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3 Jan 2011

Volume 98, Issue 1, Articles (01xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 98, 011901 (2011); http://dx.doi.org/10.1063/1.3532961 (3 pages)

Emanuele Pontecorvo, Michele Ortolani, Dario Polli, Marco Ferretti, Giancarlo Ruocco, Giulio Cerullo, and Tullio Scopigno
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Editorial

Nghi Q. Lam, Editor

Appl. Phys. Lett. 98, 010401 (2011); http://dx.doi.org/10.1063/1.3533024 (1 page)

Online Publication Date: 3 January 2011

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01.30.-y Physics literature and publications
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Vertical cavity surface emitting laser action of an all monolithic ZnO-based microcavity

S. Kalusniak, S. Sadofev, S. Halm, and F. Henneberger

Appl. Phys. Lett. 98, 011101 (2011); http://dx.doi.org/10.1063/1.3533800 (3 pages) | Cited 2 times

Online Publication Date: 3 January 2011

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We report on room temperature laser action of an all monolithic ZnO-based vertical cavity surface emitting laser (VCSEL) under optical pumping. The VCSEL structure consists of a 2λ microcavity containing eight ZnO/Zn0.92Mg0.08O quantum wells embedded in epitaxially grown Zn0.92Mg0.08O/Zn0.65Mg0.35O distributed Bragg reflectors (DBRs). As a prerequisite, design and growth of high reflectivity DBRs based on ZnO and (Zn,Mg)O for optical devices operating in the ultraviolet and blue-green spectral ranges are discussed.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Excitation of Eu3+ in gallium nitride epitaxial layers: Majority versus trap defect center

N. Woodward, J. Poplawsky, B. Mitchell, A. Nishikawa, Y. Fujiwara, and V. Dierolf

Appl. Phys. Lett. 98, 011102 (2011); http://dx.doi.org/10.1063/1.3533806 (3 pages) | Cited 4 times

Online Publication Date: 3 January 2011

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We report studies of the excitation mechanism of Eu ions in situ doped during organometallic vapor-phase epitaxy (OMVPE) of GaN. We find that the bright red emission under above-band gap excitation originates primarily from an incorporation site that exhibits high excitation efficiency but occurs in low relative abundance (<3%). The latter represents a device efficiency bottleneck, limiting the emission at high excitation intensities. The majority site, which scales well with the total Eu concentration, exhibits low energy transfer efficiency but dominates the emission under direct excitation in the visible spectral region due to high relative abundance (>97%).
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78.66.Fd III-V semiconductors
61.72.uj III-V and II-VI semiconductors
81.05.Ea III-V semiconductors
78.40.Fy Semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.ag Semiconductors

Characteristics of a high speed 1.22 μm tunnel injection p-doped quantum dot excited state laser

Chi-Sen Lee, Pallab Bhattacharya, Thomas Frost, and Wei Guo

Appl. Phys. Lett. 98, 011103 (2011); http://dx.doi.org/10.1063/1.3535607 (3 pages) | Cited 1 time

Online Publication Date: 4 January 2011

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The measured characteristics of excited state lasing in tunnel injection p-doped InAs quantum dot lasers are reported. Excited state lasing at 1.22 μm is ensured by a high-reflectivity facet coating which is designed to suppress ground state lasing in the devices. The saturation modal gain in the excited states is 56 cm−1, which is a factor of ∼ 2.5 higher than that of the ground state. The small-signal modulation bandwidth for I = 4.5Ith is 13.5 GHz and the differential gain is 1.1×10−15 cm2.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.By Design of specific laser systems

Macroporous photonic crystal-based vapor detectors created by doctor blade coating

Hongta Yang and Peng Jiang

Appl. Phys. Lett. 98, 011104 (2011); http://dx.doi.org/10.1063/1.3535977 (3 pages) | Cited 2 times

Online Publication Date: 4 January 2011

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We report the achievement of rapid and reversible vapor detection by using 3D macroporous photonic crystals created by a continuous and scalable bottom-up technology. Capillary condensation of a condensable vapor in the interconnected macropores with ∼ 74% porosity leads to the increase of the effective refractive index of the diffractive medium, resulting in the redshift of the optical stop bands. The wavelength shift is linearly proportional to the vapor partial pressure for a spectrum of vapors. Optical simulation and theoretical prediction based on Kelvin equation suggest that a liquid film is formed on the walls of the macropores during vapor condensation.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Photonic crystal slab quantum well infrared photodetector

S. Kalchmair, H. Detz, G. D. Cole, A. M. Andrews, P. Klang, M. Nobile, R. Gansch, C. Ostermaier, W. Schrenk, and G. Strasser

Appl. Phys. Lett. 98, 011105 (2011); http://dx.doi.org/10.1063/1.3537954 (3 pages)

Online Publication Date: 4 January 2011

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In this letter we present a quantum well infrared photodetector (QWIP), which is fabricated as a photonic crystal slab (PCS). With the PCS it is possible to enhance the absorption efficiency by increasing photon lifetime in the detector active region. To understand the optical properties of the device we simulate the PCS photonic band structure, which differs significantly from a real two-dimensional photonic crystal. By fabricating a PCS-QWIP with 100x less quantum well doping, compared to a standard QWIP, we are able to see strong absorption enhancement and sharp resonance peaks up to temperatures of 170 K.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials

Angular constraint on light-trapping absorption enhancement in solar cells

Zongfu Yu and Shanhui Fan

Appl. Phys. Lett. 98, 011106 (2011); http://dx.doi.org/10.1063/1.3532099 (3 pages)

Online Publication Date: 4 January 2011

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Light trapping for solar cells can reduce production cost and improve energy conversion efficiency. Understanding some of the basic theoretical constraints on light trapping is therefore of fundamental importance. Here, we develop a general angular constraint on the absorption enhancement in light trapping. We show that there is an upper limit for the angular integration of absorption enhancement factors. This limit is determined by the number of accessible resonances supported by an absorber.
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88.40.hj Efficiency and performance of solar cells
88.40.hm Cost of production of solar cells

Gain dynamics of an InAs/InGaAsP quantum dot semiconductor optical amplifier operating at 1.5 μm

J. Park, N. J. Kim, Y. D. Jang, E. G. Lee, J. M. Lee, J. S. Baek, J. H. Kim, H. S. Lee, K. J. Yee, D. Lee, S. H. Pyun, W. G. Jeong, and J. Kim

Appl. Phys. Lett. 98, 011107 (2011); http://dx.doi.org/10.1063/1.3533365 (3 pages)

Online Publication Date: 5 January 2011

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The gain and phase dynamics of a high quality quantum dot semiconductor optical amplifier were measured at various wavelengths. In the ground state (GS), the amplitude of the slow component was negligible and the fast dominant gain recovery time was 0.7 ps. In the excited state (ES), the slow component was not negligible although small. The time required to recover from 90% to 10% was 2.0 ps in the GS but gradually increased to 31 ps in the ES. This finding predicts no pattern effects in the GS, but finite pattern effects in the ES.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
81.07.Ta Quantum dots
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
81.05.Ea III-V semiconductors

Influence of threading dislocations on GaN-based metal-semiconductor-metal ultraviolet photodetectors

Dabing Li, Xiaojuan Sun, Hang Song, Zhiming Li, Yiren Chen, Guoqing Miao, and Hong Jiang

Appl. Phys. Lett. 98, 011108 (2011); http://dx.doi.org/10.1063/1.3536480 (3 pages) | Cited 3 times

Online Publication Date: 5 January 2011

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The influence of threading dislocations on the properties of GaN-based metal-semiconductor-metal (MSM) ultraviolet photodetectors was investigated. It was found that screw dislocations had a strong influence on the dark current of the photodetectors, while edge dislocations had the predominant effect on their responsivity. The dark current increased as the screw dislocation density increased due to their lowering of the Schottky barrier height. However, the responsivity of the photodetectors decreased with increasing edge dislocation density because of the dangling bonds along those edge dislocation lines which enhance the recombination of photogenerated electron-hole pairs. The results suggest that reducing both the screw and edge dislocation densities is an effective way to improve the photoelectric property of GaN-based MSM ultraviolet photodetectors.
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85.60.Gz Photodetectors (including infrared and CCD detectors)

Surface-plasmon-induced light absorption on a rough silver surface

Sun-Kyung Kim, Ho-Seok Ee, Woonkyung Choi, Soon-Hong Kwon, Ju-Hyung Kang, Yoon-Ho Kim, Hoki Kwon, and Hong-Gyu Park

Appl. Phys. Lett. 98, 011109 (2011); http://dx.doi.org/10.1063/1.3537812 (3 pages) | Cited 4 times

Online Publication Date: 5 January 2011

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We investigate light absorption in metal films, silver and aluminum, with different surface roughness. Measurements using an integrating sphere show that the reflectance in silver decreases significantly with increasing surface roughness whereas the reflectance in aluminum is almost constant. The experimental results agree well with numerical simulations in which the surface roughness of metal is described properly. In particular, the simulations demonstrate that the absorption by surface-plasmon-polaritons excited on a rough silver surface causes the surface-dependent reflectance in silver. This study suggests a convenient and feasible rule to rationally design a backside metal reflector toward high-efficiency light-emitting diodes and photovoltaics.
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78.68.+m Optical properties of surfaces
78.66.Bz Metals and metallic alloys
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Polarized spontaneous emission from blue-green m-plane GaN-based light emitting diodes

Stuart E. Brinkley, You-Da Lin, Arpan Chakraborty, Nathan Pfaff, Daniel Cohen, James S. Speck, Shuji Nakamura, and Steven P. DenBaars

Appl. Phys. Lett. 98, 011110 (2011); http://dx.doi.org/10.1063/1.3541655 (3 pages) | Cited 5 times

Online Publication Date: 5 January 2011

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The polarization of spontaneous emission was investigated for various indium compositions and quantum wells on m-plane oriented gallium nitride (GaN) light emitting diodes (LEDs) grown on bulk-GaN substrates. Internal light scattering and depolarization was mitigated with application of absorber materials to the LED die. The polarization ratio (ρ) was measured under electrical injection for devices with InGaN active regions emitting up to 520 nm and observed as high as 96%. Values of ρ were independent of drive current. The valence band energy separation (ΔE) was characterized using spectral measurement and temperature dependent optical analysis of valence band hole distributions.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.67.De Quantum wells
73.21.Fg Quantum wells
71.20.Nr Semiconductor compounds

Strong enhancement of direct transition photoluminescence with highly tensile-strained Ge grown by molecular beam epitaxy

Yijie Huo, Hai Lin, Robert Chen, Maria Makarova, Yiwen Rong, Mingyang Li, Theodore I. Kamins, Jelena Vuckovic, and James S. Harris

Appl. Phys. Lett. 98, 011111 (2011); http://dx.doi.org/10.1063/1.3534785 (3 pages) | Cited 10 times

Online Publication Date: 6 January 2011

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Highly tensile-strained layers of Ge were grown via molecular beam epitaxy using step-graded InxGa1−xAs buffer layers on (100) GaAs. These layers have biaxial tensile-strain of up to 2.33%, have surface roughness of <1.1 nm, and are of high quality as seen with transmission electron microscopy. Low-temperature photoluminescence (PL) suggests the existence of direct-bandgap Ge when the strain is greater than 1.7%, and we see a greater than 100× increase in the PL intensity of the direct transition with 2.33% tensile-strain over the unstrained case. These results show promise for the use of tensile-strained Ge in optoelectronics monolithically integrated on Si.
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78.66.Db Elemental semiconductors and insulators
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.60.-p Physical properties of thin films, nonelectronic
78.55.Ap Elemental semiconductors
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Real-time probing of ultrafast residual charge dynamics

Junjie Li, Xuan Wang, Zhaoyang Chen, Jun Zhou, Samuel S. Mao, and Jianming Cao

Appl. Phys. Lett. 98, 011501 (2011); http://dx.doi.org/10.1063/1.3533811 (3 pages) | Cited 3 times

Online Publication Date: 6 January 2011

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The temporal evolution of residual charges during laser ablation of metal and dielectric materials was investigated by measuring the correlated transient electric field using femtosecond electron shadow imaging and deflectometry. The results indicate that residual charges in metals can redistribute themselves almost instantly, abiding by the boundary conditions and Maxwell equations in the same way as they would at electrostatic equilibrium condition, but residual charges in dielectrics are confined within the excited area for hundreds of picoseconds and beyond. These observations provide an experimental support to the alleged Coulomb explosion phenomenon in previous studies as well as a reference for modeling residual charge dynamics.
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78.47.J- Ultrafast spectroscopy (<1 psec)
52.38.Mf Laser ablation
79.20.Eb Laser ablation

On the quenching of excited electronic states of molecular nitrogen in nanosecond pulsed discharges in atmospheric pressure air

M. S. Bak, W. Kim, and M. A. Cappelli

Appl. Phys. Lett. 98, 011502 (2011); http://dx.doi.org/10.1063/1.3535986 (3 pages) | Cited 2 times

Online Publication Date: 7 January 2011

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Emission measurements are carried out to study the quenching of excited electronic states of nitrogen, N2∗, in nanosecond pulsed discharges in atmospheric pressure air and nitrogen. The results reveal that ground state N2 quenches N2(C) and N2(B) at rates less than dissociative quenching by ground state O2 by a factor of 4 and 2.5, respectively. Kinetic simulations with the inferred quench rates indicate that the dissociative quenching of N2∗ by O2 is responsible for 82% of atomic oxygen production while electron-impact dissociation of O2 is for 5% under these discharge conditions.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
34.80.Ht Dissociation and dissociative attachment
52.80.-s Electric discharges
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
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Visualizing coherent phonon propagation in the 100 GHz range: A broadband picosecond acoustics approach

Emanuele Pontecorvo, Michele Ortolani, Dario Polli, Marco Ferretti, Giancarlo Ruocco, Giulio Cerullo, and Tullio Scopigno

Appl. Phys. Lett. 98, 011901 (2011); http://dx.doi.org/10.1063/1.3532961 (3 pages) | Cited 8 times

Online Publication Date: 3 January 2011

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Building on a 1 kHz amplified Ti:sapphire laser source, we developed a novel pump-probe setup for broadband picosecond acoustics using a white-light continuum probe coupled to an optical multichannel analyzer. The system allows one to access, in a single measurement, acoustic parameters such as sound velocity and attenuation all over the bandwidth of the acoustic wave-packet launched by the pump pulse. We use the setup to measure the sound attenuation in fused silica and observe a dynamic crossover occurring at ≈170 GHz.
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43.58.Dj Sound velocity
63.20.-e Phonons in crystal lattices
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
62.65.+k Acoustical properties of solids

Temperature contour maps at the strain-induced martensitic transition of a Cu–Zn–Al shape-memory single crystal

Eduard Vives, Susan Burrows, Rachel S. Edwards, Steve Dixon, Lluís Mañosa, Antoni Planes, and Ricardo Romero

Appl. Phys. Lett. 98, 011902 (2011); http://dx.doi.org/10.1063/1.3533403 (3 pages)

Online Publication Date: 3 January 2011

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We study temperature changes at the reverse strain-induced martensitic transformation in a Cu–Zn–Al single crystal. Infrared thermal imaging reveals a markedly inhomogeneous temperature distribution. The evolution of the contour temperature maps enables information to be extracted on the kinetics of the interface motion.
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81.30.Kf Martensitic transformations
64.70.K- Solid-solid transitions
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder

Tunability of third order nonlinear absorption in (Pb,La)(Zr,Ti)O3 thin films

D. Ambika, Viswanathan Kumar, C. S. Suchand Sandeep, and Reji Philip

Appl. Phys. Lett. 98, 011903 (2011); http://dx.doi.org/10.1063/1.3534786 (3 pages) | Cited 1 time

Online Publication Date: 3 January 2011

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This paper reports the demonstration of the tunability of the third order nonlinear optical absorption in (Pb1−3x/2Lax)(Zr0.53Ti0.47) (PLZT) thin films. The optical nonlinearity is investigated employing the open aperture z-scan technique at the off-resonant wavelength of 532 nm. By altering the defect chemistry in PZT through A-site aliovalent lanthanum substitution, the nonlinear optical (NLO) absorption can be effectively tuned. The results of the influence of lanthanum concentration on leakage current and microstructure have also been combined to confirm the defect-mediated mechanism of NLO absorption in PLZT thin films.
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42.79.Wc Optical coatings
78.66.Nk Insulators
42.65.-k Nonlinear optics

Ultrasmooth growth of amorphous silicon films through ion-induced long-range surface correlations

A. Redondo-Cubero, R. Gago, and L. Vázquez

Appl. Phys. Lett. 98, 011904 (2011); http://dx.doi.org/10.1063/1.3535612 (3 pages)

Online Publication Date: 4 January 2011

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Ultrasmooth amorphous silicon films with a constant roughness below 0.2 nm were produced for film thickness up to ∼ 1 μm by magnetron sputtering under negative voltage substrate biasing (100–400 V). In contrast, under unbiased conditions the roughness of the resulting mounded films increased linearly with growth time due to shadowing effects. A detailed analysis of the amorphous film growth dynamics proves that the bias-induced ultrasmoothness is produced by a downhill mass transport process that leads to an extreme surface leveling inducing surface height correlations up to lateral distances close to 0.5 μm.
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81.05.Cy Elemental semiconductors
68.55.ag Semiconductors
81.15.Cd Deposition by sputtering
68.35.bj Amorphous semiconductors, glasses

Structure and characteristics of ultrathin indium tin oxide films

Er-Jia Guo, Haizhong Guo, Huibin Lu, Kuijuan Jin, Meng He, and Guozhen Yang

Appl. Phys. Lett. 98, 011905 (2011); http://dx.doi.org/10.1063/1.3536531 (3 pages) | Cited 3 times

Online Publication Date: 4 January 2011

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A series of indium tin oxide (ITO) thin-films with various thicknesses from 2 to 200 monolayers (ML) have been epitaxially grown on LaAlO3 substrates by laser molecular-beam epitaxy. The measurements of x-ray diffraction, atomic force microscopy, four-probe method, and optical transmittance reveal that the film thickness strongly affects the structural, electrical, and optical properties of ITO thin-films, and the ITO thin-films exist at a critical thickness of metal-insulator transition at about 4–5 ML. The electrical transport property has been discussed with the different conductive models.
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68.55.-a Thin film structure and morphology
73.61.Le Other inorganic semiconductors
78.66.Li Other semiconductors
71.20.Nr Semiconductor compounds
71.30.+h Metal-insulator transitions and other electronic transitions
68.37.Ps Atomic force microscopy (AFM)

Tunable helical ribbons

Z. Chen, C. Majidi, D. J. Srolovitz, and M. Haataja

Appl. Phys. Lett. 98, 011906 (2011); http://dx.doi.org/10.1063/1.3530441 (3 pages) | Cited 5 times

Online Publication Date: 5 January 2011

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The helix angle, chirality, and radius of helical ribbons are predicted with a comprehensive, three-dimensional analysis that incorporates elasticity, differential geometry, and variational principles. In many biological and engineered systems, ribbon helicity is commonplace and may be driven by surface stress, residual strain, and geometric or elastic mismatch between layers of a laminated composite. Unless coincident with the principle geometric axes of the ribbon, these anisotropies will lead to spontaneous, three-dimensional helical deformations. Analytical, closed-form ribbon shape predictions are validated with table-top experiments. More generally, our approach can be applied to develop materials and systems with tunable helical geometries.
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46.25.-y Static elasticity
62.20.D- Elasticity
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
81.40.Jj Elasticity and anelasticity, stress-strain relations
46.35.+z Viscoelasticity, plasticity, viscoplasticity

Efficient fluorescence emission and photon conversion of LaOF:Eu3+ nanocrystals

Dangli Gao, Hairong Zheng, Xiangyu Zhang, Zhenxing Fu, Zhenglong Zhang, Yu Tian, and Min Cui

Appl. Phys. Lett. 98, 011907 (2011); http://dx.doi.org/10.1063/1.3535983 (3 pages) | Cited 1 time

Online Publication Date: 5 January 2011

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Efficient spectral conversion of 325–550 nm light to 570–710 nm light has been demonstrated in LaOF:Eu3+ nanocrystals. When levels above the 5D0 level of Eu3+ are optically excited, strong emission arising from the 5D0 level is obtained in the range of 570–710 nm, a highly efficient working range for organic solar cells. The influences of ambient temperature, particle size, dopant concentration, and codoped ions on the fluorescence intensity of Eu3+ are discussed in detail. The photon conversion efficiency can reach 3.91% in LaOF:Eu3+ codoped with Tm3+, if light reflection and scattering effects are ignored
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78.66.Nk Insulators
78.55.Hx Other solid inorganic materials
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Electroluminescence and capacitance-voltage characteristics of single-crystal n-type AlN (0001)/p-type diamond (111) heterojunction diodes

Kazuyuki Hirama, Yoshitaka Taniyasu, and Makoto Kasu

Appl. Phys. Lett. 98, 011908 (2011); http://dx.doi.org/10.1063/1.3533380 (3 pages) | Cited 3 times

Online Publication Date: 5 January 2011

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n-type single-crystal AlN (0001) layers were grown on diamond (111) substrates by metalorganic vapor phase epitaxy. We observed current-injected emission at 235 nm wavelength at room temperature in an n-type AlN/p-type diamond heterojunction diode. The emission is attributed to free-exciton recombination in diamond. From capacitance-voltage measurements of the n-type AlN/p-type diamond heterojunction, we determined that the AlN/diamond heterojunction exhibits the staggered (type-II) band alignment with a conduction band offset (ΔEC) of 3.5 eV and a valence band offset (ΔEV) of 4.0 eV.
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85.30.Kk Junction diodes

Negative refraction experiments with guided shear-horizontal waves in thin phononic crystal plates

Min Kyung Lee, Pyung Sik Ma, Il Kyu Lee, Hoe Woong Kim, and Yoon Young Kim

Appl. Phys. Lett. 98, 011909 (2011); http://dx.doi.org/10.1063/1.3533641 (3 pages) | Cited 6 times

Online Publication Date: 5 January 2011

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This paper presents the experimental evidence of negative refraction of a guided ultrasonic shear-horizontal wave in a phononic crystal plate, a thin aluminum plate with periodically spaced circular holes. Unlike bulk wave experiments, guided-wave experiments allow the full measurement of negatively refracted waves propagating into a base aluminum plate from the phononic crystal plate. The present guided-wave experiments were conducted with the planar solenoid array-type orientation-adjustable patch-type magnetostrictive transducer having good beam directivity. An effective technique to estimate negative refraction angles from the experimental measurements is suggested, yielding values in good agreement with theoretically calculated angles.
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62.30.+d Mechanical and elastic waves; vibrations
63.22.Kn Clusters and nanocrystals
62.65.+k Acoustical properties of solids

Elimination of interface states of Co2MnSi/MgO/Co2MnSi magnetic tunneling junction by inserting an Al atomic layer

H. L. Yu and G. W. Yang

Appl. Phys. Lett. 98, 011910 (2011); http://dx.doi.org/10.1063/1.3540646 (3 pages) | Cited 2 times

Online Publication Date: 5 January 2011

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Aiming at improvement performance of Co2MnSi/MgO/Co2MnSi magnetic tunneling junction (MTJ), we have studied interface behaviors of Co2MnSi/MgO by inserting an Al atomic layer between Heusler alloy and barrier, i.e., CoCo/Al/O, MnSi/Al/O, MnMn/Al/O and SiSi/Al/O four interfaces. It was found that CoCo/Al/O is stable and half-metallic, meaning interface states can be eliminated in this system. Hybridization and repulsion of transition-metal d and p states of sp atoms at interface and electrons transfer between interfacial atoms were suggested to be responsible for interface states elimination. These findings open a way to eliminate the interface states in MTJ.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.65.Ac Multilayers
73.21.Ac Multilayers
72.25.Ba Spin polarized transport in metals

Fano effect of metamaterial resonance in terahertz extraordinary transmission

Xiao Xiao, Jinbo Wu, Fumiaki Miyamaru, Mengying Zhang, Shunbo Li, Mitsuo W. Takeda, Weijia Wen, and Ping Sheng

Appl. Phys. Lett. 98, 011911 (2011); http://dx.doi.org/10.1063/1.3541652 (3 pages) | Cited 2 times

Online Publication Date: 5 January 2011

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We show that the terahertz resonant transmission through metal hole array can be tailored by filling the holes with metamaterials. Experiment and finite difference time domain simulations show this type of resonant transmission to be induced by locally resonant modes, instead of the usual lateral surface grating mode. As the metamaterial’s local resonances can be manipulated by varying their geometric configurations, this type of resonant transmission can be tuned over a broad frequency regime that is subwavelength to the array periodicity, with a transmission profile that can also be tailored by the frequency location of the resonance. Such tunability of resonant transmission, with its attendant enhanced local field intensity in the vicinity of the aperture, may provide some potential applications.
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81.05.Xj Metamaterials for chiral, bianisotropic and other complex media
79.60.-i Photoemission and photoelectron spectra
78.70.Gq Microwave and radio-frequency interactions
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
42.70.-a Optical materials
63.20.Pw Localized modes
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