Strain, stress and structural analysis of manganite and cobaltate thin films

Due to their unusual magnetic and electronic properties complex oxides like Manganites and Cobaltates are promising materials for new functionalities and novel applications. For example, these oxides reveal interesting thermoelectric properties and persistent resistance changes which might be used for energy conversion and data storage. However, these properties are extremely sensitive with respect to crystallographic disorder and strain commonly present in thin films. As model systems we have prepared thin films of Pr1-xCaxMnO3 (PCMO) and Pr1-xCaxCoO3 by an ion beam sputtering technique. The strain-stress relation with respect to the exact deposition condition is analyzed by combining an in-situ measurement of the substrate bending (Stoney equation) and ex-situ X-ray investigations (Sin2 Ψ -method). This allows to estimate the elasticity modulus and the Poisson ratio of PCMO to about E=94 GPa and ν=0.25. For analysing the early stage of film growth with respect to crystallographic order and surface roughness RHEED measurements are performed during the film growth. Extending both in-situ analytical techniques (stress measurement, RHEED) to high-temperature deposition processes, first results concerning the temperature dependence of stress development and film growth are presented.