3,279 research outputs found
Black phosphorus: narrow gap, wide applications
The recent isolation of atomically thin black phosphorus by mechanical
exfoliation of bulk layered crystals has triggered an unprecedented interest,
even higher than that raised by the first works on graphene and other
two-dimensional, in the nanoscience and nanotechnology community. In this
Perspective we critically analyze the reasons behind the surge of experimental
and theoretical works on this novel two-dimensional material. We believe that
the fact that black phosphorus band gap value spans over a wide range of the
electromagnetic spectrum that was not covered by any other two-dimensional
material isolated to date (with remarkable industrial interest such as thermal
imaging, thermoelectrics, fiber optics communication, photovoltaics, etc), its
high carrier mobility, its ambipolar field-effect and its rather unusual
in-plane anisotropy drew the attention of the scientific community towards this
two-dimensional material. Here we also review the current advances, the future
directions and the challenges in this young research field.Comment: Updated version of the perspective article about black phosphorus,
including all the feedback received from arXiv users + reviewer
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-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
Calibration of piezoelectric positioning actuators using a reference voltage-to-displacement transducer based on quartz tuning forks
We use a piezoelectric quartz tuning fork to calibrate the displacement of
ceramic piezoelectric scanners which are widely employed in scanning probe
microscopy. We measure the static piezoelectric response of a quartz tuning
fork and find it to be highly linear, non-hysteretic and with negligible creep.
These performance characteristics, close to those of an ideal transducer, make
quartz transducers superior to ceramic piezoelectric actuators. Furthermore,
quartz actuators in the form of a tuning fork have the advantage of yielding
static displacements comparable to those of local probe microscope scanners. We
use the static displacement of a quartz tuning fork as a reference to calibrate
the three axis displacement of a ceramic piezoelectric scanner. Although this
calibration technique is a non-traceable method, it can be more versatile than
using calibration grids because it enables to characterize the linear and
non-linear response of a piezoelectric scanner in a broad range of
displacements, spanning from a fraction of a nanometer to hundreds of
nanometers. In addition, the creep and the speed dependent piezoelectric
response of ceramic scanners can be studied in detail.Comment: 9 pages, 3 figure
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