| The field of ferroelectrics has been of great interest of late due to its technological potential in the field of computer memory. While there has been considerable study into the electrical properties of these materials, many details of the atomic-scale structure are as yet unknown.; In this work, the x-ray standing wave (XSW) technique was used to determine the structure of the (3 x 2) and (2 x 1) Sr/Si(001) sub-monolayer reconstructions, and an extension of the technique for thin films was used to probe the polarity of both as-grown PbTiO3/SrTiO3(001) thin films and switched Ag/Pb(Zr0.3Ti0.7)O3/SrRuO3/SrTiO 3(001) capacitor structures. For the Sr/Si(001) system, Sr was deposited at room temperature in a UHV environment, and surface structures were grown by annealing the Si substrate, desorbing the Sr to different coverages. The coverage measurements were compared to those found in the literature, and using XSW data combined with STM information from the literature, it was concluded that Sr occupies the cave site. The XSW method has been applied to thin films, using the weak reflections from the films themselves to generate a standing wave field. By observing the fluorescence signal from ions in the films, the structure of the films, in this case the polarity, can be probed. Epitaxial films of the ferroelectric perovskite PbTiO3 grown on SrTiO 3(001) by metalorganic chemical vapor deposition (MOCVD) were examined by the thin-film XSW method. For 100, 200 and 400 Å films, the films exhibited both high crystalline quality and a preference for unipolar growth. The 600 Å sample was of lower quality and contained domains of both up and down polarizations. The capacitor structures containing Pb(Zr 0.3Ti0.7)O3 as a switchable dielectric were electrically examined and then left in a known switched state. The electrical measurements revealed that the samples were strongly imprinted, showing a preference for one orientation. Thin-film XSW measurements revealed that the capacitors left in the preferred polarization state remained in that state, while one of the capacitors in the hard state had backswitched to the easy state. The thin-film XSW method successfully probed these systems in a non-destructive manner, in contrast to traditional electrical measurements. |
