on the IUVSTA Workshop on
Photoelectron Spectroscopy: from Physics to Data
The workshop, similarly to the very successful previous IUVSTA Workshop on Auger Spectroscopy (Saint Pierre de Chartreuse, 1995) brought together experts in the field of X-Ray Photoelectron Spectroscopy (XPS) with the aim of reviewing and discussing recent developments and trends as well as perspectives for the future concerning the fundamentals and applications of the XPS method, from the point of view of the analytical use and reliability of the data obtained by surface analysis using XPS. The scientific field and scope of the Workshop falls within the area of activity of the Applied Surface Science Division of the IUVSTA. Attendance of the Workshop was ensured in the first instance by invitation and many of the best and most active scientists of the field participated in the meeting. The 45 participants of the Workshop were drawn from 16 countries (including 15 member countries of IUVSTA) of Europe, North-America, Asia and Australia.
The scientific programme of the meeting was developed by the Scientific and Program Committee, chaired by J.E. Castle and L. Kövér and including M.-G. Barthés, J.T. Grant, C.J. Powell, M.P. Seah, J. Végh and K. Yoshihara as members, while the Local Organizing Committee, with L. Kövér (Chairman), E. Bene, I. Cserny and J. Végh as members, was responsible for most local matters of organization and for ensuring appropriate conditions for the meeting. Registration, contracts for accommodation, meals and transportation were organized by the Roland Eötvös Physical Society.
The main objectives of the participants-scientists and analysis with interests ranging from the basic theory to practical applications of XPS-were to:
The structure of the scientific program based on sessions of 1,5h each including 17 invited reviews on special topics as well as extended and intense scientific debate and discussion in each session between the experts present. The sessions were moderated by selected experts of the particular topics. In addition to these sessions, two after dinner meeting were organized, a panel discussion on the impact of XPS on solving practical problems of industry, and a software demonstration. At the end of the meeting the closing summary of the technical content of the meeting was provided by Professor J.E. Castle acting as rapporteur (please, find the written version of the summary enclosed). Attached please find a copy of the scientific program of the Workshop and the list of participants. Although no proceedings of the Workshop will be published, a detailed Summary of the contributions and discussions is planned to be submitted for publication in the journal Surface and Interface Analysis, similarly to the previous AES Workshop.
The venue of the meeting was the Hotel Epona lying in the heart of the Hortobágy National Park (close to Debrecen), a boundless plain ("puszta") rich in natural resources, historical and etnographic traditions. A unique resort of Eastern Hungary, the four star hotel in the Epona Riding Village provided full comfort accommodating the delegates and ensuring a quiet place for the conference. A social occasion was also organized for the participants including a visit to the famous Rákóczi wine-cellar in Tokaj.
Debrecen, 24. 06. 1999.
In making this report the impressions and notes made of a very full week of discussion have been extensively abridged and suitably grouped with the intention of giving an overall impression of a week long activity. The report was timed to be given in a 30minute presentation immediately following the final scheduled talk and has not been modified in this written version which is a summary of the viewgraphs used in making the presentation. This report will be fully augmented in good time by the authors abridged versions of the papers delivered at the meeting.
PROGRESS IN RECOGNITION OF CHEMICAL STATE
Weightman first gave a review of the frozen orbital method. He showed that many approximations are now replaced by full calculation of e.g. the Dirac-Fock code. Calculations use determinants, instead of products, to mix the wave functions of appropriate orbitals, correlation effects are included by including the core hole in differing orbitals. Typical calculation for Ar gives BEs correct to 1% on ls, 4% on 2s, 25% on 3s. The differences arise from static relaxation effects, and correlation associated with dynamic relaxation mobile holes. The error in calculation of BE is mirrored in calculation of transaction rates and hence intensities.
Charlier showed exciting results for Cls calculation using the Density Functional Theory of Chong a development of the unrestricted generalized transition state theory. This theory enables relaxation in free organic molecules to be introduced into the calculation by use of partial charge (2/3e) in ionised bonds. Free molecules give spectacular agreement with experimental values. Absolute average deviations between measured and calculated 0.11 eV are found for a set of 20 molecules. The method extended to adsorbed molecules (g aminotriethoxysilane) and to their reaction with H2CO3.
Sherwood showed how X-ray excited valence band spectra gave unique finger print identification and that these could be supported by calculations. Monochromatic sources were of value to remove confusing influence of the a 34 peak.
strong 3d contribution
An example was given in which spectrum subtraction enabled Ti alcoxide to be observed at a buried interface.
Moretti - reviewed the history and use of the Auger parameter and especially of the chemical state diagrams. This can be used to obtain the extra-atomic relaxation energy - well known final state. In a new contribution to the use of such diagrams he showed that if the data were charge-referenced before plotting then lines representing initial state effects could be drawn on the chemical state diagrams. This approach was illustrated by work in zeolytes.
PROGRESS IN INTERPRETATION OF THE ELECTRON TRANSPORT STEP
SIMULATION OF SPECTRUM BACKGROUND
A comparison of calculation with known structure of Au/Ni sandwiches showed that determination of thickness of a buried layer to within a 15% error.
Cu Ag Au
C can all be used as standards.
Pireaux introduced a paper by Cazaux
gives 20 nm resolution and XPS (!) examination of :