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@PHDTHESIS{Weiss:82751,
author = {Weiss, Christian},
othercontributors = {Tautz, Frank Stefan},
title = {{STM} beyond vacuum tunnelling: scanning tunnelling
hydrogen microscopy as a route to ultra-high resolution},
volume = {47},
address = {Jülich},
publisher = {Forschungszentrum Jülich, Zentralbibliothek},
reportid = {RWTH-CONV-143120},
isbn = {978-3-89336-813-6},
series = {Schriften des Forschungszentrums Jülich : Reihe
Schlüsseltechnologien},
pages = {II, 165 S. : Ill., graph. Darst.},
year = {2012},
note = {Zsfassung in dt. und engl. Sprache; Zugl.: Aachen, Techn.
Hochsch., Diss., 2012},
abstract = {Direct imaging is a fast and reliable method for the
characterization of surfaces. When it comes to small surface
structures in the size of the features e.g. in todays
computer processors, classical optical imaging methods fail
in resolving these structures. With the invention of the
scanning tunnelling microscope (STM) for the first time it
became possible to image the structure of surfaces with
atomic precision. However, the STM fails in resolving
complex chemical structures like e.g. organic molecules. The
lack of chemical sensitivity in STM images can be overcome
by the condensation of molecular hydrogen or deuterium in
the STM junction. Images recorded in the so-called scanning
tunnelling hydrogen microscopy (STHM) closely resemble the
chemical structure of different organic molecules. However,
the mechanism behind the contrast formation has not been
addressed so far. Here we show that the origin of the STHM
contrast is a single hydrogen (H2) or deuterium (D2)
molecule located directly below the tip apex that acts as a
combined sensor and signal transducer. Together with the tip
the gas molecule forms a nano-scale force sensor, comparable
to sensors in atomic force microscopy (AFM), which probes
the total electron density (TED) of the surface trough the
Pauli repulsion and converts this signal into variations of
the junctions’ conductance again via Pauli repulsion.
Other than the sensors in conventional scanning force
techniques, due to its size, the sensor of the STHM junction
is intrinsically insensitive to long-range forces, usually
limiting the image resolution. The insensitivity to
long-range forces results in a high image resolution, so
that even small changes in the TED leave a mark in obtained
STHM images. The resolution hereby reaches an unprecedented
level as can be seen by the direct imaging of local
intermolecular interactions like e.g. hydrogen bonds appear
with remarkable clarity in STHM images of organic layers.
Thus, besides the identification of chemical species of
different adsorbates, the STHM mode allows the study of
interactions between adsorbates which e.g. lead to their
self organization on the surface. Therefore, the STHM mode
may give important insight in the driving mechanisms behind
the formation and composition of matter on the atomic level.
However, the STHM mode, in which a single H2 (D2) molecule
probes the TED of the surface, is only one example of a
broader class of sensors. It is conceivable, that by an
appropriate choice of the molecule in the junction, other
surface properties can be imaged which are usually
inaccessible by other imaging techniques.},
keywords = {Molekül (SWD) / Rastertunnelmikroskop (SWD) /
Rastertunnelmikroskopie (SWD)},
cin = {134110 / 130000},
ddc = {530},
cid = {$I:(DE-82)134110_20140620$ / $I:(DE-82)130000_20140620$},
shelfmark = {71.20.Rv 6},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
urn = {urn:nbn:de:hbz:82-opus-42500},
url = {https://publications.rwth-aachen.de/record/82751},
}
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