59 research outputs found
Spatially mapping thermal transport in graphene by an opto-thermal method
Mapping the thermal transport properties of materials at the nanoscale is of critical importance for optimizing heat conduction in nanoscale devices. Several methods to determine the thermal conductivity of materials have been developed, most of them yielding an average value across the sample, thereby disregarding the role of local variations. Here, we present a method for the spatially resolved assessment of the thermal conductivity of suspended graphene by using a combination of confocal Raman thermometry and a finite-element calculations-based fitting procedure. We demonstrate the working principle of our method by extracting the two-dimensional thermal conductivity map of one pristine suspended single-layer graphene sheet and one irradiated using helium ions. Our method paves the way for spatially resolving the thermal conductivity of other types of layered materials. This is particularly relevant for the design and engineering of nanoscale thermal circuits (e.g. thermal diodes)
Large Conductance Variations in a Mechanosensitive Single-Molecule Junction
The appealing feature of molecular electronics is the possibility of
exploiting functionality built within a single molecule. This functionality can
be employed, for example, for sensing or switching purposes. Thus, ideally, the
associated conductance changes should be sizable upon application of external
stimuli. Here, we show that a molecular spring can be mechanically compressed
or elongated to tune its conductance by up to an order of magnitude by
controlling the quantum interference between electronic pathways. Oscillations
in the conductance occur when the stress built up in the molecule is high
enough to allow the anchoring groups to move along the surface in a
stick-slip-like fashion. The mechanical control of quantum interference effects
and the resulting large change in molecular conductance open the door for
applications in, e.g., a minute mechanosensitive sensing device functional at
room temperature.Comment: 23 pages, 6 figure
Author Correction: In-situ formation of one-dimensional coordination polymers in molecular junctions
Tunable quantum dots from atomically precise graphene nanoribbons using a multi-gate architecture
Atomically precise graphene nanoribbons (GNRs) are increasingly attracting
interest due to their largely modifiable electronic properties, which can be
tailored by controlling their width and edge structure during chemical
synthesis. In recent years, the exploitation of GNR properties for electronic
devices has focused on GNR integration into field-effect-transistor (FET)
geometries. However, such FET devices have limited electrostatic tunability due
to the presence of a single gate. Here, we report on the device integration of
9-atom wide armchair graphene nanoribbons (9-AGNRs) into a multi-gate FET
geometry, consisting of an ultra-narrow finger gate and two side gates. We use
high-resolution electron-beam lithography (EBL) for defining finger gates as
narrow as 12 nm and combine them with graphene electrodes for contacting the
GNRs. Low-temperature transport spectroscopy measurements reveal quantum dot
(QD) behavior with rich Coulomb diamond patterns, suggesting that the GNRs form
QDs that are connected both in series and in parallel. Moreover, we show that
the additional gates enable differential tuning of the QDs in the nanojunction,
providing the first step towards multi-gate control of GNR-based multi-dot
systems
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