2,048 research outputs found
Carbon-fiber tips for scanning probe microscopes and molecular electronics experiments
We fabricate and characterize carbon-fiber tips for their use in combined
scanning tunneling and force microscopy based on piezoelectric quartz tuning
fork force sensors. An electrochemical fabrication procedure to etch the tips
is used to yield reproducible sub-100-nm apex. We also study electron transport
through single-molecule junctions formed by a single octanethiol molecule
bonded by the thiol anchoring group to a gold electrode and linked to a carbon
tip by the methyl group. We observe the presence of conductance plateaus during
the stretching of the molecular bridge, which is the signature of the formation
of a molecular junction.Comment: Conference Proceeding (Trends in NanoTechnology 2011, Tenerife
SPAIN); Nanoscale Research Letters, (2012) 7:25
Force-gradient-induced mechanical dissipation of quartz tuning fork force sensors used in atomic force microscopy
We have studied the dynamics of quartz tuning fork resonators used in atomic
force microscopy taking into account mechanical energy dissipation through the
attachment of the tuning fork base. We find that the tuning fork resonator
quality factor changes even for the case of a purely elastic sensor-sample
interaction. This is due to the effective mechanical imbalance of the tuning
fork prongs induced by the sensor-sample force gradient which in turn has an
impact on the dissipation through the attachment of the resonator base. This
effect may yield a measured dissipation signal that can be different to the one
exclusively related to the dissipation between the sensor and the sample. We
also find that there is a second order term in addition to the linear
relationship between the sensor-sample force gradient and the resonance
frequency shift of the tuning fork that is significant even for force gradients
usually present in atomic force microscopy which are in the range of tens of
N/m.Comment: 9 pages, 3 figures and supplemental informatio
Carbon fibre tips for scanning probe microscopy based on quartz tuning fork force sensors
We report the fabrication and the characterization of carbon fibre tips for
their use in combined scanning tunnelling and force microscopy based on
piezoelectric quartz tuning fork force sensors. We find that the use of carbon
fibre tips results in a minimum impact on the dynamics of quartz tuning fork
force sensors yielding a high quality factor and consequently a high force
gradient sensitivity. This high force sensitivity in combination with high
electrical conductivity and oxidation resistance of carbon fibre tips make them
very convenient for combined and simultaneous scanning tunnelling microscopy
and atomic force microscopy measurements. Interestingly, these tips are quite
robust against occasionally occurring tip crashes. An electrochemical
fabrication procedure to etch the tips is presented that produces a sub-100 nm
apex radius in a reproducible way which can yield high resolution images.Comment: 14 pages, 10 figure
Thickness dependent interlayer transport in vertical MoS2 Josephson junctions
We report on observations of thickness dependent Josephson coupling and
multiple Andreev reflections (MAR) in vertically stacked molybdenum disulfide
(MoS2) - molybdenum rhenium (MoRe) Josephson junctions. MoRe, a chemically
inert superconductor, allows for oxide free fabrication of high transparency
vertical MoS2 devices. Single and bilayer MoS2 junctions display relatively
large critical currents (up to 2.5 uA) and the appearance of sub-gap structure
given by MAR. In three and four layer thick devices we observe orders of
magnitude lower critical currents (sub-nA) and reduced quasiparticle gaps due
to proximitized MoS2 layers in contact with MoRe. We anticipate that this
device architecture could be easily extended to other 2D materials.Comment: 18 pages, 6 figures including Supporting Informatio
Approaching ultra-strong coupling in Transmon circuit-QED using a high-impedance resonator
In this experiment, we couple a superconducting Transmon qubit to a
high-impedance microwave resonator. Doing so leads to a large
qubit-resonator coupling rate , measured through a large vacuum Rabi
splitting of MHz. The coupling is a significant fraction of the
qubit and resonator oscillation frequencies , placing our system close
to the ultra-strong coupling regime ( on resonance).
Combining this setup with a vacuum-gap Transmon architecture shows the
potential of reaching deep into the ultra-strong coupling
with Transmon qubits
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