377 research outputs found
NOTES ON THE LIST OF REPTILES OF JAVA
Abstract not availabl
Models for quantitative charge imaging by atomic force microscopy
Two models are presented for quantitative charge imaging with an atomic-force microscope. The first is appropriate for noncontact mode and the second for intermittent contact (tapping) mode imaging. Different forms for the contact force are used to demonstrate that quantitative charge imaging is possible without precise knowledge of the contact interaction. From the models, estimates of the best charge sensitivity of an unbiased standard atomic-force microscope cantilever are found to be on the order of a few electrons
Localized charge injection in SiO_2 films containing silicon nanocrystals
An atomic-force microscope (AFM) is used to locally inject, detect, and quantify the amount and location of charge in SiO2 films containing Si nanocrystals (size ~2–6 nm). By comparison with control samples, charge trapping is shown to be due to nanocrystals and not ion-implantation-induced defects in samples containing ion-beam-synthesized Si nanocrystals. Using an electrostatic model and AFM images of charge we have estimated the amount of charge injected in a typical experiment to be a few hundred electrons and the discharge rate to be ~35±15 e/min
Charging of single Si nanocrystals by atomic force microscopy
Conducting-tip atomic force microscopy (AFM) has been used to electronically probe silicon nanocrystals on an insulating substrate. The nanocrystal samples were produced by aerosol techniques and size classified; nanocrystal size can be controlled in the size range of 2-50 nm with a size variation of less than 10%. Using a conducting tip, the charge was injected directly into the nanocrystals, and the subsequent dissipation of the charge was monitored. Estimates of the injected charge can be made by comparison of the data with an intermittent contact mode model of the AFM response to the electrostatic force produced by the stored charge
Propagation of optical excitations by dipolar interactions in metal nanoparticle chains
Dispersion relations for dipolar modes propagating along a chain of metal
nanoparticles are calculated by solving the full Maxwell equations, including
radiation damping. The nanoparticles are treated as point dipoles, which means
the results are valid only for a/d <= 1/3, where a is the particle radius and d
the spacing. The discrete modes for a finite chain are first calculated, then
these are mapped onto the dispersion relations appropriate for the infinite
chain. Computed results are given for a chain of 50-nm diameter Ag spheres
spaced by 75 nm. We find large deviations from previous quasistatic results:
Transverse modes interact strongly with the light line. Longitudinal modes
develop a bandwidth more than twice as large, resulting in a group velocity
that is more than doubled. All modes for which k_mode <= w/c show strongly
enhanced decay due to radiation damping.Comment: 26 pages, 7 figures, 2 tables. to appear in Phys. Rev.
Tunable vector beam decoder by inverse design for high-dimensional quantum key distribution with 3D polarized spatial modes
Spatial modes of light have become highly attractive to increase the
dimension and, thereby, security and information capacity in quantum key
distribution (QKD). So far, only transverse electric field components have been
considered, while longitudinal polarization components have remained neglected.
Here, we present an approach to include all three spatial dimensions of
electric field oscillation in QKD by implementing our tunable, on-a-chip vector
beam decoder (VBD). This inversely designed device pioneers the "preparation"
and "measurement" of three-dimensionally polarized mutually unbiased basis
states for high-dimensional (HD) QKD and paves the way for the integration of
HD QKD with spatial modes in multifunctional on-a-chip photonics platforms.Comment: 10 pages, 3 figure
All-optical active plasmonic devices with memory and power switching functionalities based on epsilon-near-zero nonlinear metamaterials
All-optical active plasmonic devices are of fundamental importance for
designing efficient nanophotonic circuits. We theoretically propose and
numerically investigate an active plasmonic device made up of a nonlinear
epsilon-near-zero metamaterial slab of thickness smaller than 100 nanometers
lying on a linear epsilon-near-zero metamaterial substrate. We predict that, in
free-space coupling configuration, the device, operating at low-intensity,
would display plasmon mediated hysteresis behavior since the phase difference
between the reflected and the incident optical waves turns out to be
multi-valued and dependent on the history of the excitation process. Such an
hysteresis behavior would allow to regard the proposed device as a compact
memory unit whose state is accessible by measuring either the mentioned phase
difference or the power, which is multi-valued as well, carried by the
nonlinear plasmon wave. Since multiple plasmon powers comprise both positive
and negative values, the device would also operate as a switch of the plasmon
power direction at each jump along an hysteresis loop.Comment: 9 pages, 4 figure
Simultaneous Surface Plasmon Resonance and X-ray Absorption Spectroscopy
We present here an experimental set-up to perform simultaneously measurements
of surface plasmon resonance (SPR) and X-ray absorption spectroscopy (XAS) in a
synchrotron beamline. The system allows measuring in situ and in real time the
effect of X-ray irradiation on the SPR curves to explore the interaction of
X-rays with matter. It is also possible to record XAS spectra while exciting
SPR in order to detect the changes in the electronic configuration of thin
films induced by the excitation of surface plasmons. Combined experiments
recording simultaneously SPR and XAS curves while scanning different parameters
can be carried out. The relative variations in the SPR and XAS spectra that can
be detected with this set-up ranges from 10-3 to 10-5, depending on the
particular experiment
Spatio-temporal dynamics and plastic flow of vortices in superconductors with periodic arrays of pinning sites
We present simulations of flux-gradient-driven superconducting rigid vortices
interacting with square and triangular arrays of columnar pinning sites in an
increasing external magnetic field. These simulations allow us to
quantitatively relate spatio-temporal microscopic information of the vortex
lattice with typically measured macroscopic quantities, such as the
magnetization . The flux lattice does not become completely commensurate
with the pinning sites throughout the sample at the magnetization matching
peaks, but forms a commensurate lattice in a region close to the edge of the
sample. Matching fields related to unstable vortex configurations do not
produce peaks in . We observe a variety of evolving complex flux
profiles, including flat terraces or plateaus separated by winding
current-carrying strings and, near the peaks in , plateaus only in
certain regions, which move through the sample as the field increases
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