SEARCH · Searcharxiv

Results for “physics.app-ph”

Search indexed arXiv papers on artificial intelligence, large language models, computer vision and robotics. Read source abstracts and follow links to arXiv.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 559 records · Page 31Linked to original sources

arXiv2019

Spatial Control of Frost Formation on Surfaces with Millimetric Serrated Features

Numerous studies have focused on a low surface energy coating and a micro/nanoscale surface texture to design functional surfaces that delay frost formation and reduce ice adhesion. However, the scientific challenges for in developing icephobic surfaces have not been fully addressed because of degradation such as mechanical wearing. Inspired by the suppressed frost formation on concave regions of natural leaves, here we report findings on the frosting process on hydrophobic surfaces with various serrated structures. Dropwise condensation, the first stage of frosting, is enhanced on the peaks and suppressed in the valleys when the serrated surface is exposed to humid air, causing frosting to initiate from the peak. The condensed droplets in the valley are then evaporated due to the different equilibrium vapor pressure of ice and water, resulting in a non-frost band on both hydrophobic and superhydrophilic surfaces. The frost growth is systematically studied by employing various levels of ambient humidity, surface wettability, and surface geometry. Numerical simulations show the critical role of diffusion of water vapor in the formation of the discontinuous frost pattern.

physics.app-ph↗

arXiv2019

In-situ detecting cooperative-target's speed and rotation inertia using structured light

Laser remote sensing represents a powerful tool that enables the accurate measurement of the speed of moving targets. Crucially, most sensing techniques are 2-Dimensional and only enable direct determination of the speed along the line of sight. A disadvantage that is very often overcome using two-dimensional techniques that in many cases are hard to implement and expensive. Here we put forward a novel 3-Dimensional technique that enables the direct and simultaneous measurement of both, the speed and the spin rate of cooperative targets. This technique is based on the use of complex vector light beams, whose polarization and spatial degree of freedom are coupled in a non-separable way. We present experimental evidence of our technique by performing a laboratory proof-of-principle experiment.

physics.optics↗

arXiv2019

Coulomb blockade in Etched Single and Few Layer MoS2 Nanoribbons

Confinement in two-dimensional transition metal dichalcogenides is an attractive platform for trapping single charge and spins for quantum information processing. Here, we present low temperature electron transport through etched 50-70nm MoS2 nanoribbons showing current oscillations as a function of gate voltage. On further investigations current through the device forms diamond shaped domains as a function of source-drain and gate voltage. We associate these current oscillations and diamond shaped current domains with Coulomb blockade due to single electron tunneling through a quantum dot formed in the MoS2 nanoribbon. From the size of the Coulomb diamond, we estimate the quantum dot size as small as 10-35nm. We discuss the possible origins of quantum dot in our nanoribbon device and prospects to control or engineer the quantum dot in such etched MoS2 nanoribbons which can be a promising platform for spin-valley qubits in two-dimensional transition metal dichalcogenides.

cond-mat.mes-hall↗

arXiv2019

Ionic Electro active Polymer-Based Soft Actuators and Their Applications in Microfluidic Micropumps, Microvalves, and Micromixers: A Review

This paper provides a detailed review on applications of ionic electroactive polymer (i-EAP) soft actuators as active elements of microfluidic micropumps, microvalves, and micromixers. The related works that have so far been presented by various research groups in the field have been collected in this review, which in the presented comparative procedure here shows the progress of this field during the time. Microfluidic technology as a pioneer field in bioengineering needs to have some active components likes pumps, valves, and mixers to obtain efficient functionality. Most of the conventional microfluidic active components are challenging to assemble and control outside the laboratory since they need some special facilities, which is not cost-effective. This is while some of the main targets of the microfluidic devices are for the development of point of care (POC) diagnostic systems, home usability, ubiquitousness, and low-cost ability. To solve these problems, i-EAPs have shown promising features to be the proper candidates as active elements of the microfluidic devices. Ionic polymer-metal composites (IPMCs), Conducting polymer actuators (CPAs), and Ionic carbon nanotube-based actuators (i-CNTAs) are three main types of the i-EAPs. In this paper, the working principles, fabrication, and microfluidic-based applications of these three categories are described in details. To have a proper comparison between all the reported i-EAP based microfluidic devices, several important features, i.e., applied voltage/frequency, device materials, electrode material, membrane material, and the main measured index of each device, have been reviewed.

physics.app-ph↗

arXiv2019

Joule Heating-Induced Particle Manipulation on a Microfluidic Chip

We develop an electrokinetic technique that continuously manipulates colloidal particles to concentrate into patterned particulate groups in an energy efficient way, by exclusive harnessing of the intrinsic Joule heating effects. Our technique exploits the alternating current electrothermal flow phenomenon which is generated due to the interaction between non-uniform electric and thermal fields. Highly non-uniform electric field generates sharp temperature gradients by generating spatially-varying Joule heat that varies along radial direction from a concentrated point hotspot. Sharp temperature gradients induce local variation in electric properties which, in turn, generate strong electrothermal vortex. The imposed fluid flow brings the colloidal particles at the centre of the hotspot and enables particle aggregation. Further, manoeuvering structures of the Joule heating spots, different patterns of particle clustering may be formed in a low power budget, thus, opening up a new realm of on-chip particle manipulation process without necessitating highly focused laser beam which is much complicated and demands higher power budget. This technique can find its use in Lab-on-a-chip devices to manipulate particle groups, including biological cells.

physics.app-ph↗

arXiv2019

Dual Plasmonic Modes from In-Situ Silver Nanoparticle Formation via Diffusion at Silver / Dielectric Interfaces

Metal-dielectric interfaces of various geometries are fundamental photonic material platforms for surface plasmons. Surface plasmon polaritons and localized surface plasmons are two surface plasmon modes that are excited on planar and curved metal-dielectric interfaces, respectively. Herein, we demonstrate in-situ formation of silver nanoparticles by diffusion at a planar interface between sputter-deposited silver and nitride dielectrics. In one step, we synthesize a nanostructure that exhibits both localized surface plasmon resonances at silver nanoparticles and surface plasmon resonances at the planar interface. We develop an accurate optical model describing both surface plasmon modes by applying effective medium theories to experimental ToF-SIMS and XPS depth profiles. Our findings provide fundamental material insights into intrinsic metal-dielectric interfacial defects, along with a new in-situ nanoparticle synthesis method that seamlessly integrates with conventional fabrication of planar interfaces. These unique results open the prospect of promising photonic-plasmonic applications availing the coupling of both surface plasmon modes.

physics.optics↗

arXiv2019

Acoustic manipulation through zero-thickness perforated plane with strong-coupling effects

How to manipulate acoustic waves through thinner structures is always a challenging problem due to the linear proportional relationship between the structural thickness and the acoustic wavelength. Here, we show the possibility of breaking this relationship by the strong-coupling effects of the radiated waves on the zero-thickness two-dimensional perforated plane, rather than reducing the thickness of the three-dimensional structure by the resonance mechanism of the cavity structure. The strong-coupling effects can be achieved and regulated by the self and mutual radiation between acoustic waves from different holes in the zero-thickness plane. We experimentally demonstrate the effectiveness of our approach by implementing acoustic focusing and holography. Our work introduces a different perspective for manipulating acoustic waves and will enable the application of ultrathin acoustic devices.

physics.app-ph↗

arXiv2019

Lagrangian transport and chaotic advection in three-dimensional laminar flows

Transport and mixing of scalar quantities in fluid flows is ubiquitous in industry and Nature. Turbulent flows promote efficient transport and mixing by their inherent randomness. Laminar flows lack such a natural mixing mechanism and efficient transport is far more challenging. However, laminar flow is essential to many problems and insight into its transport characteristics of great importance. Laminar transport, arguably, is best described by the Lagrangian fluid motion (`advection') and the geometry, topology and coherence of fluid trajectories. Efficient laminar transport being equivalent to `chaotic advection' is a key finding of this approach. The Lagrangian framework enables systematic analysis and design of laminar flows. However, the gap between scientific insights into Lagrangian transport and technological applications is formidable primarily for two reasons. First, many studies concern two-dimensional (2D) flows yet the real world is three dimensional (3D). Second, Lagrangian transport is typically investigated for idealised flows yet practical relevance requires studies on realistic 3D flows. The present review aims to stimulate further development and utilisation of know-how on 3D Lagrangian transport and its dissemination to practice. To this end 3D practical flows are categorised into canonical problems. First, to expose the diversity of Lagrangian transport and create awareness of its broad relevance. Second, to enable knowledge transfer both within and between scientific disciplines. Third, to reconcile practical flows with fundamentals on Lagrangian transport and chaotic advection. This may be a first incentive to structurally integrate the `Lagrangian mindset' into the analysis and design of 3D practical flows.

physics.flu-dyn↗

arXiv2019

On-Chip Integrable Planar NbN NanoSQUID with Broad Temperature and Magnetic-Field Operation Range

Superconducting quantum interference devices (SQUIDs) are used for applications ranging from sensitive magnetometers to low-temperature electronics and quantum computation. We introduce a planar nano SQUID that was made with a single lithographic step out of NbN films as thin as 3 nm on a Si chip. The fabrication process of weak links that are 45 nm in width, and 165 nm in length, which were designed to account for overcoming current crowding are presented. Operation at a temperature range of 20 mK to 5 K as well as at 1 T parallel, and 10 mT perpendicular magnetic fields is demonstrated, while potential operation higher than 8 T has also been shown. The broad range of applicability of a single device as well as its scalability are promising for on-chip integrability that may open new technological possibilities, including in quantum and electro-optical circuiting.

physics.app-ph↗

arXiv2019

Experimental Demonstration of Staggered CAP Modulation for Low Bandwidth Red-Emitting Polymer-LED based Visible Light Communications

In this paper we experimentally demonstrate, for the first time, staggered carrier-less amplitude and phase (sCAP) modulation for visible light communication systems based on polymer light-emitting diodes emitting at ~639 nm. The key advantage offered by sCAP in comparison to conventional multiband CAP is its full use of the available spectrum. In this work, we compare sCAP, which utilises four orthogonal filters to generate the signal, with a conventional 4-band multi-CAP system and on-off keying (OOK). We transmit each modulation format with equal energy and present a record un-coded transmission speed of ~6 Mb/s. This represents gains of 25% and 65% over the achievable rate using 4-CAP and OOK, respectively.

cs.NI↗

arXiv2019

Gas-phase synthesis of carbon nanotube-graphene heterostructures

Graphene and carbon nanotubes (CNTs) share the same atomic structure of hexagonal carbon lattice. Yet, their synthesis differs in many aspects, including the shape and size of the catalyst. Here, we demonstrate a floating-catalyst chemical vapor deposition (FCCVD) technique for substrate-free, single-step growth of CNT-graphene heterostructures (CNT-G-H) using ethylene as a carbon source. The formation of CNT-G-H is directly evidenced by lattice-resolved (scanning) transmission electron microscopy (STEM) and electron diffraction experiments, corroborated by atomic force microscopy (AFM). Our experiments show the relative number density of graphene-nanoflakes can be tuned by optimizing the synthesis conditions. Since in the applied process the formation of the structures take place in gas-suspension, the as-synthesized CNT-G-H films can be deposited on any surface in ambient temperature with an arbitrary thickness. Moreover, this process of CNT-G-H synthesis with strong universality has also been realized in multiple systems of ethylene-based FCCVD with various catalysts and set-ups.

physics.app-ph↗

arXiv2019

GHz Dielectric Measurement of Powdery TiO

This study experimentally determines the dielectric properties of a powdery titanium (II) oxide (TiO) material within the microwave range (0.1-13.5 GHz). The properties were determined using a coaxial airline method using a TiO/paraffin mixture at several loading fractions. A permittivity of 60 for volume fraction below 30% and 100 for volume fraction above were measured.

physics.app-ph↗

arXiv2019

Multiplication and division of the orbital angular momentum of light with diffractive transformation optics

We present a method to efficiently multiply or divide the orbital angular momentum (OAM) of light beams using a sequence of two optical elements. The key-element is represented by an optical transformation mapping the azimuthal phase gradient of the input OAM beam onto a circular sector. By combining multiple circular-sector transformations into a single optical element, it is possible to perform the multiplication of the value of the input OAM state by splitting and mapping the phase onto complementary circular sectors. Conversely, by combining multiple inverse transformations, the division of the initial OAM value is achievable, by mapping distinct complementary circular sectors of the input beam into an equal number of circular phase gradients. The optical elements have been fabricated in the form of phase-only diffractive optics with high-resolution electron-beam lithography. Optical tests confirm the capability of the multiplier optics to perform integer multiplication of the input OAM, while the designed dividers are demonstrated to correctly split up the input beam into a complementary set of OAM beams. These elements can find applications for the multiplicative generation of higher-order OAM modes, optical information processing based on OAM-beams transmission, and optical routing/switching in telecom.

physics.optics↗

arXiv2019

Plasma Wakefield Accelerator Research 2019 - 2040: A community-driven UK roadmap compiled by the Plasma Wakefield Accelerator Steering Committee (PWASC)

The acceleration gradients generated in a laser- or beam-driven plasma wakefield accelerator are typically three orders of magnitude greater than those produced by a conventional accelerator, and hence plasma accelerators can open a route to a new generation of very compact machines. In addition, plasma-based accelerators can generate beams with unique properties, such as tens of kiloamp peak currents, attosecond bunch duration, ultrahigh brightness and intrinsic particle beam-laser pulse synchronization. In this roadmap we review the status of plasma accelerator research in the UK. We outline potential applications, describe the research and development required to enable those applications, and discuss synergies with related areas of research. We also set-out the resources required to realise these ambitions and provide a timeline for advances in the key areas.

physics.acc-ph↗

arXiv2019

Nano radiation detector: A possibility Making Physically Useful Nanostructures With Focused Ion Beam: A study of Nano Gaps

Child-Langmuir law expresses the IV relation between two parallel plates. It has been found that in reality the ordinary Child Langmuir Law does not hold true. It shows some geometric dependence on the system.In this report capacitors of various thickness and septation has been studied both in macro and nano scale to propose a geometrical correction to the law. More over from the studies, a new type of radiation detector was prepared which can detect radiation in small volumes as compared with normal radiation detectors.

physics.ins-det↗

arXiv2019

A Se vacancy induced localized Raman mode in two-dimensional MoSe2 grown by CVD

Defects play a significant role in optical properties of semiconducting two-dimensional transition metal dichalcogenides (TMDCs). In ultra-thin MoSe2, a remarkable feature at ~250 cm-1 in Raman spectra is ascribed to be a defect-related mode. Recent attempts failed to explain the origin of this peak, leaving it being a mystery. Here in this work, we demonstrate that this peak is a Se vacancy induced defect mode. Heat effect and hydrogen etching are two main factors to introduce Se vacancies in CVD process of growing MoSe2. A phonon confinement model can well explain the behaviors of intrinsic Raman modes. Density functional theory (DFT) calculation reveals that single Se vacancy (VSe) is responsible for the appearance of Raman peak at ~250 cm-1 and this mode is an A1g-like localized mode which is also confirmed by polarized Raman scattering experiment. The relative strength of this mode can be a characterization of the quality of 2D MoSe2. This work may offer a simple method to tailor chalcogenide vacancies in 2D TMDCs and provide a way to study their vibrational properties.

cond-mat.mtrl-sci↗

arXiv2019

Cryogenic MOSFET Threshold Voltage Model

This paper presents a physics-based model for the threshold voltage in bulk MOSFETs valid from room down to cryogenic temperature (4.2 K). The proposed model is derived from Poisson's equation including bandgap widening, intrinsic carrier-density scaling, and incomplete ionization. We demonstrate that accounting for incomplete ionization in the expression of the threshold voltage is critical for an accurate estimation of the current. The model is validated with our experimental results from nMOSFETs of a 28-nm CMOS process. The developed model is a key element for a cryo-CMOS compact model and can serve as a guide to optimize processes for high-performance cryo-computing and ultra-low-power quantum computing.

physics.app-ph↗

arXiv2019

Plasmonics Theory for Biosensor Design: Mathematical Formulations and Practical Applications

The last two decades have witnessed an exponential growth and tremendous developments in wireless technologies and systems, and their associated applications. In the recent years following 2006, there has been a great surge in interest in the newly emerging plasmonics nanotechnology because this new device technology provides tremendous synergy between electronic and photonic devices. Electronics devices are down-scalable up to the nanoscale size but have limited processor speed due to thermal and signal delay issues associated with electronic devices. On the other hand, photonic devices have extremely high speed and high data carrying capacity but are limited in size to the diffraction law such that the size of a photonic device should be equal to about half of its operational wavelength. The size mismatch between electronic devices and photonic devices inhibits the advantageous interfacing between these two device technologies and here plasmonics nanotechnology plays the important role of interfacing these two technologies. Plasmonics technology provides high speed interconnections with high data carrying capacity between nano-scale electronic devices opening a new field of research which is on-chip high speed nano-networks [28]. It is this great advantage of plasmonics technology that made it a very interesting technology for implementation for the design of a miniature real-time biosensor. In our plasmonic biosensor design, we utilized a subset of plasmonics technology which is surface plasmon wave generation in order to continuously monitor the concentration of a desired analyte.

physics.optics↗