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7 Feb 2013

Volume 113, Issue 5, Articles (05xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 113, 051101 (2013); http://dx.doi.org/10.1063/1.4769968 (11 pages)

J. M. Dallesasse and N. Holonyak, Jr.
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Oxidation of Al-bearing III-V materials: A review of key progress

J. M. Dallesasse and N. Holonyak, Jr.

J. Appl. Phys. 113, 051101 (2013); http://dx.doi.org/10.1063/1.4769968 (11 pages)

Online Publication Date: 1 February 2013

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Since the discovery of III-V oxidation by Dallesasse and Holonyak in 1989, significant progress has been made both technically and commercially in the use of oxides in compound semiconductor devices. Devices ranging from lasers to transistors have been fabricated that capitalize on the process-induced modification of refractive index and conductivity, allowing control of the two carriers of information in opto-electronic systems—the photon and the electron. Of particular note has been the use of oxidation for the fabrication of high-speed vertical-cavity surface-emitting lasers, which have extensive use in optical data links found in enterprise networks, data centers, and supercomputing applications. The discovery of III-V oxidation and key technical milestones in the fabrication of photonic and electronic devices that use oxidation are reviewed.
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81.65.Mq Oxidation
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
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back to top Lasers, Optics, and Optoelectronics

Efficient end-fire coupling of surface plasmons on flat metal surfaces for improved plasmonic Mach-Zehnder interferometer

Haifeng Hu, Xie Zeng, Dengxin Ji, Lin Zhu, and Qiaoqiang Gan

J. Appl. Phys. 113, 053101 (2013); http://dx.doi.org/10.1063/1.4789809 (5 pages)

Online Publication Date: 1 February 2013

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An efficient on-chip coupling mechanism is essential for nanoplasmonic circuits and elements. We show theoretically that end-fire coupling is a promising candidate to deliver light into regions with subwavelength dimension on flat metal surfaces. A design and optimization principle is presented for a flat metal surface and further demonstrated in a plasmonic Mach-Zehnder interferometer platform. The physical mechanism is discussed based on reciprocity. By considering the radiation pattern and position of the incidence, the coupling efficiency at the metal/air interface can be enhanced up to 77.6%–95.4%, which is promising to develop energy-efficient applications for on-chip plasmonic waveguide networks and sensors.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
07.60.Ly Interferometers

Giant enhancement of phonon-assisted one-photon excited frequency upconversion in a Nd3+-doped tellurite glass

M. S. Marques, L. de S. Menezes, W. Lozano B., L. R. P. Kassab, and C. B. de Araújo

J. Appl. Phys. 113, 053102 (2013); http://dx.doi.org/10.1063/1.4789965 (4 pages)

Online Publication Date: 1 February 2013

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Changing the sample's temperature from 200 K to 535 K, we observed 670-fold enhancement of a phonon-assisted upconversion emission at ≈754 nm obtained from a Nd3+-doped tellurite glass excited by 5 ns laser pulses at 805 nm. A rate-equation model, including the relevant energy levels and temperature dependent transition rates, is proposed to describe the process. The results fit well with the data when one considers the nonradiative transitions contributing for the 754 nm luminescence are promoted by an effective phonon mode with energy of 700 cm−1.
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78.55.Qr Amorphous materials; glasses and other disordered solids
63.20.dd Measurements

Strong heavy-to-light hole intersubband absorption in the valence band of carbon-doped GaAs/AlAs superlattices

M. I. Hossain, Z. Ikonic, J. Watson, J. Shao, P. Harrison, M. J. Manfra, and O. Malis

J. Appl. Phys. 113, 053103 (2013); http://dx.doi.org/10.1063/1.4790305 (5 pages)

Online Publication Date: 1 February 2013

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We report strong mid-infrared absorption of in-plane polarized light due to heavy-to-light hole intersubband transitions in the valence band of C-doped GaAs quantum wells with AlAs barriers. The transition energies are well reproduced by theoretical calculations including layer inter-diffusion. The inter-diffusion length was estimated to be 8 ± 2 Å, a value that is consistent with electron microscopy measurements. These results highlight the importance of modeling the nanoscale structure of the semiconductors for accurately reproducing intra-band transition energies of heavy carriers such as the holes.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
81.07.St Quantum wells
66.30.Ny Chemical interdiffusion; diffusion barriers
71.20.Nr Semiconductor compounds
78.30.Fs III-V and II-VI semiconductors
78.67.De Quantum wells

Full-field transmission x-ray imaging with confocal polycapillary x-ray optics

Tianxi Sun and C. A. MacDonald

J. Appl. Phys. 113, 053104 (2013); http://dx.doi.org/10.1063/1.4789799 (4 pages)

Online Publication Date: 4 February 2013

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A transmission x-ray imaging setup based on a confocal combination of a polycapillary focusing x-ray optic followed by a polycapillary collimating x-ray optic was designed and demonstrated to have good resolution, better than the unmagnified pixel size and unlimited by the x-ray tube spot size. This imaging setup has potential application in x-ray imaging for small samples, for example, for histology specimens.
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07.85.-m X- and γ-ray instruments

A microlens array based on polymer network liquid crystal

Miao Xu, Zuowei Zhou, Hongwen Ren, Seung Hee Lee, and Qionghua Wang

J. Appl. Phys. 113, 053105 (2013); http://dx.doi.org/10.1063/1.4790303 (6 pages)

Online Publication Date: 4 February 2013

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multimedia

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Using UV light to expose a homogeneous cell containing liquid crystal (LC)/monomer mixture through a patterned photomask, we prepared a polymer network liquid crystal (PNLC) microlens array. In each microlens, the formed polymer network presents a central-symmetrical inhomogeneous morphology and LC exhibits a gradient refractive index distribution. By applying an external voltage to the cell, the gradient of the LC refractive index is changed. As a result, the focal length of the microlens can be tuned. Our PNLC microlens array has the advantages of low operating voltage, easy fabrication, and good stability. This kind of microlens array has potential applications in image processing, optical communications, and switchable 2D/3D displays.
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42.79.Bh Lenses, prisms and mirrors
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.70.Df Liquid crystals
42.70.Jk Polymers and organics

Suppression of spatial hole burning and pulse stabilization for actively modelocked quantum cascade lasers using quantum coherent absorption

S. S. Shimu, A. Docherty, M. A. Talukder, and C. R. Menyuk

J. Appl. Phys. 113, 053106 (2013); http://dx.doi.org/10.1063/1.4790145 (5 pages)

Online Publication Date: 5 February 2013

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We theoretically study of an actively modelocked quantum cascade laser in which we incorporate quantum coherent absorption by interleaving quantum coherent absorbing periods with gain periods. We show that this absorption suppresses the spatial hole burning that is responsible for pulse instability. As a consequence, the laser produces a stable train of single-peak soliton-like pulses with pulse durations less than 1.25 ps over a broad range of pump powers. We also show that the laser self-starts from initial quantum noise.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
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Nonlinear bleaching, absorption, and scattering of 532-nm-irradiated plasmonic nanoparticles

V. Liberman, M. Sworin, R. P. Kingsborough, G. P. Geurtsen, and M. Rothschild

J. Appl. Phys. 113, 053107 (2013); http://dx.doi.org/10.1063/1.4790798 (10 pages)

Online Publication Date: 6 February 2013

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Single-pulse irradiation of Au and Ag suspensions of nanospheres and nanodisks with 532-nm 4-ns pulses has identified complex optical nonlinearities while minimizing material damage. For all materials tested, we observe competition between saturable absorption (SA) and reverse SA (RSA), with RSA behavior dominating for intensities above ∼50 MW/cm2. Due to reduced laser damage in single-pulse experiments, the observed intrinsic nonlinear absorption coefficients are the highest reported to date for Au nanoparticles. We find size dependence to the nonlinear absorption enhancement for Au nanoparticles, peaking in magnitude for 80-nm nanospheres and falling off at larger sizes. The nonlinear absorption coefficients for Au and Ag spheres are comparable in magnitude. On the other hand, the nonlinear absorption for Ag disks, when corrected for volume fraction, is several times higher. These trends in nonlinear absorption are correlated to local electric field enhancement through quasi-static mean-field theory. Through variable size aperture measurements, we also separate nonlinear scattering from nonlinear absorption. For all materials tested, we find that nonlinear scattering is highly directional and that its magnitude is comparable to that of nonlinear absorption. These results indicate methods to improve the efficacy of plasmonic nanoparticles as optical limiters in pulsed laser systems.
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81.05.Bx Metals, semimetals, and alloys
81.07.-b Nanoscale materials and structures: fabrication and characterization
82.70.Kj Emulsions and suspensions
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
back to top Plasmas and Electrical Discharges

Direct evidence of mismatching effect on H emission in laser-induced atmospheric helium gas plasma

Zener Sukra Lie, May On Tjia, Rinda Hedwig, Maria Margaretha Suliyanti, Syahrun Nur Abdulmadjid, Nasrullah Idris, Alion Mangasi Marpaung, Marincan Pardede, Eric Jobiliong, Muliadi Ramli, Heri Suyanto, Kenichi Fukumoto, Kiichiro Kagawa, and Koo Hendrik Kurniawan

J. Appl. Phys. 113, 053301 (2013); http://dx.doi.org/10.1063/1.4789817 (6 pages)

Online Publication Date: 1 February 2013

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A time-resolved orthogonal double pulse laser-induced breakdown spectroscopy (LIBS) with helium surrounding gas is developed for the explicit demonstration of time mismatch between the passage of fast moving impurity hydrogen atoms and the formation of thermal shock wave plasma generated by the relatively slow moving major host atoms of much greater masses ablated from the same sample. Although this so-called “mismatching effect” has been consistently shown to be responsible for the gas pressure induced intensity diminution of hydrogen emission in a number of LIBS measurements using different ambient gases, its explicit demonstration has yet to be reported. The previously reported helium assisted excitation process has made possible the use of surrounding helium gas in our experimental set-up for showing that the ablated hydrogen atoms indeed move faster than the simultaneously ablated much heavier major host atoms as signaled by the earlier H emission in the helium plasma generated by a separate laser prior to the laser ablation. This conclusion is further substantiated by the observed dominant distribution of H atoms in the forward cone-shaped target plasma.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.25.Vy Impurities in plasmas
52.35.Tc Shock waves and discontinuities
52.38.Mf Laser ablation
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Two-dimensional space-resolved emission spectroscopy of laser ablation plasma in water

Ayumu Matsumoto, Ayaka Tamura, Kazuhiro Fukami, Yukio H. Ogata, and Tetsuo Sakka

J. Appl. Phys. 113, 053302 (2013); http://dx.doi.org/10.1063/1.4789968 (7 pages) | Cited 1 time

Online Publication Date: 4 February 2013

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We developed a method for two-dimensional space-resolved emission spectroscopy of laser-induced plasma in water to investigate the spatial distribution of atomic species involved in the plasma. Using this method, the laser ablation plasma produced on a Cu target in 5 mM NaCl aqueous solution was examined. The emission spectrum varied considerably depending on the detecting position. The temperature and the atomic density ratio NNa/NCu at various detecting positions were evaluated by fitting emission spectra to a theoretical model based on the Boltzmann distribution. We are successful in observing even a small difference between the distributions of the plasma parameters along the directions vertical and horizontal to the surface. The present approach gives direct information for sound understanding of the behavior of laser ablation plasma produced on a solid surface in water.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.38.Mf Laser ablation
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Evaluation of field emission parameters in a copper nano-tip based diode

Abhishek Kumar Singh and Jitendra Kumar

J. Appl. Phys. 113, 053303 (2013); http://dx.doi.org/10.1063/1.4790323 (4 pages)

Online Publication Date: 5 February 2013

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Copper nano-tip based diode structure with a gap of ∼120 nm has been fabricated by milling of a thin metallic film with a 30 kV focused gallium ion beam at a current of 100 pA. Its current-voltage characteristics measured at a pressure of ∼10−6 mbar is shown to follow the Fowler-Nordheim (F-N) field emission tunneling above ∼40 V. A simple method has been proposed to evaluate parameters like effective area (Aeff), apparent work function (ϕ), and field enhancement factor (β) of the nano-emitter. The extremely small Aeff, substantial lowering of ϕ, and high β value observed have been explained in terms of changes occurring at the emitter tip with increasing applied field. The formation of metallic nanoparticles over the substrate by local evaporation of cathode material at high currents is also demonstrated.
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79.70.+q Field emission, ionization, evaporation, and desorption
81.16.-c Methods of micro- and nanofabrication and processing
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Gk Tunneling
73.63.Bd Nanocrystalline materials

Thermochemical nonequilibrium modeling of a low-power argon arcjet wind tunnel

Hiroshi Katsurayama and Takashi Abe

J. Appl. Phys. 113, 053304 (2013); http://dx.doi.org/10.1063/1.4776765 (18 pages)

Online Publication Date: 7 February 2013

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Non-transferred low-power arcjet wind tunnels with pure argon working gas are widely used as inexpensive laboratory plasma sources to simulate a weakly ionized supersonic flow around an atmospheric entry vehicle. Many experiments using argon arcjet wind tunnels have been conducted, but their numerical modeling is not yet complete. We develop an axisymmetric Navier-Stokes model with thermochemical nonequilibrium and arc discharge that simulates the entire flow field in a steady-operating argon arcjet wind tunnel, which consists of the inside of the arcjet and its arc plume entering a rarefied vacuum chamber. The computational method we develop makes it possible to reproduce the arc column behavior far from thermochemical equilibrium in the low-voltage discharge mode typical of argon arcjets. Furthermore, the results reveal that the plasma characteristic of being far from thermal equilibrium, which is particular to argon, causes the arcjet to operate in the low-voltage mode and its arc plume to be completely thermochemically frozen. Moreover, the arc plume has electroconductive non-uniformity with an electrically insulating boundary in the radial direction. Our computed values for the shock standoff distance in front of a blunt body and the drag exerted on it agree with measured values. As a result, the self-consistent computational model in this study is useful in investigating thermochemical nonequilibrium plasma flows in argon arcjet wind tunnels.
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47.85.Gj Aerodynamics
52.30.-q Plasma dynamics and flow
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
47.10.ad Navier-Stokes equations
47.20.-k Flow instabilities
47.40.Ki Supersonic and hypersonic flows

Electrochemical hydrogen property improved in nano-structured perovskite oxide LaFeO3 for Ni/MH battery

Qiang Wang, Gang Deng, Zhiqian Chen, Yungui Chen, and Nanpu Cheng

J. Appl. Phys. 113, 053305 (2013); http://dx.doi.org/10.1063/1.4790488 (5 pages)

Online Publication Date: 7 February 2013

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Perovskite oxide LaFeO3, as a novel candidate for the electrode of Ni/MH battery, holds high specific capacity and good cyclical durability at elevated temperatures. However, the poor electrochemical kinetics is a bottleneck for the application of this type of material. By use of nano-structured materials, there are greatly enhanced values of exchange current density I0 and hydrogen diffusion coefficient D, which resulted in an improvement of electrochemical kinetics, a much higher specific capacity and excellent stability during cycling for nano-structured LaFeO3. In theory, there is a significant possibility of further advancing the hydrogen reaction kinetics of perovskite type oxides for Ni/MH battery.
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82.80.Fk Electrochemical methods
61.46.-w Structure of nanoscale materials
66.30.-h Diffusion in solids
81.16.-c Methods of micro- and nanofabrication and processing
82.45.Fk Electrodes
back to top Structural, Mechanical, Thermodynamic, and Optical Properties of Condensed Matter

Ab initio atomistic thermodynamics calculations of the initial deposition of epitaxial MgO film on GaAs(001)-β2(2 × 4)

Rizcky Tamarany, Hyung-Jun Kim, Jung-Hae Choi, and Seung-Cheol Lee

J. Appl. Phys. 113, 053501 (2013); http://dx.doi.org/10.1063/1.4789952 (5 pages)

Online Publication Date: 1 February 2013

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Ab initio calculations were performed to investigate the initial deposition of epitaxial MgO on GaAs(001)-β2(2 × 4). The differences between the chemical bonding of Mg-As and O-As were characterized by the adsorption energies of atomic O and Mg at several symmetrically distinct sites, and O bonding was substantially stronger than that of Mg. Thermodynamics were analyzed through the introduction of environmental chemical potentials simulating in situ growth conditions by the sputtering of a stoichiometric MgO target. A surface phase diagram was generated under Mg and O environments with constrained equilibrium, and the results explained the initial formation of an epitaxial MgO phase on GaAs(001)-β2(2 × 4).
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81.15.Cd Deposition by sputtering
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.30.Dz Phase diagrams of other materials
82.60.-s Chemical thermodynamics
65.40.G- Other thermodynamical quantities
68.55.aj Insulators

Magnetic and electrical/thermal transport properties of Mn-doped Mn+1AXn phase compounds Cr2−xMnxGaC (0 ≤ x ≤ 1)

S. Lin, P. Tong, B. S. Wang, Y. N. Huang, W. J. Lu, D. F. Shao, B. C. Zhao, W. H. Song, and Y. P. Sun

J. Appl. Phys. 113, 053502 (2013); http://dx.doi.org/10.1063/1.4789954 (6 pages)

Online Publication Date: 1 February 2013

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In this paper, we report the effects of partial substitution of Mn for Cr on the structural, magnetic, and electrical/thermal transport properties of Mn+1AXn phase compounds Cr2−xMnxGaC (0 ≤ x ≤ 1). As a result, the unit cell volume and the thermal conductivity decrease while the resistivity increases with increasing x. Interestingly, the magnetism of Cr2−xMnxGaC changes from the nonmagnetic Cr2GaC (x = 0) to the ferrimagnetic CrMnGaC (x = 1). In order to shed light on the discrepancy observed between Hall coefficient and Seebeck coefficient of Cr2GaC, the electrical conductivity, Hall coefficient, and magnetoresistance are analyzed within a two-band model. Furthermore, an upturn is observed in low-temperature specific heat of Cr2−xMnxGaC, which may be related with the magnetic Mn dopant.
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72.20.My Galvanomagnetic and other magnetotransport effects
72.20.Pa Thermoelectric and thermomagnetic effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Gg Ferrimagnetics
66.70.Lm Other systems such as ionic crystals, molecular crystals, nanotubes, etc.
61.66.Fn Inorganic compounds

Thermal conductivity of 4H-SiC single crystals

Rusheng Wei, Sheng Song, Kun Yang, Yingxin Cui, Yan Peng, Xiufang Chen, Xiaobo Hu, and Xiangang Xu

J. Appl. Phys. 113, 053503 (2013); http://dx.doi.org/10.1063/1.4790134 (4 pages)

Online Publication Date: 4 February 2013

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Thermal diffusivity and specific heat of 4H-SiC crystals as a function of temperature are measured, respectively, from room temperature to 600 °C. The thermal conductivity normal to c-axis was calculated from the measured data for both N-type and V-doped semi-insulating (SI) 4H-SiC single crystals. The thermal conductivity of N-type sample normal to c axis is proportional to T−1.26. It is approximately 280 W/mK at the room temperature. For V-doped SI sample, the thermal conductivity is proportional to T−1.256 and it is about 347 W/mK at room temperature, bigger than that of N-type sample. For semiconductor materials, total thermal conductivity is the sum of the contributions of lattice and carrier thermal conductivities. Temperature dependent Raman spectrum showed that the life time of phonons for N-type sample is shorter than that for SI sample. Accordingly thermal conductivity contributions from both lattice and carrier components are relatively small for N-type sample.
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66.70.Df Metals, alloys, and semiconductors
63.20.-e Phonons in crystal lattices
65.40.Ba Heat capacity
66.30.Xj Thermal diffusivity
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.30.Hv Other nonmetallic inorganics

Non-equilibrium critical point in Be-doped low-temperature-grown GaAs

Mohd Ambri Mohamed, Pham Tien Lam, and N. Otsuka

J. Appl. Phys. 113, 053504 (2013); http://dx.doi.org/10.1063/1.4790313 (7 pages)

Online Publication Date: 4 February 2013

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We studied the transition process of antisite arsenic defects in Be-doped low-temperature-grown GaAs layers by measuring the magnetization. This material exhibits bistability at non-equilibrium; at a fixed temperature in a fixed magnetic field a sample relaxes towards two different states, depending on the preceding cooling process. We observed anomalously large magnetization fluctuations in macroscopic samples during the transition from bistability to monostability with gradual change of the temperature. Slowing down of the relaxation of the magnetization is observed as a sample approaches the transition into monostability. Large fluctuations observed from a two-piece sample exhibit intermittent bursts by high-pass filtering and follow a generalized Gumbel probability density distribution. These observations suggest a possibility of the occurrence of a non-equilibrium critical point in this material. Microscopic processes underlying the observed phenomena are discussed with results of first-principles calculations of strain fields.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.72.J- Point defects and defect clusters
61.72.uj III-V and II-VI semiconductors
64.60.F- Equilibrium properties near critical points, critical exponents

Carrier dynamics and photoluminescence quenching mechanism of strained InGaSb/AlGaSb quantum wells

Nahid A. Jahan, Claus Hermannstädter, Hirotaka Sasakura, Thomas J. Rotter, Pankaj Ahirwar, Ganesh Balakrishnan, Hidekazu Kumano, and Ikuo Suemune

J. Appl. Phys. 113, 053505 (2013); http://dx.doi.org/10.1063/1.4789374 (7 pages)

Online Publication Date: 5 February 2013

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GaSb based quantum wells (QWs) show promising optical properties in near-infrared spectral range. In this paper, we present photoluminescence (PL) spectroscopies of InxGa1−xSb/AlyGa1−ySb QWs and discuss the possible thermal quenching and non-radiative carrier recombination mechanisms of the QW structures. The In and Al concentrations as well as the QW thicknesses were precisely determined with the X-ray diffraction measurements. Temperature dependent time-integrated and time-resolved PL spectroscopies resulted in the thermal activation energies of ∼45 meV, and the overall self-consistent calculation of the band parameters based on the measured physical values confirmed that the activation energies are due to the hole escape from the QW to the barriers. The relation of the present single carrier escape mechanism with the other escape mechanisms reported with other material systems was discussed based on the estimated band offset. The relation of the present thermal hole escape to the Auger recombination was also discussed.
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78.67.De Quantum wells
78.30.Fs III-V and II-VI semiconductors
73.21.Fg Quantum wells
78.55.Cr III-V semiconductors
81.40.Gh Other heat and thermomechanical treatments
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Elastocaloric and magnetocaloric effects in Ni-Mn-Sn(Cu) shape-memory alloy

Pedro O. Castillo-Villa, Lluís Mañosa, Antoni Planes, Daniel E. Soto-Parra, J. L. Sánchez-Llamazares, H. Flores-Zúñiga, and Carlos Frontera

J. Appl. Phys. 113, 053506 (2013); http://dx.doi.org/10.1063/1.4790140 (6 pages) | Cited 1 time

Online Publication Date: 5 February 2013

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We have studied magnetocaloric and elastocaloric properties of a Ni-Mn-Sn(Cu) metamagnetic shape-memory alloy undergoing a magneto-structural transition (martensitic type) close to room temperature. Changes of entropy have been induced by isothermally applying both mechanical (uniaxial stress) and magnetic fields. These entropy changes have been, respectively, estimated from dilatometric measurements giving the length of the sample as a function of temperature at selected applied forces and magnetic fields and from magnetization measurements as a function of temperature at selected applied magnetic fields. Our results indicate that the elastocaloric effect is conventional and occurs in two steps which reflect the interplay between the martensitic and the incipient magnetic transitions. By contrast, the magnetocaloric effect is inverse and occurs in a single step that encompasses the effect arising from both transitions.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.30.Kf Martensitic transformations
81.40.Lm Deformation, plasticity, and creep
62.20.fg Shape-memory effect; yield stress; superelasticity
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

High-pressure synthesis and in-situ high pressure x-ray diffraction study of cadmium tetraphosphide

Pei Wang, Fang Peng, Li Lei, Haihua Chen, Qiming Wang, Chao Xu, Ke Liu, Xiangtian Ran, Jianghua Wang, Mingjun Tang, Wendan Wang, Jing Liu, and Duanwei He

J. Appl. Phys. 113, 053507 (2013); http://dx.doi.org/10.1063/1.4790179 (6 pages)

Online Publication Date: 5 February 2013

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Pure-phase polycrystalline cadmium tetraphosphide (CdP4) has been successfully synthesized under high pressures in a large volume cubic press, and the pressure–temperature (P-T) formation boundary of CdP4 from the Cd–P binary system has been determined. The equation of state of monoclinic CdP4 has also been evaluated by synchrotron-radiation angle-dispersive X-ray diffraction (ADXRD) under quasihydrostatic compression up to 26.4 GPa in a diamond-anvil cell. The ADXRD data yield a bulk modulus B0 = 94 ± 9 GPa with a pressure derivative B0′ = 8.0. The experimental data are discussed and compared to the results of first-principles calculations.
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81.05.Hd Other semiconductors
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli
62.50.-p High-pressure effects in solids and liquids
64.30.Jk Equations of state of nonmetals

Enhanced acousto-optic interaction in two-dimensional phoxonic crystals with a line defect

Tzy-Rong Lin, Chiang-Hsin Lin, and Jin-Chen Hsu

J. Appl. Phys. 113, 053508 (2013); http://dx.doi.org/10.1063/1.4790288 (8 pages)

Online Publication Date: 5 February 2013

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This study presents acousto-optic interaction of optical waves in a two-dimensional phoxonic crystal with a line defect. Because of dual photonic and phononic band gaps generated in the phoxonic crystal, optical waves and acoustic modes can be guided and amplified, respectively, along the line defect that serves simultaneously as an optical waveguide and acoustic wave cavity. By means of finite-element analysis, we show that the confinement of the optical waves and acoustic modes in the same region of space (i.e., in the defect) leads to enhanced modulation of the optical waves by an acoustic cavity mode, and obvious shifts in eigenfrequencies and transmission peaks are observed. Stronger acousto-optic interaction is caused by the amplified acoustic fields and by the long-lifetime interaction of photons and phonons in the line defect.
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78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
42.79.Gn Optical waveguides and couplers
43.20.-f General linear acoustics
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Lamb wave band gaps in a double-sided phononic plate

Peng Wang, Tian-Ning Chen, Kun-Peng Yu, and Xiao-Peng Wang

J. Appl. Phys. 113, 053509 (2013); http://dx.doi.org/10.1063/1.4790301 (6 pages)

Online Publication Date: 5 February 2013

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In this paper, we report on the theoretical investigation of the propagation characteristics of Lamb wave in a phononic crystal structure constituted by a square array of cylindrical stubs deposited on both sides of a thin homogeneous plate. The dispersion relations, the power transmission spectra, and the displacement fields of the eigenmodes are studied by using the finite-element method. We investigate the evolution of band gaps in the double-sided phononic plate with stub height on both sides arranged from an asymmetrical distribution to a symmetrical distribution gradually. Numerical results show that as the double stubs in a unit cell arranged more symmetrically on both sides, band width shifts, new band gaps appear, and the bands become flat due to localized resonant modes which couple with plate modes. Specially, more band gaps and flat bands can be found in the symmetrical system as a result of local resonances of the stubs which interact in a stronger way with the plate modes. Moreover, the symmetrical double-sided plate exhibits lower and smaller band gap than that of the asymmetrical plate. These propagation properties of elastic or acoustic waves in the double-sided plate can potentially be utilized to generate filters, slow the group velocity, low-frequency sound insulation, and design acoustic sensors.
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63.20.D- Phonon states and bands, normal modes, and phonon dispersion
62.65.+k Acoustical properties of solids
63.20.Pw Localized modes
68.35.Iv Acoustical properties
71.20.-b Electron density of states and band structure of crystalline solids

Bulk modulus and structural changes of carbon nitride C2N2(CH2) under pressure: The strength of C–N single bond

Masaya Sougawa, Kenichi Takarabe, Yoshihisa Mori, Taku Okada, Takehiko Yagi, Hiroaki Kariyazaki, and Koji Sueoka

J. Appl. Phys. 113, 053510 (2013); http://dx.doi.org/10.1063/1.4789020 (5 pages)

Online Publication Date: 5 February 2013

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The experimental bulk modulus, B0, of C2N2(CH2) is determined to be 258 ± 3.4 GPa from the analysis of high-pressure (up to 30 GPa) X-ray diffraction patterns obtained using synchrotron radiation. This bulk modulus is 40% lower than that of diamond. At the level of a combined analysis of lattice constants determined experimentally and atomic positions obtained theoretically for the compression behavior of C2N2(CH2), the strength of the C–N single bond is determined to be the same as the C–C single bond in diamond. In other words, the tetrahedral frame of C2N2(CH2) which consists of CN3Cb, where Cb is a bridging carbon, is as hard as diamond. To account for the differing bulk moduli, we infer that the lower bulk modulus in C2N2(CH2) is due to the rotational freedom in the crystal at high pressures.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli
62.50.Ef Shock wave effects in solids and liquids
64.70.K- Solid-solid transitions
61.66.Hq Organic compounds

Lattice and grain-boundary diffusions of boron atoms in BaSi2 epitaxial films on Si(111)

K. Nakamura, M. Baba, M. Ajmal Khan, W. Du, M. Sasase, K. O. Hara, N. Usami, K. Toko, and T. Suemasu

J. Appl. Phys. 113, 053511 (2013); http://dx.doi.org/10.1063/1.4790597 (4 pages)

Online Publication Date: 6 February 2013

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A 180-nm-thick boron (B) layer was deposited on a 300-nm-thick a-axis-oriented BaSi2 epitaxial film grown by molecular beam epitaxy on Si(111) and was annealed at different temperatures in ultrahigh vacuum. The depth profiles of B were investigated using secondary ion mass spectrometry (SIMS) with O2+, and the diffusion coefficients of B were evaluated. The B profiles were reproduced well by taking both the lattice and the grain boundary (GB) diffusions into consideration. The cross-sectional transmission electron microscopy (TEM) image revealed that the GBs of the BaSi2 film were very sharp and normal to the sample surface. The plan-view TEM image exhibited that the grain size of the BaSi2 film was approximately 0.6 μm. The temperature dependence of lattice and GB diffusion coefficients was derived from the SIMS profiles, and their activation energies were found to be 4.6 eV and 4.4 eV, respectively.
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61.72.Mm Grain and twin boundaries
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.40.Gh Other heat and thermomechanical treatments
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
68.55.A- Nucleation and growth

Influence of the embedding matrix on optical properties of Ge nanocrystals-based nanocomposite

S. Parola, E. Quesnel, V. Muffato, J. Bartringer, and A. Slaoui

J. Appl. Phys. 113, 053512 (2013); http://dx.doi.org/10.1063/1.4789959 (8 pages)

Online Publication Date: 6 February 2013

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Germanium nanocrystals were prepared by a nanocluster source and characterized by photoluminescence and spectroscopic photometry methods. The optical measurements were carried out in order to estimate the effective bandgap of the Ge nanocrystals. Both Mie theory and the quantum confinement theory were applied to interpret the extracted absorption data. We found that the quantum confinement theory enables to explain the nanocrystal size and the host matrix dependence of the nanocrystal bandgap. On the other hand, the photoluminescence measurements have not allowed to confirm the bandgap evaluated from absorption data. This is explained as due to the dominant effect of the recombination at the nanocrystals surface.
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78.55.Ap Elemental semiconductors
81.16.-c Methods of micro- and nanofabrication and processing
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
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