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SSL Seminar Series 2001 No. 6
Title: Low Temperature Scanning Force Microscopy: Atomic Resolution
Imaging and Force Spectroscopy
Speaker: Dr Mark Lantz (Institute of Physics, University of
Basel, Switzerland)
Date: 7th March 2001
Time: 3:00 pm
Venue: Physics Conference Room S13, Mo1-15
Abstract
A low temperature scanning force microscope operating in an ultra
high vacuum environment was used to study the Si(111) 7x7 surface
at 7.2 K. Image quality comparable to that of the scanning tunnelling
microscope is demonstrated. The twelve adatoms and six rest atoms
in each unit cell are clearly resolved. In addition, the first direct
measurements of the short-range chemical bonding forces above specific
atomic sites will be presented. [1] The data is in good agreement
with first principles computations and indicates that the nearest
atoms in the tip and sample relax significantly when the tip apex
is within a few angstroms of the surface. Experiments with non-reactive
tips reveal atomically resolved images with surprisingly different
contrast from those obtained with a reactive tip. Careful analysis
of frequency versus distance curves clearly shows that the contrast
does not result from the formation of a covalent bond, however, atomic
resolution is still obtained. The physical nature of this interaction
mechanism will be discussed and compared to theoretical models.
[1] Lantz et al., Phys. Rev. Lett 84, 2642 (2000).
About speaker
Dr. Mark Lantz received BSc and MSc degrees in Electrical Engineering
from the University of Alberta, Canada and a PhD from Cambridge University
in the UK. Upon completion of his PhD, he worked for two years as
a research scientist in the area of scanning probe microscopy at the
Joint Research Center for Atom Technology in Tsukuba, Japan. Since
leaving Japan in the spring of 1999, he has conducted research in
the field of low temperature scanning force microscopy at the Institute
of Physics, in the University of Basel, Switzerland. |
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