X-Ray Analysis Looks Into LSCO Thin-Film Properties


X-Ray Analysis Looks into LSCO Thin-Film Properties

15 July 2014
 
Scientists have created 3D atomic images of lanthanum, strontium, cobalt and oxygen (LSCO) thin films by measuring incident x-ray energies. This has rendered insight as to why they have superior properties compared to bulkier objects made from the same material.
 
The research team, consisting of scientists from the Massachusetts Institute of Technology, Hebrew University (Israel), Argonne National Laboratory and Oak Ridge National Laboratory, made the breakthrough after conducting two rounds of analysis and combining the findings.
 
First, researchers performed Coherent Bragg Rod Analysis (COBRA) on two 4-nanometer LSCO thin films: one previously heated to 550 degrees Celsius to simulate an industrial setting, and another left in ambient temperature. By collecting diffraction intensities along ten reciprocal space objects the researchers were able to create a 3D structure of each layer, with elements with more electrons indicated by higher peaks on the map.
 
Then, to gain more information about the distribution of elements occupying the atomic space between layers, the scientists applied a second method: energy differential COBRA. This involves performing measurements on the space objects by varying the incident x-ray energies around the strontium K-edge at each reciprocal space point.
 
Combining the two methods, the scientists created a 3D atomic image and revealed that strontium clustered in the outer layers of the LSCO thin films; it was almost absent from the layers closer to the substrate. Because of that, thin films outperform bulk materials. A layer that has more strontium also has less oxygen, and therefore reacts more to ambient oxygen on its surface.