AVS 47th International Symposium
    Material Characterization Tuesday Sessions
       Session MC-TuP

Paper MC-TuP28
Challenges in Insulator Surface Analysis

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: M. Reichling, Universit@um a@t M@um u@nchen, Germany
Authors: M. Reichling, Universit@um a@t M@um u@nchen, Germany
C. Barth, Universit@um a@t M@um u@nchen, Germany
M. Huisinga, FU Berlin, Germany
R. Lindner, FU Berlin, Germany
Correspondent: Click to Email
The application of high end ultraviolet optical materials as required for next generation optical lithography is extremely demanding in terms of preparing defect free surfaces. We report about major progress in insulator surface analysis with respect to both, characterizing the electronic and geometric surface structure. This is exemplified for crystals with the fluorite structure (CaF@sub 2@, SrF@sub 2@, BaF@sub 2@) that are important materials for advanced ultraviolet optical applications. Results from highest sensitivity ultraviolet photoelectron spectroscopy revealing defect states are presented. Supported by additional evidence from ultrafast laser spectroscopy, we demonstrate that for any preparation there are occupied and unoccupied states throughout the band gap where the density of states strongly decreases with energy above the valence band edge. The sources of the band gap states as well as their implications for optical absorption in the ultraviolet are discussed. We recently presented atomic resolution in imaging defects on a fluoride surface with scanning force microscopy in the ultra-high vacuum.@footnote 1@ With such measurements and controlled gas exposure we can show that chemical interactions between gas molecules and surface defects play a major role in the degradation of surfaces exposed to air. We, furthermore, demonstrate that it is now possible to resolve not only defects on terraces of cleaved surfaces but also features like step edges and kinks with atomic resolution and that we are able to locate positions of individual ions and vacancies along steps. We present recent results where we resolved individual atoms in regular nanometer-sized surface clusters that are a result of cleavage. @FootnoteText@ @footnote 1@ M. Reichling, C. Barth, Scanning force imaging of atomic size defects on the CaF@sub 2@(111) surface, Phys. Rev. Lett. 83(4), 768 (1999).