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Kosmos
Astronomia Astrofizyka
Inne

Kultura
Sztuka dawna i współczesna, muzea i kolekcje

Metoda
Metodologia nauk, Matematyka, Filozofia, Miary i wagi, Pomiary

Materia
Substancje, reakcje, energia
Fizyka, chemia i inżynieria materiałowa

Człowiek
Antropologia kulturowa Socjologia Psychologia Zdrowie i medycyna

Wizje
Przewidywania Kosmologia Religie Ideologia Polityka

Ziemia
Geologia, geofizyka, geochemia, środowisko przyrodnicze

Życie
Biologia, biologia molekularna i genetyka

Cyberprzestrzeń
Technologia cyberprzestrzeni, cyberkultura, media i komunikacja

Działalność
Wiadomości | Gospodarka, biznes, zarządzanie, ekonomia

Technologie
Budownictwo, energetyka, transport, wytwarzanie, technologie informacyjne

# Kolekcje IOP - SELECT

Institute of Physics

## Nanoparticles for fingermark detection: an insight into the reaction mechanism

This publication presents one of the first uses of silicon oxide nanoparticles to detect
fingermarks. The study is not confined to showing successful detection of fingermarks, but is
focused on understanding the mechanisms involved in the fingermark detection process. To gain such
an understanding, various chemical groups are grafted onto the nanoparticle surface, and parameters
such as the pH of the solutions or zeta potential are varied to study their influence on the
detection. An electrostatic interaction has been the generally accepted hypothesis of interaction
between nanoparticles and fingermarks, but the results of this research challenge that hypothesis,
showing that the interaction is chemically driven. Carboxyl groups grafted onto the nanoparticle
surfaces react with amine groups of the fingermark secretion. This formation of amide linkage
between carboxyl and amine groups has further been favoured by catalyzing the reaction with a
compound of diimide type. The researc...

2014/10/02 - 20:12

## Particle image velocimetry correlation signal-to-noise ratio metrics and measurement uncertainty quantification

In particle image velocimetry (PIV) the measurement signal is contained in the recorded intensity of
the particle image pattern superimposed on a variety of noise sources. The signal-to-noise-ratio
(SNR) strength governs the resulting PIV cross correlation and ultimately the accuracy and
uncertainty of the resulting PIV measurement. Hence we posit that correlation SNR metrics calculated
from the correlation plane can be used to quantify the quality of the correlation and the resulting
uncertainty of an individual measurement. In this paper we extend the original work by Charonko and
Vlachos and present a framework for evaluating the correlation SNR using a set of different metrics,
which in turn are used to develop models for uncertainty estimation. Several corrections have been
applied in this work. The SNR metrics and corresponding models presented herein are expanded to be
applicable to both standard and filtered correlations by applying a subtraction of the minimum
correlatio...

2014/09/24 - 16:08

## Vertical cracks characterization using lock-in thermography: I infinite cracks

Early detection of cracks is a challenging task to prevent failures in working structures. In the
last decades the ‘flying spot’ method, based on heating the sample with a moving laser spot and
detecting the surface temperature with an infrared detector, has been developed to detect cracks in
a fast manner. The aim of this work is to measure the width of an infinite vertical crack using
lock-in thermography. An analytical solution for the surface temperature of a sample containing such
a crack when the surface is illuminated by a modulated laser beam focused at a fixed spot close to
the crack is obtained. Measurements on samples containing calibrated cracks have been performed
using an infrared camera. A least square fit of the amplitude and phase of the surface temperature
is used to retrieve the thickness of the crack. A very good agreement between the nominal and
retrieved thicknesses of fissure is found, even for widths down to 1  µ m, confirming the validity
of the mode...

2014/09/24 - 16:08

## Low volume ultrasonic resonator for liquid characterization under continuous flow conditions

A new ultrasonic resonator called MICRUS for measuring and characterizing liquid samples in
continuous flow is presented. High accuracy and thermal stability are obtained by handling small
liquid volumes passing through a heat exchanger before reaching the ultrasonic measurement chamber.
The core measuring element consists of a resonant quartz flow-cell with LiNbO 3 piezoelectric discs
attached face-to-face. The resonator is operated using pulsed excitation to provide rapid
measurements. The software is implemented in LabView, giving a friendly and fully-automated
interface well-suited for process monitoring. Different measurements for checking instrument
performance (temperature stability, solute detection, measurement repeatability) are performed and
a ±0.024 m s −1 uncertainty is obtained. Application examples requiring liquid measurement under
continuous flow conditions are also presented. When monitoring processes taking place in containers
and conduits w...

2014/09/24 - 16:08

## Vertical cracks characterization using lock-in thermography: II finite cracks

The aim of this work is to characterize vertical cracks of finite size and arbitrary shape using
optically excited lock-in thermography. In the first place, we have solved the direct problem, which
consists of calculating the surface temperature distribution when the shape, size and width of the
vertical crack are known. To do this we have developed a new method based on discontinuous finite
elements, which allows one to deal even with very narrow cracks, for which classical finite element
methods fail. The surface temperature of steel samples containing semi-infinite cracks and
illuminated with a laser beam focused close to the crack has been measured using a lock-in
thermography setup. A least square fit of the amplitude and phase of the surface temperature is used
to retrieve the width and depth of the semi-infinite crack. A very good agreement between the
nominal and retrieved values of both parameters is found, confirming the validity of the model.

2014/09/24 - 16:08

## Dual-colored graphene quantum dots-labeled nanoprobes/graphene oxide: functional carbon materials for respective and simultaneous detection of DNA and thrombin

Convenient and simultaneous detection of multiple biomarkers such as DNA and proteins with
biocompatible materials and good analytical performance still remains a challenge. Herein, we report
the respective and simultaneous detection of DNA and bovine α -thrombin (thrombin) entirely based on
biocompatible carbon materials through a specially designed fluorescence on-off-on process. Colorful
fluorescence, high emission efficiency, good photostability and excellent compatibility enables
graphene quantum dots (GQDs) as the best choice for fluorophores in bioprobes, and thus two-colored
GQDs as labeling fluorophores were chemically bonded with specific oligonucleotide sequence and
aptamer to prepare two probes targeting the DNA and thrombin, respectively. Each probe can be
assembled on the graphene oxide (GO) platform spontaneously by π – π stacking and electrostatic
attraction; as a result, fast electron transfer in the assembly efficiently quenches the
fluorescenc...

2014/09/24 - 16:08

## A first principles scanning tunneling potentiometry study of an opaque graphene grain boundary in the ballistic transport regime

We report on a theoretical interpretation of scanning tunneling potentiometry (STP), formulated
within the Keldysh non-equilibrium Greenʼs function description of quantum transport. By treating
the probe tip as an electron point source/sink, it is shown that this approach provides an intuitive
bridge between existing theoretical interpretations of scanning tunneling microscopy and STP. We
illustrate this through ballistic transport simulations of the potential drop across an opaque
graphene grain boundary, where atomistic features are predicted that might be imaged through high
resolution STP measurements. The relationship between the electrochemical potential profile measured
and the electrostatic potential drop across such a nanoscale defect is also explored in this model
system.

2014/09/24 - 16:08

## A shearing-based method for the simultaneous calibration of angle measuring devices

In this paper, we present a novel adaptation of the shearing method to the simultaneous calibration
of angle measuring devices which is based on multiple comparisons of their angle readings in
different relative angular orientations. Without recourse to an external standard, the errors of the
two devices can be recovered, up to their linear components, from a set of three comparisons. We
demonstrate the method by the use of an autocollimator and an angle encoder. It proved to be ideally
suited for the calibration of interpolation errors of the devices at small angular scales which are
difficult to characterize with other methods. In the case that the linear components of the errors
are needed, too, only two angle differences, which correspond to the changes in the relative angular
orientations of the devices, need to be traced back to an external standard. A comprehensive
overview, both theoretical and experimental, of the capabilities and limitations of the method is
presented, ...

2014/09/17 - 01:36

## Resonance parameter estimation from spectral data: Cramér–Rao lower bound and stable algorithms with application to liquid sensors

A recently introduced method for robust determination of the parameters of strongly damped
resonances is evaluated in terms of achievable accuracy. The method extracts and analyzes the locus
of the resonant subsystem of noisy recorded complex spectra, such that the interfering influences of
many environmental factors are eliminated. Estimator performance is compared to the absolute lower
limit determining the Cramér–Rao lower bound (CRLB) for the variance of the estimated parameters. A
generic model that is suitable for representation of a large class of sensors is used and analyzed.
It is shown that the proposed robust method converges to the CRLB for low measurement noise.

2014/09/17 - 01:36

## The effect of the inversion channel at the AlN/Si interface on the vertical breakdown characteristics of GaN-based devices

GaN-on-Si transistors attract increasing interest for power applications. However, the breakdown
behavior of such devices remains below theoretical expectations, for which the Si substrate is
typically made responsible. In this work, the effect of the thickness of an aluminum nitride buffer
layer on the vertical breakdown voltage, measured relative to a grounded silicon substrate, has been
investigated. A voltage-polarity-dependent breakdown mechanism has been observed. It has been found
that the breakdown in the positive bias voltage regime is initiated by carrier injection, for which
the carriers originate from an inversion channel formed between the epitaxial layers and the
p-silicon substrate. TCAD simulations have confirmed the proposed explanations, and suggest that
appropriate modification of the electronic structure at the AlN/silicon interface could
significantly improve the vertical breakdown voltage.

2014/09/13 - 15:06

## The impact of structural relaxation on spin polarization and magnetization reversal of individual nano structures studied by spin-polarized scanning tunneling microscopy

The application of low temperature spin-polarized scanning tunneling microscopy and spectroscopy in
magnetic fields for the quantitative characterization of spin polarization, magnetization reversal
and magnetic anisotropy of individual nano structures is reviewed. We find that structural
relaxation, spin polarization and magnetic anisotropy vary on the nm scale near the border of a
bilayer Co island on Cu(1 1 1). This relaxation is lifted by perimetric decoration with Fe. We
discuss the role of spatial variations of the spin-dependent electronic properties within and at the
edge of a single nano structure for its magnetic properties.

2014/09/13 - 15:06

## Building blocks for studies of nanoscale magnetism: adsorbates on ultrathin insulating Cu 2 N

Scanning tunneling microscopy and spectroscopy were performed to study transition metal adatoms (Fe,
Co, Cu) and individual metal-dithiol complexes on insulating Cu 2 N islands. Adsorption of metal
adatoms on Cu 2 N is surprisingly complex and in the case of Fe, we find two distinct adsorption
states for each of two distinct adsorption sites. Connection of these metal adatoms to dithiol
molecules was pursued to model a single molecule junction, with the aim of understanding further
details about the nature of metal/molecule electrical contact. Pronounced changes in local density
of states, magnetic anisotropy and Kondo interactions were observed for Co adatoms connected to
dithiol molecules. These results illustrate some of the challenges and opportunities for STM studies
of nanoscale magnetism in complex systems.

2014/09/13 - 15:06

## Interaction of Mn with GaAs and InSb: incorporation, surface reconstruction and nano-cluster formation

The deposition of Mn on to reconstructed InSb and GaAs surfaces, without coincident As or Sb flux,
has been studied by reflection high energy electron diffraction, atomic force microscopy and
scanning tunnelling microscopy. On both Ga- and As-terminated GaAs(0 0 1), (2 × n) Mn-induced
reconstruction domains arise with n = 2 for the most well ordered reconstructions. On the
Ga-terminated (4 × 6), the Mn-induced (2 × 2) persists up to around 0.5 ML Mn followed by Mn
nano-cluster formation. For deposition on initially β 2(2 × 4)-reconstructed GaAs(0 0 1), the
characteristic trench structure of the reconstruction is partially preserved even beyond 1 monolayer
Mn coverage. On both the β 2(2 × 4) and c(4 × 4) surfaces, MnAs-like nano-clusters form alongside
the reconstruction changes. In contrast, there are no new Mn-induced surface reconstructions on
InSb. Instead, the Sb-terminated surfaces of InSb (0 0 1), (1 1 1)A and (1 1 1)B revert to
reconstructions characteri...

2014/09/13 - 15:06

## On the equivalence of Ising models on ‘small-world’ networks and LDPC codes on channels with memory

We demonstrate the equivalence between thermodynamic observables of Ising spin-glass models on
small-world lattices and the decoding properties of error-correcting low-density parity-check codes
on channels with memory. In particular, the self-consistent equations for the effective field
distributions in the spin-glass model within the replica symmetric ansatz are equivalent to the
density evolution equations forr Gilbert–Elliott channels. This relationship allows us to present a
belief-propagation decoding algorithm for finite-state Markov channels and to compute its
performance at infinite block lengths from the density evolution equations. We show that loss of
reliable communication corresponds to a first order phase transition from a ferromagnetic phase to a
paramagnetic phase in the spin glass model. The critical noise levels derived for Gilbert–Elliott
channels are in very good agreement with existing results in coding theory. Furthermore, we use our
analysis to derive crit...

2014/09/13 - 15:06

## Boundary dynamics driven entanglement

We will show how to generate entangled states out of unentangled states on a bipartite system by
means of dynamical boundary conditions. The auxiliary system is defined by a symmetric but not
self-adjoint Hamiltonian, and we will also study the space of self-adjoint extensions of the
bipartite system. We will show that only a small set of these extensions leads to separable
dynamics, and we will characterize these extensions. Various simple examples illustrating this
phenomenon are discussed; in particular, we will analyze the hybrid system consisting of a planar
quantum rotor and a spin system under a wide class of boundary conditions.

2014/09/13 - 15:06

## Excitation of random intense single-cycle light-pulse chains in optical fiber

Excitation of intense periodic single-cycle light pulses in a stochastic background arising from
continuous wave stimulated Brillouin scattering (SBS) in a long optical fiber with weak optical
feedback is found experimentally and modeled theoretically. Such intense light-pulse chains occur
randomly and the optical feedback is a requirement for their excitation. The probability of these
forms, among the large number of experimental output signals with identifiable waveforms, appearing
is only about 3%, with the remainder exhibiting regular SBS characteristics. It is also found that
pulses with low period numbers appear more frequently and the probability distribution for their
occurrence in terms of the pulse power is roughly L-shaped, like that for rogue waves. The results
from a three-wave-coupling model for SBS including feedback phase control agree well qualitatively
with the observed phenomena.

2014/09/12 - 12:39

## Polarization angle affects energy of plasmonic features in Fano resonant regular lattices

Plasmonic nanoparticles in ordered lattices exhibit spectral features supported by Fano resonant
coupling between dipole and/or quadrupole oscillations and constructively interfering diffracted
modes. This work showed that the angle at which incident resonant irradiation was polarized relative
to the axes of a rectangular 655 × 649 nm 2 lattice of 264 nm diameter gold nanospheres predictably
modulated the energy of plasmonic spectral features. Measured peak wavelengths varied sinusoidally
as polarization angle was rotated 360°. Quadrupole and dipole lattice resonance oscillations were
phase shifted by 90°, consistent with theory. Experimental wavelengths were within 12 nanometers
(1.8%) of wavelengths simulated for the lattice using a coupled dipole/quadrupole approximation.

2014/09/09 - 15:41

## Transparent conducting oxide nanotubes

Thin film or porous membranes made of hollow, transparent, conducting oxide (TCO) nanotubes, with
high chemical stability, functionalized surfaces and large surface areas, can provide an excellent
platform for a wide variety of nanostructured photovoltaic, photodetector, photoelectrochemical and
photocatalytic devices. While large-bandgap oxide semiconductors offer transparency for incident
light (below their nominal bandgap), their low carrier concentration and poor conductivity makes
them unsuitable for charge conduction. Moreover, materials with high conductivity have nominally low
bandgaps and hence poor light transmittance. Here, we demonstrate thin films and membranes made from
TiO 2 nanotubes heavily-doped with shallow Niobium (Nb) donors (up to 10%, without phase
segregation), using a modified electrochemical anodization process, to fabricate transparent
conducting hollow nanotubes. Temperature dependent current–voltage characteristics revealed that TiO
2

2014/09/02 - 21:32

## The Koslowski–Sahlmann representation: quantum configuration space

The Koslowski–Sahlmann (KS) representation is a generalization of the representation underlying the
discrete spatial geometry of loop quantum gravity (LQG), to accommodate states labelled by smooth
spatial geometries. As shown recently, the KS representation supports, in addition to the action of
the holonomy and flux operators, the action of operators which are the quantum counterparts of
certain connection dependent functions known as ‘background exponentials’. Here we show that the KS
representation displays the following properties which are the exact counterparts of LQG ones: (i)
the abelian * algebra of ##IMG##
[http://ej.iop.org/images/0264-9381/31/17/175009/cqg499133ieqn1.gif] {$SU(2)$} holonomies and ‘
##IMG## [http://ej.iop.org/images/0264-9381/31/17/175009/cqg499133ieqn2.gif] {$U(1)$} ’ background
exponentials can be completed to a C * algebra, (ii) the space of semianalytic ##IMG## {$SU(2)$}

2014/09/02 - 21:32

## GSE statistics without spin

Energy level statistics following the Gaussian Symplectic Ensemble (GSE) of Random Matrix Theory
have been predicted theoretically and observed numerically in numerous quantum chaotic systems.
However, in all these systems there has been one unifying feature: the combination of half-integer
spin and time-reversal invariance. Here we provide an alternative mechanism for obtaining GSE
statistics that is derived from geometric symmetries of a quantum system which alleviates the need
for spin. As an example, we construct a quantum graph with a discrete symmetry given by the
quaternion group Q 8 and observe GSE statistics within one of its subspectra. We then show how to
isolate this subspectrum and construct a quantum graph with a scalar valued wave function and a pure
GSE spectrum.

2014/08/30 - 13:10

## Interaction corrections to the minimal conductivity of graphene via dimensional regularization

We compute the two-loop interaction correction to the minimal conductivity of disorder-free
intrinsic graphene with the help of dimensional regularization. The calculation is done in two
different ways: via density-density and via current-current correlation functions. Upon properly
renormalizing the perturbation theory, in both cases, we find that ##IMG##
[http://ej.iop.org/images/0295-5075/107/5/57001/epl16495ieqn1.gif] {$\sigma = \sigma_0\,( 1 + \alpha\,(19-6\pi)/12) \approx \sigma_0 \,(1 + 0.01\, \alpha)$} , where ##IMG##
[http://ej.iop.org/images/0295-5075/107/5/57001/epl16495ieqn2.gif] {$\alpha = e^2 / (4 \pi \hbar v)$} is the renormalized fine structure constant and ##IMG##
[http://ej.iop.org/images/0295-5075/107/5/57001/epl16495ieqn3.gif] {$\sigma_0 = e^2 / (4 \hbar)$} .
Our results are consistent with experimental uncertainties and resolve a theoretical dispute.

2014/08/30 - 13:10

## Capillary rise of yield-stress fluids

In this letter the capillary rise of yield-stress fluids is investigated experimentally. Contrary to
the case of simple fluids, the final height reached by yield-stress fluids weakly depends on the gap
and is strongly affected by the yield stress and the hydrodynamic boundary conditions. Such
dependences suggest that the capillary rise of yield-stress fluids results from a dynamical arrest
rather than from a thermodynamic equilibrium. To rationalize these results, we propose and validate
an extension of Jurin's law to such complex systems. Finally we show that measuring the final height
allows for the determination of both the surface tension and the yield stress.

2014/08/30 - 13:10

## Tensile strength of carbyne chains in varied chemical environments and structural lengths

Carbyne and carbyne-based low-dimensional structures are promising for several applications
including ultra-compact circuits and purification devices. Designing any applied carbyne-based
structure requires a fundamental understanding of the mechanical strength of carbyne chains with
different lengths at different temperatures and operating chemical environment. Here we use
molecular dynamics simulations to investigate the strength of carbyne chains with different lengths
at different temperatures. A theoretical framework based on statistical mechanics and molecular
dynamics results is presented, proving a fast and insightful method for predicting the rupture force
and its physical mechanism. The effect of water molecules’ interaction is also studied on the
mechanical properties and it is shown that both the tensile strength and rupture strain are improved
by the water interaction. The results of this work can be used for designing and analyzing the
robustness and reliability of v...

2014/08/27 - 21:23

## A high-bandwidth spintronic position sensor

Position sensing with resolution down to the scale of a single atom is of key importance in
nanoscale science and engineering. However, only optical-sensing methods are currently capable of
non-contact sensing at such resolution over a high bandwidth. Here, we report a new non-contact,
non-optical position-sensing concept based on detecting changes in a high-gradient magnetic field of
a microscale magnetic dipole by means of spintronic sensors. Experimental measurements show a
sensitivity of up to 40 ##IMG##
[http://ej.iop.org/images/0957-4484/25/37/375501/nano496471ieqn1.gif] {$\Omega$} / μ m, a linear
range greater than 10 μ m and a noise floor of 0.5 pm/ ##IMG##
[http://ej.iop.org/images/0957-4484/25/37/375501/nano496471ieqn2.gif] {$\sqrt{\;{\rm Hz}}$} . Also
shown is the use of the sensor for position measurements for closed-loop control of a high-speed
atomic force microscope with a frame rate of more than 1 frame/s.

2014/08/27 - 21:23

## Scanning magnetic tunnel junction microscope for high-resolution imaging of remanent magnetization fields

Scanning magnetic microscopy is a new methodology for mapping magnetic fields with high spatial
resolution and field sensitivity. An important goal has been to develop high-performance instruments
that do not require cryogenic technology due to its high cost, complexity, and limitation on
sensor-to-sample distance. Here we report the development of a low-cost scanning magnetic microscope
based on commercial room-temperature magnetic tunnel junction (MTJ) sensors that typically achieves
spatial resolution better than 7  µ m. By comparing different bias and detection schemes, optimal
performance was obtained when biasing the MTJ sensor with a modulated current at 1.0 kHz in a
Wheatstone bridge configuration while using a lock-in amplifier in conjunction with a low-noise
custom-made preamplifier. A precision horizontal ( x – y ) scanning stage comprising two coupled
nanopositioners controls the position of the sample and a linear actuator adjusts the
sensor-to-sample ...

2014/08/21 - 23:45

## Enhancing the brightness of Si nanocrystal light-emitting devices with electro-excited surface plasmons

The use of electro-excited surface plasmons (SPs) in Ag nanoparticles (Ag-NPs) is shown to enhance
the brightness of Si nanocrystal light-emitting devices (Si-NC LEDs). The Ag-NPs are prepared on the
Si-NC thin film by ultrasonic irradiation and postannealing treatments. Electro-excited SPs on
Ag-NPs are found, which are induced by electron impact on Ag-NPs and the front electrode Al layer
during the charge injection process of LED. The electro-excited SPs enhance the electroluminescence
of Si-NC, or LED brightness, via the SP field coupling to the exciton dipole moment of Si-NC. A
maximal 5.2-fold brightness enhancement of Si-NC LED is achieved at the postannealing temperature of
200 °C. Remnant far-field radiations arising from electro-excited SPs are detected, which further
supports the existence of such SPs.

2014/08/14 - 18:00

## Oxidation of nanopores in a silicon membrane: self-limiting formation of sub-10 nm circular openings

We describe a simple but reliable approach to shrink silicon nanopores with nanometer precision for
potential high throughput biomolecular sensing and parallel DNA sequencing. Here, nanopore arrays on
silicon membranes were fabricated by a self-limiting shrinkage of inverted pyramidal pores using dry
thermal oxidation at 850 °C. The shrinkage rate of the pores with various initial sizes saturated
after 4 h of oxidation. In the saturation regime, the shrinkage rate iswithin ± 2 nm h −1 . Oxidized
pores with an average diameter of 32 nm were obtained with perfect circular shape. By careful design
of the initial pore size, nanopores with diameters as small as 8 nm have been observed. Statistics
of the pore width show that the shrinkage process did not broaden the pore size distribution; in
most cases the distribution even decreased slightly. The progression of the oxidation and the
deformation of the oxide around the pores were characterized by focused ion beam and electr...

2014/08/14 - 18:00

## Separation of the piezotronic and piezoresistive effects in a zinc oxide nanowire

The strain-induced band structure change in a semiconductor can change its resistivity, known as the
piezoresistive effect. If the semiconductor is also a piezoelectric material, strain-induced
polarization charge can control the current transport at the metal-semiconductor contact, which is
called a ‘piezotronic effect’. Piezotronic effect is intertwined with piezoresistive effect in the
study of present piezotronic nanowire devices. Decoupling those effects will facilitate the
fundamental study on the piezotronic devices and simplify the data analysis in real applications.
Here, we report a general method to separate the piezotronic and piezoresistive effects in the same
nanowire, based on modified four-point measurements. Current transport characteristics of each
contact was extracted and showed different responses to the strain. The piezoresistive effect was
measured in zinc oxide nanowires for the first time, and the result confirmed the dominant role of
piezotronic effect i...

2014/08/08 - 05:51

## Effects of high temperature annealing on defects and luminescence properties in H implanted ZnO

The evolution of luminescence properties and voids formation with respect to annealing temperature
in H implanted ZnO was investigated by depth-resolved cathodoluminescence spectroscopy (DRCLS),
transmission electron microscopy and secondary ion mass spectrometry (SIMS). The annealing
temperature is found to induce noticeable changes to the shape, size and empty volume density of the
cavities. DRCLS results also reveal that the green emission is influenced by different annealing
temperatures. In particular, the 600 °C anneal produces a strong quenching of the green emission in
the implanted region, while after the 800 °C anneal a significant enhancement near the surface is
observed. The annealing at 600 °C also results in an uncommon violet emission at ∼3.1 eV that is not
observed after a higher annealing temperature. A clear correlation between the violet emission,
vacancies and Li is revealed from comparison between the DRCLS intensities and SIMS data.

2014/08/05 - 19:03

## Magnetic effect on the interfacial energy of the Ni(1 1 1)/Cr(1 1 0) interface

The work of separation and interfacial energy of the Ni(1 1 1)/Cr(1 1 0) interface are calculated
via first-principles methods. Both coherent and semicoherent interfaces are considered. We find that
magnetism has a significant effect on the interfacial energy, i.e. removing magnetism decreases the
interfacial energy of the semicoherent interface by around 50% . Electronic, magnetic and atomic
structures at the interface are discussed. An averaging scheme is used to estimate the work of
separation and interfacial energy of semicoherent interfaces based on the results of coherent
interfaces. The limitations of the scheme are discussed.

2014/07/31 - 10:31

## Electrical and microstructural properties of thermally annealed Ni/Au and Ni/Pt/Au Schottky contacts on AlGaN/GaN heterostructures

High work-function metals such as Ni, Pt, and Au in the form of multilayer structures, Ni/Au and
Ni/Pt/Au, have been investigated as Schottky metallizations on AlGaN/GaN heterostructures under
thermal annealing. As-deposited Ni/Pt/Au had slightly higher Schottky barrier height than its Ni/Au
counterpart. Schottky barrier heights for Ni/Au diodes on AlGaN/GaN increased by about 20% from 1.02
eV for as-deposited to 1.21 eV after annealing at 500 °C for 2 min. Similar trends were observed for
Ni/Pt/Au Schottky diodes. Thermal stability study for these devices showed that the interposition of
Pt in Ni/Au systems improved the characteristics of the Schottky diodes after short-term anneal but
cause significant degradation after long-term anneal at 500 °C. Ni/Au Schottky contacts exhibited
excellent leakage response under thermal annealing for long periods. Microstructural studies were
carried out on Ni/Pt/Au and Ni/Au Schottky contacts to elucidate the role of the Pt interlayer in
the ...

2014/07/31 - 10:31

## Focused ion beam lithography for fabrication of suspended nanostructures on highly corrugated surfaces

We propose a nanofabrication method that allows for patterning on extremely corrugated surfaces with
micrometer-size features. The technique employs focused ion beam nanopatterning of ion-sensitive
inorganic resists formed by atomic layer deposition at low temperature. The nanoscale resolution on
corrugated surfaces is ensured by inherently large depth of focus of a focused ion beam system and
very uniform resist coating. The utilized TiO 2 and Al 2 O 3 resists show high selectivity in deep
reactive ion etching and enable the release of suspended nanostructures by dry etching. We
demonstrate the great flexibility of the process by fabricating suspended nanostructures on flat
surfaces, inclined walls, and on the bottom of deep grooves.

2014/07/31 - 10:31

## Confinement and controlling the effective compressive stiffness of carbyne

Carbyne is a one-dimensional chain of carbon atoms, consisting of repeating sp -hybridized groups,
thereby representing a minimalist molecular rod or chain. While exhibiting exemplary mechanical
properties in tension (a 1D modulus on the order of 313 nN and a strength on the order of 11 nN),
its use as a structural component at the molecular scale is limited due to its relative weakness in
compression and the immediate onset of buckling under load. To circumvent this effect, here, we
probe the effect of confinement to enhance the mechanical behavior of carbyne chains in compression.
Through full atomistic molecular dynamics, we characterize the mechanical properties of a free
(unconfined chain) and explore the effect of confinement radius ( R ), free chain length ( L ) and
temperature ( T ) on the effective compressive stiffness of carbyne chains and demonstrate that the
stiffness can be tuned over an order of magnitude (from approximately 0.54 kcal mol −...

2014/07/31 - 10:31

## Terahertz science and technology of carbon nanomaterials

The diverse applications of terahertz (THz) radiation and its importance to fundamental science
makes finding ways to generate, manipulate and detect THz radiation one of the key areas of modern
applied physics. One approach is to utilize carbon nanomaterials, in particular, single-wall carbon
nanotubes and graphene. Their novel optical and electronic properties offer much promise to the
field of THz science and technology. This article describes the past, current, and future of THz
science and technology of carbon nanotubes and graphene. We will review fundamental studies such as
THz dynamic conductivity, THz nonlinearities and ultrafast carrier dynamics as well as THz
applications such as THz sources, detectors, modulators, antennas and polarizers.

2014/07/31 - 10:31

## Solitons with a nested structure over finite fields

We propose a solitonic dynamical system over finite fields that may be regarded as an analogue of
the box–ball systems. The one-soliton solutions of the system, which have nested structures similar
to fractals, are also proved. The solitonic system in this paper is described by polynomials, which
seems to be novel. Furthermore, in spite of such complex internal structures, numerical simulations
exhibit stable propagations before and after collisions among multiple solitons, preserving their
patterns.

2014/07/31 - 10:31

## Magnetotransport properties in perpendicularly magnetized tunnel junctions using an ultrathin Fe electrode

The tunnel magnetoresistance (TMR) effect was investigated in perpendicularly magnetized magnetic
tunnel junctions (p-MTJs) consisting of a stacked layer structure of ultrathin Fe (0.7)/MgO
(1.8)/CoFeB (1.2–1.4) (in nm). A relatively large TMR ratio of 95% was obtained with an interface
perpendicular magnetic anisotropy energy density of 1.5 mJ m −2 at the Fe/MgO interface. Moreover,
we found that the p-MTJ exhibits spin-dependent resonant tunnelling characteristics in the bias
voltage dependence of differential conductance, corresponding to a quantum well confined in five
monolayers of the Fe(0 0 1) atomic plane. The results showed that the resonant tunnelling of Δ 1
symmetry electrons through the spin-dependent quantum well can be realized even in a p-MTJ structure
with strong perpendicular magnetic anisotropy.

2014/07/24 - 21:48

## A new metallic complex reaction etching for transition metals by a low-temperature neutral beam process

We investigated a new oxidation reaction at a low temperature (−30 °C) as a result of O 2 neutral
beam bombardment at a low activation energy (<0.025 eV), which can efficiently form a thin oxide
film of all transition metals, such as tantalum, ruthenium and platinum. Meanwhile, a new neutral
beam enhanced chemical etching for the neutral beam oxidized transition metals that uses a new
metallic complex reaction process and does not cause chemical or physical damage at low temperatures
was also proposed. As a result, a highly anisotropic etching profile without re-deposition on the
sidewall could be achieved with just the pure chemical reaction between ethanol and metallic oxide
at a low kinetic energy using the neutral beam process.

2014/07/24 - 21:48

## Correlations between atomic structure and giant magnetoresistance ratio in Co 2 (Fe,Mn)Si spin valves

We show that the magnetoresistance of Co 2 Fe x Mn 1− x Si-based spin valves, over 70% at low
temperature, is directly related to the structural ordering in the electrodes and at the
electrodes/spacer (Co 2 Fe x Mn 1− x Si/Ag) interfaces. Aberration-corrected atomic resolution Z
-contrast scanning transmission electron microscopy of device structures reveals that annealing at
350 °C and 500 °C creates partial B2/L2 1 and fully L2 1 ordering of electrodes, respectively.
Interface structural studies show that the Ag/Co 2 Fe x Mn 1− x Si interface is more ordered
compared to the Co 2 Fe x Mn 1− x Si/Ag interface. The release of interface strain is mediated by
misfit dislocations that localize the strain around the dislocation cores, and the effect of this
strain is assessed by first principles electr...

2014/07/24 - 21:48

## Universal properties of branching random walks in confined geometries

Characterizing the occupation statistics of random walks through confined geometries amounts to
assessing the distribution of the travelled length ℓ and the number of collisions n performed by the
stochastic process in a given region, for which remarkably simple Cauchy-like formulas were
established in the case of branching Pearson random walks with exponentially distributed jumps. In
this letter, we derive two key results: first, we show that such formulas strikingly carry over to
the much broader class of branching processes with arbitrary jumps, and have thus a universal
character; second, we obtain a stronger version of these formulas relating the travelled length
density and the collision density at any point of the phase space. Our results are key to such
technological issues as the analysis of radiation flow for nuclear reactor design and medical
diagnosis and apply more broadly to physical and biological systems with diffusion, reproduction and
death.

2014/07/24 - 21:48

## Luminance meter for photopic and scotopic measurements in the mesopic range

This paper presents a design and realization of a dual-channel luminance meter for simultaneous
measurement of luminance with photopic and scotopic weightings. Such measurements are useful in
mesopic conditions, i.e. when the luminance is in the range of 0.005–5 cd m −2 . The instrument is a
spot luminance meter with two spectrally weighted channels. The collected light is detected with
silicon detectors and a computer-controlled dual-channel switched-integration amplifier. The
instrument is characterized for relative spectral responsivity against a calibrated
spectroradiometer using a radiance source based on an integrating sphere with input from a
monochromator. An absolute luminance responsivity calibration is made against a sphere-based
luminance standard at a level close to the high end of the mesopic range. The standard uncertainty
in luminance responsivity calibration is 0.3% for the photopic channel and 0.6% for the scotopic