1. Technische
Universität Wien, Institut für Angewandte Physik, Wiedner
Hauptstraβe 8-10, A-1040 Vienna, Austria
2. National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, U.K.
3. National
ESCA and Surface Analysis Center for Biomedical Problems, Departments
of Chemical Engineering and Bioengineering, University of Washington, Seattle, Washington 98195-1653, United States
4. Materials
Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8370, United States