| QSA9
15th. - 19th. July 1996, University of Surrey
Meeting Report (Reporter - Jim Castle)
QSA - Quantitative Surface Analysis - has been held biennially
without break, and this was the third to be held on the campus of Surrey University in
Guildford, UK. The conference series was an initiative of the National Physical
Laboratory, the UK’s premier laboratory in standards and measurement, who have
organised and sponsored all previous meetings. QSA9 was the first in the series to be
organised and fully sponsored by a university but, in doing so, Surrey remained true to
the traditions of this series, which is the pre-eminent forum for exchange of views on
quantitative aspects of surface analysis. The meetings are small and with a workshop
atmosphere which befits such a tightly focused activity.
This meeting was attended by some 110 delegates, of whom 60 were from
overseas, including strong representation from the USA and Japan as well as from
Australia, Canada, South Africa, Korea and our neighbours in the EU and the rest of
Europe. These numbers just ensured the financial success of the meeting and gave an
excellent basis for the week-long discussions. A small exhibition was supported by many
familiar names in instrumentation for surface science. A novel feature was the holding of
a conference session in which papers on data analysis were presented using interactive
computer displays projected onto the large screen. This was a real success, judged by a
sticking factor - the very large number of delegates remaining late into the evening which
the bar was open.
The highlights of the social events were the outing to Hampton Court
Palace, the home of Henry VIII, and the conference dinner at the nearby Losley House,
where we had the pleasure of the company of the Vice-Chancellor and his wife. The after
dinner talk was, in the tradition of QSA, on a relaxed topic of technical interest to us
all. It was given by Prof. Richard Palmer entitled "Seven Wonders of a Small
World" and was a fascinating review of his candidates for a present day set of
nano-wonders to rival the macro-wonders of the ancients. During this Dinner, Prof. (sic.)
Robert Wild, chairman of the UK Electron Spectroscopy Users Group, presented their Riviere
Prize to Prof. David Briggs.
The local committee responsible for the organisation consisted of Prof.
James Castle and Dr. John Watts representing the university and Dr. Martin Seah of the
NPL. Mrs. Penny Briggs was a very able conference secretary.
There were, in total, eleven invited speakers:
Prof. Peter Sherwood, Kansas State University, USA,
opened the session on XPS with a review on "The Quantitative Correlation of Peak
Structures with Chemical Structure in XPS". In his talk, he demonstrated how XPS can
supply information on the chemical state of the surface examined. He showed the
complementarity of the core and valence parts of the spectrum and illustrated many
features by relating them to the outcome of a variety of molecular orbital calculations,
including those of band structure and clusters.
Dr. Cedric Powell, NIST, Gaithersburg, USA, spoke on
"Recent Progress and Remaining Problems in Quantitative Surface Analysis by AES and
XPS". He reviewed the areas in which significant progress had now been made,
including calibration of intensity and energy scales, improved knowledge of electron
elastic scattering effects, improved methods for determining the background for inelastic
scattering and better knowledge of electron inelastic mean free paths. In AES, he pointed
to the improvements in algorithms for topographic correction of maps and to the growing
availability of data bases. Further progress was needed in matrix and chemical effects.
Prof. Peter Weightman, University of Liverpool, UK,
opened the session on Auger Electron Spectroscopy with a discussion/review of
Matrix/Environmental Effects on AES and XPS Peaks. His comments on the importance of
matrix and alloying effects on peak profiles was very apposite in view of the
identification of a need for this work by Powell.
Dr. M. P. Seah, National Physical Laboratory, UK,
introduced the session on quantification, spoke on "Differences in the Intensity
Establishment in AES and XPS, pointing to the fact that although most terms used in these
two spectroscopies were interchangeable in definition, this was not so in practical terms
because of the different modes of operation used in their use in analysis. He exampled
background removal, by a Shirley or Tougaard background intensity profile in XPS and by
means of differentiation in AES. There were other similar examples of differing usage but
also different areas which still needed attention for full portability to be established
between different instruments. He cited here angular anisotropy in XPS and backscattering
corrections in AES.
Dr. Wolgang Werner, TU Vienna, Austria, an invited
speaker in the same session, gave his lecture on "A Partial Intensity Approach in
Quantitative Surface Analysis". He argued the case handling a large variety of
processes in routine surface analysis, showing that it was possible to account for depth
and energy dependent elastic and inelastic scattering, surface roughness, surface
excitations, anisotropic source distribution and signal excitation. All of these will
depend on sample structure but, in principle, will allow the entire spectrum compositional
depth profile to be obtained from the experimental energy and angular distribution.
Prof. Jim Castle, University of Surrey, UK, one of the
home speakers, also addressed the theme of obtaining a total view of the sample in his
talk on "Coding Knowledge into Rules for an Expert System". He referred to the
manner in which much information was hidden in the mean analysis supplied by the typical
data system and showed how, by use of a rule set based on well understood principles in
electron spectroscopy, one could easily draw out from the spectra information of a type
which would be useful to a client or non-expert making use of the spectroscopy as a
service.
Dr. H. Salemink, IBM Zurich Research Laboratory, was
invited to open the session on probe microscopy with a review of opportunities for
"Quantitative Analysis with Scanning Probe Microscopy". His talk opened our eyes
to the exciting possibilities for probe analysis on the atomic scale. In particular, he
demonstrated how the averaging of line rows which takes place in analysis in the TEM lead
to a misleading impression of atomically flat interfaces which STM was now exposing. He
illustrated this and the basis of tunnelling spectroscopy with a large number of excellent
examples.
Prof. Joseph Gardella, SUNY at Buffalo, USA, gave an
excellent talk on "Quantitative Analysis of Polymer Surfaces by SIMS. He referred to
advances made in his laboratory by use of well characterised thin film samples - based on
adsorption or L-B film methods. Project areas developed from this approach included
studies of the kinetics of degradation of biodegradables in which the change in molecular
weight with time was derived directly from static SIMS spectra.
Dr. Birgit Hagenhoff, Philips Research, The Netherlands,
produced a nicely complementary lecture on "Quantification in ToFSIMS of
Organics" as her invited address. She reviewed the progress made in static SIMS since
its inception in the 70s. She showed that when, against the perceived wisdom,
quantification using ToFSIMS is attempted, the results are astonishingly good.
Pr. K. Wittmaack, GSF ISS, Germany, provided the
contrast with static SIMS in his lecture on "Quantitative Data in Ultra-High
Resolution Depth Profiling: Theory and Practice", dealing with dynamic SIMS and SNMS.
His review dealt with the important instrumental and technique developments which have
made this the analysis method of choice for those concerned with depth profiling. His
expert’s eye view did not stop at advances but pointed also to as yet unresolved
problems, such as preferential sputtering.
Dr. Roger Webb, University of Surrey, UK, the other
home speaker, rounded of the session on dynamic SIMS with a talk, "TRIM Codes and
their Derivatives Explained". This provided a fulsome review and tutorial for all of
us concerned with the steady development of this simulation approach to depth profiles.
His talk provided the intended bridge to the back-to-back conference held the following
week, COSIRES-96, which some of the QSA delegates were to attend. |
