Magnetic anisotropy at the buried CoO/Fe interface
Interfaces between antiferromagnetic CoO and ferromagnetic Fe are typically characterized by the development of Fe oxides. Recently, it was shown that the use of a proper ultra-thin Cobuffer layer prevents the formation of Fe oxides [Brambillaet al., Appl. Surf. Sci.362, 374 (2016)]. In the present work, we investigate the magneticproperties of such aninterface, and we find evidence for an in-plane uniaxialmagnetic anisotropy, which is characterized by a multijump reversal behavior in the magnetizationhysteresis loops.X-ray photoemission spectroscopy and element-sensitivehysteresis loops reveal that the occurrence of such ...
Source: Applied Physics Letters - December 5, 2016 Category: Physics Authors: D. Giannotti, H. Hedayat, G. Vinai, A. Picone, A. Calloni, G. Berti, M. Riva, G. Bussetti, F. Boschini, P. Torelli, G. Panaccione, E. Carpene, C. Dallera, M. Finazzi and A. Brambilla Source Type: research
Characterization of Mg and Fe doped Sb2Se3 thin films for photovoltaic application
Sb2Se3 holds a great potential for low-cost thin film photovoltaics because of its very attractivematerial and optoelectronicproperties, and the demonstrated 5.6% certified efficiency and decentdevice stability. A full understanding of the influence of external impurities on theproperties ofSb2Se3 films would help the further improvement ofSb2Se3solar cells. In this work, we carefully characterized theMg and Fedoping inSb2Se3 films. Both Kelvin probe force microscope and Hallmeasurements revealed thatMg was largely inert while Fe introduced the n-typedoping.Temperature-dependentconductivity and admittance further demonstra...
Source: Applied Physics Letters - December 5, 2016 Category: Physics Authors: Yang Li, Ying Zhou, Yining Zhu, Chao Chen, Jiajun Luo, Jingyuan Ma, Bo Yang, Xiaojie Wang, Zhe Xia and Jiang Tang Source Type: research
Local carrier recombination and associated dynamics in m-plane InGaN/GaN quantum wells probed by picosecond cathodoluminescence
We report on spatially resolved and time-resolvedcathodoluminescence(CL) studies of the recombination mechanisms of InGaN/GaNquantum wells(QWs) grown by metal-organic vapour phase epitaxy on bulkm-plane AmmonoGaN substrates. As a result of the 2 ° miscut of theGaN substrate, the sample surface exhibits step bunches, where semi-polarQWs with a higherindium concentration than the planarm-planeQWs form during theQW growth. Spatially resolved time-integratedCL maps under both continuous and pulsed excitation show a broad emission band originating from them-planeQWs and a distinct low energy emission originating from the semi-...
Source: Applied Physics Letters - December 5, 2016 Category: Physics Authors: Tongtong Zhu, David Gachet, Fengzai Tang, Wai Yuen Fu, Fabrice Oehler, Menno J. Kappers, Phil Dawson, Colin J. Humphreys and Rachel A. Oliver Source Type: research
Optical reflectivity and hardness improvement of hafnium nitride films via tantalum alloying
It is found that incorporation oftantalum in a hafnium nitridefilm induces a tunable opticalreflectivity and improves thehardness. The underlying mechanism can be illustrated by a combination of experiments andfirst-principles calculations. It is shown that the evolution of opticalreflectivity and the increase inhardness arise from the formation of Hf1 −xTaxNsolid solutions and the resulting changes in the electronic structure. The increase in infrared reflectance originates from the increase in concentration of freeelectrons (n) becauseTa (d3s2) has one more valenceelectron than Hf (d2s2). The sharp blue-shift in cutoff...
Source: Applied Physics Letters - December 5, 2016 Category: Physics Authors: Zhiqing Gu, Haihua Huang, Sam Zhang, Xiaoyi Wang, Jing Gao, Lei Zhao, Weitao Zheng and Chaoquan Hu Source Type: research
Improved interface properties of GaN metal-oxide-semiconductor device with non-polar plane and AlN passivation layer
Utilizing a non-polar plane substrate and an ultra-thinAlNpassivation layer results in significantly improvedinterfaceproperties of aGaN metal-oxide-semiconductor (MOS) device. After depositing an Al2O3 gatedielectric layer onGaN substrates with polar c-plane and non-polar m-plane surfaces, it is found that the devices on the non-polar surface show much betterinterfaceproperties than those on the polar surface. To further improve theinterfaceproperties, an amorphous ultra-thinAlN layer is deposited on the substrate before the Al2O3 deposition. Theinterfaceproperties of both devices on the c-plane and m-plane are dramatical...
Source: Applied Physics Letters - December 5, 2016 Category: Physics Authors: Xian Wu, Renrong Liang, Lei Guo, Lei Liu, Lei Xiao, Shanshan Shen, Jun Xu and Jing Wang Source Type: research
Thermal rectification in inhomogeneous nanotubes
Heat transfer in axially inhomogeneousnanotubes is known to be asymmetric with respect to the direction of transfer. This phenomenon is known as the thermalrectification. We demonstrate that thermalrectification in suchnanotubes arises due to the interference ofphonons excited in the different parts of thenanotube. It is shown that therectification does not vanish when the thickness ofnanotube increases, but it vanishes as the external diameter ofnanotubes decreases to a few nanometers. The understanding of the origin of thermalrectification opens a way to the design of devices controlling heat flows that could perform as ...
Source: Applied Physics Letters - December 5, 2016 Category: Physics Authors: Bair V. Budaev and David B. Bogy Source Type: research
Heterogeneous nucleation and heat flux avalanches in La(Fe, Si)13 magnetocaloric compounds near the critical point
The phase transformation kinetics of LaFe11.41Mn0.30Si1.29-H1.65 magnetocaloric compound is addressed by low ratecalorimetry experiments. Scans at 1 mK/s show that its first order phase transitions are made by multiple heat fluxavalanches. Getting very close to thecritical point, when thetransition becomes of the second order type, the step-like discontinuous behaviour associated withavalanches is smoothed out and the thermalhysteresis disappears. This result is confirmed by magneto-resistivitymeasurements and allows to obtain accurate values of the temperaturehysteresis ( ΔThyst = 0.37 K) at zero externalmagnetic f...
Source: Applied Physics Letters - December 5, 2016 Category: Physics Authors: C. Bennati, L. Gozzelino, E. S. Olivetti and V. Basso Source Type: research
Temperature coefficients of crystalline-quartz elastic constants over the cryogenic range [4 K, 15 K]
This paper brings out the temperature coefficients of synthetic-quartzelastic constants atliquid helium temperature. The method is based on the relationship between theresonance frequencies of aquartz acoustic cavity and theelastic constants of the material. The temperature coefficients of theelastic constants are extracted from experimental frequency-temperature data collected within the very usefulcryogenic range [4 K–15 K] from a set ofresonators of various cut angles, because of theanisotropy ofquartz. (Source: Applied Physics Letters)
Source: Applied Physics Letters - December 5, 2016 Category: Physics Authors: J érémy Bon, Serge Galliou and Roger Bourquin Source Type: research
Local heterogeneity in the mechanical properties of bicontinuous composites made by liquid metal dealloying
In this study, we use statistically significantnanoindentation to characterize the mechanical properties of individual phases in dealloyed bicontinuouscomposites. Through theanalysis of several thousand indents, we correlate variances in thehardness andelastic modulus directly with the local microstructure and composition of thematerial. (Source: Applied Physics Letters)
Source: Applied Physics Letters - December 5, 2016 Category: Physics Authors: Ian McCue, Bernard Gaskey, Bryan Crawford and Jonah Erlebacher Source Type: research
On the motion of a sessile drop on an incline: Effect of non-monotonic thermocapillary stresses
We studied the short-time contact-linedynamics of a self-rewetting sessiledroplet sliding “freely” on a silicone oil layer, on an inclined, uniformly heated substrate under non-isothermal conditions(liquid –solid). The effect of thermocapillarity and the contribution ofsurface tension gradients(Marangoni effect) to thedroplet motion was investigated. The temperature of the substrate in conjunction with the non-monotonicsurface tension/temperature dependence of the deformed self-rewettingdroplet was found to significantly affect the early-stage inertial-capillary spreading regime. Infrared (IR) thermography images wer...
Source: Applied Physics Letters - December 5, 2016 Category: Physics Authors: Dimitrios Mamalis, Vasileios Koutsos and Khellil Sefiane Source Type: research
Shape-adaptable hyperlens for acoustic magnifying imaging
Previous prototypes of acoustic hyperlens consist of rigid channels, which are unable to adapt in shape to the object under detection. We propose to overcome this limitation by employing softplastic tubes that could guide acoustics with robustness againstbendingdeformation. Based on the idea of soft-tube acoustics, acoustic magnifying hyperlens with planar input and output surfaces has been fabricated and validated experimentally. The shape-adaption capability of the soft-tube hyperlens is demonstrated by a controlled experiment, in which the magnifying super-resolutionimages remain stable when the lens input surface is cu...
Source: Applied Physics Letters - December 2, 2016 Category: Physics Authors: Hongkuan Zhang, Xiaoming Zhou and Gengkai Hu Source Type: research
Thermomechanical response of thermoelectrics
We have theoretically investigated the product ofelastic modulus and linear coefficient ofthermal expansion for 20 thermoelectrics. The product is inversely proportional to equilibrium volume, which is consistent with the Debye-Gr üneisen model. Oxides exhibit larger products, while the products of Te-containing thermoelectrics are considerably smaller. This is likely due to strong bonding in these oxides, which makes them prone to thermal stress, thermal shock, and thermal fatigue. As this product is rarely available in lit erature and the equilibrium volume is easily measurable, this work provides a quick estimation for...
Source: Applied Physics Letters - December 2, 2016 Category: Physics Authors: Denis Music, Richard W. Geyer and Philipp Keuter Source Type: research
The antiphase boundary in half-metallic Heusler alloy Co2Fe(Al,Si): atomic structure, spin polarization reversal, and domain wall effects
Atomic resolution scanning transmission electron microscopy reveals the presence of an antiphase boundary in the half-metallic Co2Fe(Al,Si) full Heusler alloy. By employing thedensity functional theory calculations, we show that this defect leads to reversal of the sign of the spin-polarization in the vicinity of the defect. In addition, we show that this defect reduces the strength of theexchange interactions, without changing theferromagnetic ordering across the boundary. Atomistic spin calculations predict that this effect reduces the width of themagnetic domain wall compared to that in the bulk. (Source: Applied Physics Letters)
Source: Applied Physics Letters - December 2, 2016 Category: Physics Authors: Zlatko Nedelkoski, Ana M. Sanchez, Arsham Ghasemi, Kohei Hamaya, Richard F. L. Evans, Gavin R. Bell, Atsufumi Hirohata and Vlado K. Lazarov Source Type: research
Minority carrier recombination of ordered Ga0.51In0.49P at high temperatures
The minoritycarrier lifetime of high-quality ordered GaInP lattice matched toGaAs and the surface recombination velocity at its interface to AlInP weremeasured using time-resolved photo-luminescence in thetemperature range of77–500 K. The surface recombination velocity was found to be relatively low (under 500 cm/s) over themeasuredtemperature range. The effective lifetime increased with atemperature up to around 300 K, and then decreased in the300–500 K range. The variations in the effective lifetime, caused by the variations in the bulk lifetime, are explained by considering the separate contributions ...
Source: Applied Physics Letters - December 2, 2016 Category: Physics Authors: R. Dagan, Y. Rosenwaks, A. Kribus, A. W. Walker, J. Ohlmann and F. Dimroth Source Type: research
Modeling and experimental verification of an ultra-wide bandgap in 3D phononic crystal
This paper reports a comprehensivemodeling and experimental characterization of a three-dimensional phononic crystal composed of a single material, endowed with an ultra-wide completebandgap. The phononicband structure shows a gap-mid gap ratio of 132% that is by far the greatest full 3Dbandgap in literature for any kind of phononic crystals. A prototype of the finitecrystal structure has been manufactured in polyamide by means of additive manufacturing technology and tested to assess the transmission spectrum of the crystal. The transmission spectrum has been numerically calculated taking into account a frequency-dependen...
Source: Applied Physics Letters - December 2, 2016 Category: Physics Authors: L. D'Alessandro, E. Belloni, R. Ardito, A. Corigliano and F. Braghin Source Type: research
