Applied Physics Letters, published by the American Institute of Physics, features concise, up-to-date reports on significant new findings in applied physics. Emphasizing rapid dissemination of key data and new physical insights, Applied Physics Letters offers prompt publication of new experimental and theoretical papers bearing on applications of physics phenomena to all branches of science, engineering, and modern technology. Content is published online daily, collected into weekly online and printed issues (52 issues per year).
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Recent interest in flexible electronics and wearable devices has created a demand for fast and highly repeatable printing processes suitable for device manufacturing. Robust printing technology is critical for the integration of sensors and other devices on flexible substrates such as paper and textile. An atmospheric pressure plasma-based printing process has been developed to deposit different types of nanomaterials on flexible substrates. Multiwalled carbon nanotubes were deposited on paper to demonstrate site-selective deposition as well as direct printing without any type of patterning. Plasma-printed nanotubes were compared with non-plasma-printed samples under similar gas flow and other experimental conditions and found to be denser with higher conductivity. The utility of the nanotubes on the paper substrate as a biosensor and chemical sensor was demonstrated by the detection of dopamine, a neurotransmitter, and ammonia, respectively.
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Rare earth oxides are usually widegap insulators like Y2O3 with closed shell trivalent rare earth ions. In this study, solid phase rock salt structure yttrium monoxide, YO, with unusual valence of Y2+ (4d1) was synthesized in a form of epitaxialthin film by pulsed laser deposition method. YO has been recognized as gaseous phase in previous studies. In contrast with Y2O3, YO was dark-brown colored and narrow gap semiconductor. The tunable electrical conductivity ranging from 10−1 to 103 Ω−1 cm−1 was attributed to the presence of oxygen vacancies serving as electron donor. Weak antilocalization behavior observed in magnetoresistance indicated significant role of spin-orbit coupling as a manifestation of 4d electron carrier.
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The spin currenttransport property in a ceramic material TiN has been investigated at room temperature. By attaching TiN thin films on Ni20Fe80 with different thicknesses of TiN, the spin pumping experiment has been conducted, and the spin diffusion length in TiN was measured to be around 43 nm. Spin-torque ferromagnetic resonance has also been taken to investigate the spin Hall angle of TiN, which was estimated to be around 0.0052. This study on ceramic material provides a potential selection in emerging materials for spintronics application.
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This paper reports non-trivial effects of the ionic purity of nanoparticles on the concentration of ions in liquid crystals.Nanoparticles dispersed in liquid crystals can affect the concentration of mobile ions in different ways. 100% pure nanoparticles can only decrease the concentration of ions by means of adsorption/desorption processes. Liquid crystals doped with contaminated nanoparticles exhibit three regimes, namely, the purification, contamination, and no change in the concentration of ions. Switching between these regimes is governed by three dominant factors: the purity of liquid crystals, the purity of nanoparticles, and the ratio of the adsorption rate to the desorption rate.
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We present a rapid-scan, time-domain terahertz spectrometer employing femtosecond Er:fiber technology and an acousto-optic delay with attosecond precision, enabling scanning of terahertz transients over a 12.4-ps time window at a waveform refresh rate of 36 kHz, and a signal-to-noise ratio of 1.7 × 105. Our approach enables real-time monitoring of dynamic THz processes at unprecedented speeds, which we demonstrate through rapid 2D thickness mapping of a spinning teflon disc at a precision of 10 nm/. The compact, all-optical design ensures alignment-free operation even in harsh environments.
Latest Articles
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Robust acoustic wave manipulation of bubbly liquids
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Experiments with water–air bubbly liquids when exposed to acoustic fields of frequency ∼100 kHz and intensity below the cavitation threshold demonstrate that bubbles ∼30 μm in diameter can be “pushed” away from acoustic sources by acoustic radiation independently from the direction of gravity. This manifests formation and propagation of acoustically induced transparency waves(waves of the bubble volume fraction). In fact, this is a collective effect of bubbles, which can be described by a mathematical model of bubble self-organization in acoustic fields that matches well with our experiments.
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Achieving thermal rectification in designed liquid-liquid systems
Thermal rectification is generally implemented using solid structures. We demonstrate how thermal transport can be rectified using designed liquid-liquid structures consisting of thin adjacent immiscible water and hexane layers. For specified hot and cold side temperatures, the heat flux differs when either water or hexane is placed on the hot side, demonstrating thermal rectification between the two cases. The rectification is influenced by the relative thicknesses of the layers. It is the highest when the water-hexane interface temperatures for both cases are identical. Changing the thermal conductivity of hexane, which is the lower thermal conductivity liquid, e.g., by potentially loading it with conducting or insulating nanoparticles, has a larger impact on rectification than altering the waterconductivity, which is higher. If interfacial temperature discontinuities can be engineered across macroscale interfaces as is natural for nanoscale systems, these also lead to significant increase in rectification.
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Observation of a scrolled graphene nanoribbons with gap-plasmonic system
We report an observation of a scrolled graphene nanoribbon (sGNR) produced via a chemical vapor deposition. The sandwiched sGNR between Au nanoparticle and Au thin film system can be identified by the remarkable enhancement of G peak accompanied with a subsequent splitting (G+ and G−) with strong Radial Breading Like Mode enhancement. Because the weak adhesion force between graphene monolayer and target Au substrate during transfer maybe result in a sparse distribution of sGNR with a z-directional curvature-induced G peak splitting. Reproducibility and mass production with a nanometer scale circuit devices may be anticipated from this work.
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Visualization of dielectric constant-electric field-temperature phase maps for imprinted relaxor ferroelectric thin films
The dielectricphase transition behavior of imprinted lead magnesium niobate–lead titanate relaxor ferroelectricthin films was mapped as a function of temperature and dc bias. To compensate for the presence of internal fields, an external electric bias was applied while measuring dielectric responses. The constructed three-dimensional dielectric maps provide insight into the dielectric behaviors of relaxor ferroelectricfilms as well as the temperature stability of the imprint. The transition temperature and diffuseness of the dielectric response correlate with crystallographic disorder resulting from strain and defects in the films grown on strontium titanate and silicon substrates; the latter was shown to induce a greater degree of disorder in the film as well as a dielectric response lower in magnitude and more diffuse in nature over the same temperature region. Strong and stable imprint was exhibited in both films and can be utilized to enhance the operational stability of piezoelectric devices through domain self-poling.
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Internal electrical and strain fields influence on the electrical tunability of epitaxial Ba0.7Sr0.3TiO3 thin films
Perpetual demand for higher transfer speed and ever increasing miniaturization of radio and microwave telecommunication devices demands new materials with high electrical tunability. We have investigated built in electrical and strain fields' influence on the electrical tunability in Ba0.7Sr0.3TiO3thin film hetero-system grown by pulsed laser deposition technique. We observed the built in electrical field by local piezo-force microscopy (as deflected hysteresis loops) and macroscopic impedance analysis (as asymmetric tunability curves), with the calculated 88 kV/cm built in field at room temperature. Negative −1.4% misfit strain (due to clamping by the substrate) enhanced ferroelectric phase transition temperature in Ba0.7Sr0.3TiO3thin film by more than 300 K. Built in fields do not deteriorate functional film properties—dielectric permittivity and tunability are comparable to the best to date values observed in Ba1−xSrxTiO3thin films.
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Gate-controlled switching between persistent and inverse persistent spin helix states
We demonstrate gate-controlled switching between persistent spin helix (PSH) state and inverse PSH state, which are detected by quantum interference effect on magneto-conductance. These special symmetric spin states showing weak localization effect give rise to a long spin coherence when the strength of Rashba spin-orbit interaction(SOI) is close to that of Dresselhaus SOI. Furthermore, in the middle of two persistent spin helix states, where the Rashba SOI can be negligible, the bulk Dresselhaus SOI parameter in a modulation doped InGaAs/InAlAs quantum well is determined.
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