Strontium titanate (SrTiO3, STO) is an oxide of titanium and strontium exhibiting a perovskite structure. It has interesting and partly unique material properties. It is used as substrate for growth of oxide-based thin films and high-temperature superconductors.
STO forms surfaces that show a layered structure. The thickness of individual layers is in the range of a few Angstrom. Atomic force microscopy is an ideal tool to image and measure these structures.
Topography of a strontium titanate (STO) sample. The sample clearly shows the typical layer structure STO. Here, the layers are not perfectly smooth, but exhibit residual roughness of approx. 125 pm (RMS). This is caused by a non-ideal termination process during the preparation of this STO sample.
The left graph shows the profile of the image shown above along a line extending from the top left to the bottom right corner of the imaged area. The profile also clearly shows the layered structure of the sample and reveals step heights of approx. 4 Å. Similarly in the right panel, the height distribution histogram of the image above clearly shows approx. 4 Å-spaced peaks for the different layers of the sample.
All measurements were performed using a Nanosurf Flex-Axiom system equipped with BudgetSensors Tap150 cantilevers. Images were processed using the MountainsMap SPM.
Nanosurf application note AN01107