Planar ring-shaped phononic crystal anchoring boundaries for enhancing the quality factor of Lamb mode resonators
We report the use of planar ring-shaped phononic crystals (PnCs) as anchor boundaries of very-high-frequency band piezoelectric-on-silicon Lamb moderesonators for the purpose of enhancing their quality factor (Q). Here, we exploit the acousticbandgap associated with the PnC anchoring boundaries to reduce acoustic energy leakage out of the micromechanicalresonator. The proposed approach provides greater mechanical robustness (by merit of interlocking the cells in a matrix) and the possibility of electrical routing through the PnC cells. We experimentally show enhancements inQ by a factor of three using the proposed approach...
Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: L. Binci, C. Tu, H. Zhu and J. E.-Y. Lee Source Type: research
Near-field radiative heat transfer between doped-Si parallel plates separated by a spacing down to 200 nm
Heat transfer between two objects separated by a nanoscale vacuum gap holds great promise especially in energy harvesting applications such as near-field thermophotovoltaic systems. However, experimental validation of nanoscale radiative heat transfer has been largely limited to tip-plate configurations due to challenges of maintaining small gap spacing over a relatively large area. Here, we reportmeasurements of heat transfer near roomtemperature between two 1 cm by 1 cmdoped-Si parallel plates, separated by a vacuum gap from about 200 nm to 780 nm. Themeasured strong near-field radiative transfer is in quantita...
Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: Jesse I. Watjen, Bo Zhao and Zhuomin M. Zhang Source Type: research
Imaging and spectromicroscopy of photocarrier electron dynamics in C60 fullerene thin films
We have employed a two-photon photoelectron emissionmicroscopy (2P-PEEM) to observe the photocarrier electrondynamics in an organic thin film of fullerene (C60) formed on a highly oriented pyrolytic graphite with aspatial resolution of ca. 135 nm. In this approach, photocarrier electrons in C60 single-layer islandsgenerated by the first pumpphoton are detected by the second probephoton. These spectromicroscopic observations conducted over a 100 × 100 nm2 region of C60 islands consistently reproduced the macroscopic two-photonphotoemission spectrum of fully covered C60monolayer film, where the energy of photocarr...
Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: Masahiro Shibuta, Kana Yamagiwa, Toyoaki Eguchi and Atsushi Nakajima Source Type: research
Modeling Verwey transition temperature of Fe3O4 nanocrystals
The Verwey transition in nanoscale is an important physicalproperty for Fe3O4nanocrystals and has attracted extensive attention in recent years. In this work, an analytic thermodynamicmodel without any adjusting parameters is developed to estimate the size and shape effects on modulating the Verwey transition temperature of Fe3O4nanocrystals. The results show that the Verwey transition temperature reduces with increasing shape parameterλ or decreasing sizeD. A good agreement between the prediction and the experimental data verified our physical insight that the Verwey transition of Fe3O4 can be directly related to the ato...
Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: Xiao bao Jiang, Bei bei Xiao, Hong yu Yang, Xiao yan Gu, Hong chao Sheng and Xing hua Zhang Source Type: research
Tunable electronic and magnetic properties of Cr2M ′C2T2 (M′ = Ti or V; T = O, OH or F)
Here we report on the magnetic properties and electronic structures of Cr2M ′C2T2 (M ′ = Ti, or V; T = O, OH, or F) systems investigated by means of first-principles calculations. Results indicate that Cr2M ′C2T2 can be nonmagnetic,anti-ferromagnetic, orferromagnetic and either a semiconductor or metal depending on the choice of M ′ and T and the through-bond coupling interactions that affect the arrangements of Cr2M ′C2T2 systems. It was found that Cr2TiC2O2 is nonmagnetic, Cr2TiC2F2 and Cr2TiC2(OH)2 areanti-ferromagnetic. Cr2VC2(OH)2, Cr2VC2F2, and Cr2VC2O2 areferromagnetic. The Curie temperatures of Cr...
Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: Jianhui Yang, Xumeng Zhou, Xuepiao Luo, Shaozheng Zhang and Liang Chen Source Type: research
Strain controlled valley filtering in multi-terminal graphene structures
Valley-polarizedcurrents can be generated by local straining of multi-terminalgraphene devices. The pseudo-magnetic field created by the deformation allowselectrons from only one valley to transmit, and acurrent ofelectrons from a single valley is generated at the opposite side of the locally strained region. We show that valley filtering is most effective with bumps of a certain height and width. Despite the fact that the highest contribution to the polarizedcurrent comes fromelectrons from the lowest sub-band, contributions of other sub-bands are not negligible and can significantly enhance the outputcurrent. (Source: Ap...
Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: S. P. Milovanovi ć and F. M. Peeters Source Type: research
Large scale arrays of four-state vortex domains in BiFeO3 thin film
Exotic domain states, likevortex, offer the promise of superior properties and the potentialdisclination strain is a key factor for their formation inferroelectrics. Here we show that large scale arrays of four-statevortex domains can be obtained in rhombohedral BiFeO3thin filmsgrown on PrScO3 substrates bypulsed laser deposition. Cs-corrected scanning transmission electron microscopy demonstrates that eachvortex domain is comprised of fourferroelectric variants with two 180 °domain walls and two 109 °domain walls. Atomic mappings of the lattice distortions unit cell by unit cell reveal that the cores of thevortex might ...
Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: W. Y. Wang, Y. L. Zhu, Y. L. Tang, Y. B. Xu, Y. Liu, S. Li, S. R. Zhang, Y. J. Wang and X. L. Ma Source Type: research
Voltage-impulse-induced dual-range nonvolatile magnetization modulation in metglas/PZT heterostructure
Dual-range, nonvolatilemagnetization modulation induced by voltage impulses was investigated in the metglas/lead zirconate titanate(PZT)heterostructure at room temperature. Theheterostructure was obtained by bonding a square metglas ribbon on the top electrode of thePZT substrate, which contained defect dipoles resulting from acceptordoping. ThePZT substrate achieved two strain hysteretic loops with the application of specific voltage impulse excitation modes. Through strain-mediatedmagnetoelectric coupling between the metglas ribbon and thePZT substrate, two strain hysteretic loops led to a dual-range nonvolatilemagnetiza...
Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: Xiaoli Tang, Hua Su, Huaiwu Zhang and Nian X. Sun Source Type: research
Spin-torque ferromagnetic resonance measurements utilizing spin Hall magnetoresistance in W/Co40Fe40B20/MgO structures
This study takes the advantage of the spin Hallmagnetoresistance (SMR) for generating an oscillating resistance, which is one of the necessary requirements for obtaining mixing voltage in the ST-FMR technique. We have measured both the as-grown and theannealed samples with different CoFeB layer thicknesses, which include the in-plane and out-of-planemagnetic anisotropies. The spectra for these two types ofanisotropies show distinct signatures. By analyzing the ST-FMR spectra, we extract the effectiveanisotropy field for both types of samples. In addition, we investigate the influence of CoFeB thickness andannealing on the ...
Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: Congli He, Aryan Navabi, Qiming Shao, Guoqiang Yu, Di Wu, Weihua Zhu, Cheng Zheng, Xiang Li, Qing Lin He, Seyed Armin Razavi, Kin L. Wong, Zongzhi Zhang, Pedram Khalili Amiri and Kang L. Wang Source Type: research
Growth and characterization of TbAs films
We report on the molecular beam epitaxygrowth and characterization of TbAsfilms.In situreflection high energy electron diffraction andex situ high resolution X-ray diffraction, reciprocal space mapping, and both scanning andtransmission electron microscopy are used to confirm the completefilmgrowth and study thefilms' morphology. Spectrophotometry measurements provide the energy of optical transitions, revealing a red shift in optical band gap with increasing thickness. The Hall effect measurements show temperature insensitivecarrier concentrations, resistivities, and mobilities. Thecarrier concentration decreases and resi...
Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: Cory C. Bomberger, Bo E. Tew, Matthew R. Lewis and Joshua M. O. Zide Source Type: research
Lattice vibrations and electrical transport in (Bi1 −xInx)2Se3 films
We present Raman, terahertz transmission, and transport measurements on (Bi1 −xInx)2Se3films to study the evolution ofphonon modes andresistivity with an increasingindium content across themetal-insulator phase transition. The frequencies of two Raman-active modesEg2 andA1g2 as well as an infrared-active modeEu increase with an increasingindium content due to the smaller atomic weight ofindium compared to bismuth. Terahertz data are fitted by a Drude-Lorentz model. Drude scattering rates increase from 47 to 75 cm−1 with an increasingindium content from 0% to 16% due to stronger impurity scattering. Thecarrier concen...
Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: Jiajun Zhu, Fang Liu, Shengqiang Zhou, C. Franke, S. Wimmer, V. V. Volobuev, G. Springholz, A. Pashkin, H. Schneider and M. Helm Source Type: research
Nanodiamond embedded ta-C composite film by pulsed filtered vacuum arc deposition from a single target
DetonationNanodiamonds (DNDs) are known to have sp3 core, sp2 shell, small size (few nm) and are gaining importance as multi-functional nanoparticles. Diverse methods have been used to form composites, containing detonationnanodiamonds (DNDs) embedded in conductive and dielectric matrices for various applications. Here we show a method, wherein DND-ta-C compositefilm, consisting of DNDs embedded in ta-C matrix have been co-deposited from the samecathode by pulsed filtered cathodic vacuum arc method. Transmission Electron Microscope analysis of thesefilms revel the presence of DNDs embedded in the matrix of amorphouscarbon....
Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: Ajai Iyer, Jarkko Etula, Yanling Ge, Xuwen Liu and Jari Koskinen Source Type: research
High performance photodetector based on Pd-single layer MoS2 Schottky junction
Due to excellent photoelectric property of single layer molybdenum disulphide (SL MoS2), different kinds ofphotodetectors based on SL MoS2 have been reported. Although high photosensitivity was obtained, the rising and decay time ofphotocurrent were relatively large (>300 ms) when the current reached up toμA order. In this paper, we demonstrate a high sensitive and fast barrier typephotodetector based on Pd-SL MoS2Schottky junction. The photosensitivity can reach up to 0.88 A/W at 425 nm laser. Compared with SL MoS2photodetectors based onohmic contact, our device shows much shorter rising and a decay time of 24.7 ...
Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: Xue-Feng Wang, Hai-Ming Zhao, Shu-Hong Shen, Yu Pang, Peng-Zhi Shao, Yu-Tao Li, Ning-Qin Deng, Yu-Xing Li, Yi Yang and Tian-Ling Ren Source Type: research
Achieving bifunctional cloak via combination of passive and active schemes
In this study, a simple and delicate approach to realizing manipulation of multi-physics field simultaneously through combination of passive and active schemes is proposed. In the design, one physical field is manipulated with passive scheme while the other with active scheme. As a proof of this concept, a bifunctional device is designed and fabricated to behave as electric and thermal invisibility cloak simultaneously. It is found that the experimental results are consistent with the simulated ones well, confirming the feasibility of our method. Furthermore, the proposed method could also be extended to other multi-physic...
Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: Chuwen Lan, Ke Bi, Zehua Gao, Bo Li and Ji Zhou Source Type: research
Secondary electron emission from plasma-generated nanostructured tungsten fuzz
Recently, several researchers [e.g., Yanget al., Sci. Rep.5, 10959 (2015)] have shown thattungsten fuzz can grow on a hottungstensurface under bombardment by energetic helium ions in different plasma discharges and applications, including magnetic fusion devices with plasma facingtungsten components. This work reports the directmeasurements of the total effectivesecondary electron emission (SEE) fromtungsten fuzz. Using dedicated materialsurfacediagnostics andin-situ characterization, we find two important results: (1) SEE values fortungsten fuzz are 40% –63% lower than for smoothtungsten and (2) the SEE values fortungst...
Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: M. Patino, Y. Raitses and R. Wirz Source Type: research
