Observation of Structure of Surfaces and Interfaces by Synchrotron X-ray Diffraction: Atomic-Scale Imaging and Time-Resolved Measurements

The recent developments in synchrotron optics, X-ray detectors, and data analysis algorithms have enhanced thecapability of the surface X-ray diffraction technique. This technique has been used to clarify the atomic arrangementaround surfaces in a non-contact and nondestructive manner. An overview of surface X-ray diffraction, from thehistorical development to recent topics, is presented. In the early stage of this technique, surface reconstructions ofsimple semiconductors or metals were studied. Currently, the surface or interface structures of complicated functionalmaterials are examined with sub-Å resolution. As examples, the surface structure determination of organic semiconductorsand of a one-dimensional structure on silicon are presented. A new frontier is time-resolved interfacial structureanalysis. A recent observation of the structure and dynamics of the electric double layer of ionic liquids, and aninvestigation of the structural evolution in the wettability transition on a TiO2 surface that utilizes a newly designed timeresolvedsurface diffractometer, are presented.