The outermost atoms of a surface largely control processes such as growth, nucleation, poisoning,
and electron emission. A complication is that the composition of the outer atomic layer of a material
is generally fundamentally different from that of the atoms below this surface. These outer atoms
can preferentially and quantitatively be analyzed with Low-Energy Ion Scattering (LEIS). This has
opened many new applications for microelectronics, sensors, catalysis and anti-wetting.
Typical ion energies in LEIS are between 1 and 10 keV. At the higher energies the mass resolution
is better, but is the information still restricted to the outer surface? Matrix effects are relatively small
in LEIS, which facilitates a quantitative analysis.
LEIS is applicable to any type of sample that can be taken into vacuum. It is just as well suited for
the analysis of amorphous, insulating, extremely rough surfaces (supported catalysts) as for
conducting, flat single crystals. However, the theory to quantitatively predict the atomic sensitivities
of the elements falls short. Although in recent years significant progress has been made in the
understanding of ion neutralization and reionization, an accurate analysis of the surface
composition still requires well-defined reference materials. The start and some of the pitfalls we
encountered in the selection of practical references for such a database, will be discussed. It will
also be shown how the surface density of silanol groups on fused silica can be determined and how
the unique properties of LEIS were essential to solve various other practical applications.
More information about Dr. Hidde H. Brongersma
Hidde Brongersma studied both physics and chemistry at Leiden University, where
he also received his PhD. During his career he has worked at the interface of
physics and chemistry. After a postdoc at Caltech he joined Philips Electronics
where he was at the cradle of Low Energy Ion Scattering (LEIS). During his time at
Philips he directed research on the development of the compact disc, optical fibers,
and a variety of high-end glass applications. Parallel to his industrial career, he was
appointed as professor of chemistry at Leiden University. Later he joined the faculty
of physics at the Eindhoven University of Technology. This gave him the
opportunity to further develop the LEIS technique and apply it to solve problems in
a great variety of materials applications. He is (co-)author of 300 papers, editor of
2 books, holds patents on the compact disc, optical fibers and on LEIS. In
Eindhoven he directed research efforts on catalysis, polymers, III-V semiconductors and ceramics.
Brongersma received numerous awards, an honorary doctorate (TU Brno), an honorary professorship
(Imperial College, UK) and the prestigious Jacob Kistemaker price in physics. He started a successful start-
up company, Calipso BV, which was at the basis of the High-Sensitivity LEIS technique that is now further
developed and marketed by ION-TOF in Germany.