Electrical Conductivity of Epitaxial SrTiO3 Thin Films as a Function of Oxygen Partial Pressure and Temperature
Abstract:SrTiO3 (100) epitaxial films with thicknesses of 3, 1 m, and 250 nm were prepared on MgO (100) substrates by pulsed-laser deposition. The electrical conductivities of the thin films were systematically investigated as a function of temperature and ambient oxygen partial pressure. This was made possible by using a specially designed measurement setup, allowing the reliable determination of resistances of up to 25 GΩ in the temperature range of 600°–1000°C under continuously adjustable oxygen partial pressures ranging from 10−20 to 1 bar. The capabilities of the measurement setup were tested thoroughly by measuring a SrTiO3 single crystal. The well-known characteristics, e.g., the decline of the conductivity with a slope of –1/4 under reducing conditions and the opposite +1/4 behavior in oxidizing atmospheres, are found in the log()–log(pO2) profiles of the epitaxial films. However, the p-type conductivity decreases, and the n-type conductivity increases with decreasing film thickness. This phenomenon is attributed to the charge carrier redistribution in the surface space charge layers. Owing to the high surface-to-volume ratio, the space charge layers play an important role in thin films.
Document Type: Research Article
Affiliations: 1: Institut für Festkörperforschung and Center of Nanoelectronic Systems for Information Technology, Forschungszentrum Jülich, 52425 Jülich, Germany 2: Institut für Schichten und Grenzflächen and Center of Nanoelectronic Systems for Information Technology, Forschungszentrum Jülich, 52425 Jülich, Germany
Publication date: September 1, 2006