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Module 3 – Atomic and Molecular Nanosystems
This module focuses on the area of nanomechanics and nanomagnetism. The following topics will be addressed:
- magnetic nanostructures, magnetic interfaces, single spin experiments
- dissipation and movement of clusters and molecules on surfaces and the role of internal degrees
of freedom
- nanostencil and atomic manipulations to bridge the gap
Magnetic nanostructures will be investigated by Magnetic Force Microscopy (MFM) and Magnetic Resonance
Force Microscopy (MRFM). The interface of antiferromagnetic and ferromagnetic layers will be studied to
determine the spin densities by MFM. Measurements of magnetic exchange forces are performed to explore
the ultimate limits of MFM and to map magnetic phenomena with single spins sensitivity and atomic
resolution. Relaxation times of small spin quantities, ultimately single electron and nuclear spins,
are explored by MRFM. The local environments of electron spins of irradiated silica will be changed by
patterning the surfaces. The exceptional possibility to perform subsurface imaging will be explored by
MRFM and MFM.
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(a) Stripe domain pattern of the ferromagnetic film after zero-field cooling to 7K.
(b) Domain pattern at 650mT. (c) At 800mT the ferromagnetic film is saturated.
The 30 times weaker contrast visible in (c) is generated by the uncompensated spins at the
interface between the ferromagnetic and antiferromagnetic film.
(d) At -440mT the original domain pattern is perfectly recovered.
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Another goal is to understand fundamental dissipation mechanisms of nanometer-sized objects.
Nanoclusters as well as single molecules will be moved by the action of the probing tip. The role of
internal degrees of freedom of the molecules will be addressed. Conformations of the molecules on
insulators, in particular in traps, will be investigated by probe microscopy and X-ray photoelectron
diffraction (XPD). Conformational changes are induced by tunneling and forces. Inelastic tunneling
spectroscopy is used on thin insulating films to excite internal degrees of freedom of molecules. The
influence of electrical fields on their mechanical properties, such as contact stiffness and dynamic
friction, will be investigated. Is it possible to excite resonances of nanometer-sized objects by
alternating electrical fields? How does the excitation of the resonances affect their frictional and
motional characteristics. These experiments are accompanied by theoretical simulations to understand
friction and to investigate the energetics of molecules in traps.
A novel tool is the nanostencil from IBM Zurich: Structures of 40nm are created with the nanostencil
under ultrahigh vacuum conditions. Atomic manipulations will be used to bridge the gap between the
nanostencil structures. Structures will be fabricated and used for scientific questions related to the
above two topics.
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Schematics of the Nanostencil system |
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