) and complexity of the atomic arrangement with a multitude of inequivalent oxygen and indium sites, combined with its remarkable structural stability (non-polar, no reconstruction but a relaxed bulk termination).