Vacuum Ultraviolet Scanning Photoelectron Microscopy, Instrumentation & Applications

Abstract: This thesis describes the design and characterisation of a vacuum ultraviolet scanning photoelectron microscope as well as results from studies of laterally inhomogeneous surfaces. The instrument utilises synchrotron radiation from an undulator at the 550 MeV storage ring at the MAX-laboratory. The beamline is comprised of a plane-grating monochromator with a Kirkpatrick-Baez objective and a grazing incidence ring shaped ellipsoidal focusing mirror. The instrument provides a focused monochromatic photon beam with a high flux (10E9-10E10 photons/second) and a narrow bandwidth (0.03-0.25 eV) in the energy range from 15-150 eV. The ellipsoidal mirror gives a final focus with a full width half maximum of 1.5 micrometer. The instrument is used for laterally resolved photoelectron spectroscopy and imaging of surfaces by detecting energy filtered photoelectrons. The thermally activated desorption of oxide layers on Si(100) has been studied for different initial oxide thicknesses. The oxide layers desorb inhomogeneously and gradually reveal areas of clean Si. The thin oxides (5-15 Å) desorb in irregular patterns while 300 Å thick oxides desorb through the formation of circular voids that expose the clean substrate and grow with annealing time. Core level spectra reveal Si and SiO2 on the surface while sub-oxides exist only in the interface layer. For gold overlayers on these Si/SiO2 surfaces the formation of silicide and the agglomeration of Au has been studied. In the superconducting material Ba(sub0.6)K(sub0.4)BiO(sub3) we find local variations in the photoemission intensity, especially in the valence band spectra. We find regions on the surface where valence band spectra show much better agreement with theoretical predictions than previous measurements over large areas have shown. By locally illuminating the surface with the intense zero order beam we induce a transition from the metallic to the dielectric state which we believe to be due to a small depletion of the oxygen content. For extended illuminations the Bi oxide decomposes leaving metallic Bi in the surface layer. Finally it is demonstrated how the instrument can be used to study buried interfaces in Si/Si(sub 1-x)Ge(sub x)/Si heterostructures and to reveal the extent of interdiffusion that has taken place during the growth process.