Application of X-ray reflection interface microscopy to thin-film materials

New X-ray imaging techniques with excellent spatial resolution are under development for investigating surface and interface structures. X-ray reflection imaging microscopy (XRIM) applies full-field imaging to a specularly reflected X-ray beam from a surface or interface. This technique uses a zone plate objective lens to spatially resolve the reflected X-ray intensity and, by exploiting phase contrast, allows steps or terraces to be directly visualized. Thickness fringes caused by interferences in crystalline thin films grown on single-crystal substrates are observed near Bragg peaks and also carry information related to the termination of the film at either the surface or the film–substrate interface. We have applied the XRIM technique to image X-ray intensity along thickness fringes in complex oxide thin-film systems such as SrRuO3 on SrTiO3, EuTiO3 on DyScO3, and Bi2O3 on SrTiO3. Measurements of the contrast variations in the images as a function of momentum transfer, Q, allow features to be identified as steps/terraces, or attributed to film inhomogeneities. Using both the Q-resolution and the excellent spatial resolution of the XRIM technique, images of fabricated systems with lateral structures are demonstrated.