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18 Jun 2012

Volume 100, Issue 25, Articles (25xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 252401 (2012); http://dx.doi.org/10.1063/1.4727909 (4 pages)

Ming Yan, Christian Andreas, Attila Kákay, Felipe García-Sánchez, and Riccardo Hertel
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Nondestructive two-dimensional phase imaging of embedded defects via on-chip spintronic sensor

Z. X. Cao, M. Harder, L. Fu, B. Zhang, W. Lu, G. E. Bridges, Y. S. Gui, and C.-M. Hu

Appl. Phys. Lett. 100, 252406 (2012); http://dx.doi.org/10.1063/1.4729785 (3 pages) | Cited 2 times

Online Publication Date: 19 June 2012

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A microwave near field phase imaging technique has been achieved by an on-chip spintronic sensor. The sensor directly rectifies a microwave field into a dc voltage signal by employing the spintronic principle, in which the relative phase between microwave electric and magnetic fields plays an important role. By manipulating the relative phase, the sensor can nondestructively detect embedded defects of subwavelength size.
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81.70.-q Methods of materials testing and analysis
61.72.-y Defects and impurities in crystals; microstructure

Synthesis, structure, and magnetic behavior of nanoparticles of cubic ZnMnO3

James D. Rall, S. Thota, J. Kumar, and M. S. Seehra

Appl. Phys. Lett. 100, 252407 (2012); http://dx.doi.org/10.1063/1.4729817 (4 pages) | Cited 3 times

Online Publication Date: 19 June 2012

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Synthesis and nature of magnetism in ZnMnO3 nanoparticles with cubic spinel structure (a = 8.369 Å and size D ≃ 25 nm) are reported. Magnetization M vs. H and M vs. T data yield ferrimagnetism with TN ≃ 20 K, μ/Mn = 4.46 μB, MS ≃ 18.5 emu/g, and a transition at TS ≃ 7 K. For T < TN, coercivity and exchange-bias approach zero at TN with anomaly at TS. Using magnetic data and simulations, structure of [Zn2+][Zn1/32+Mn2/33+Mn2/34+□1/3]O11/3 with antiparallel moments of Mn4+ and Mn3+ is proposed.
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75.75.Cd Fabrication of magnetic nanostructures
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Pp Magnetic semiconductors
75.30.Cr Saturation moments and magnetic susceptibilities
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Strain, spin disorder, and thickness dependence of magneto-transport in Sm0.55Sr0.45MnO3 films

M. M. Saber, M. Egilmez, F. Schoofs, O. Ofer, M. Månsson, J. W. A. Robinson, M. Blamire, K. H. Chow, and J. Jung

Appl. Phys. Lett. 100, 252408 (2012); http://dx.doi.org/10.1063/1.4728988 (5 pages) | Cited 2 times

Online Publication Date: 20 June 2012

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The correlation between the strain, spin disorder, and the thickness dependence of the magneto-transport has been investigated in as-grown and post-annealed 25-300-nm thick films of Sm0.55Sr0.45MnO3 (SSMO) deposited on SrTiO3 (STO) and LaAlO3 (LAO) substrates. In the post-annealed SSMO/LAO films, the epitaxial strain increases with a decreasing thickness; however, it is independent of the thickness of the post-annealed SSMO/STO films. In both cases, the reduction of the metal-insulator transition temperature with a decreasing thickness was observed. This behavior is attributed to an increasing compressive strain in the SSMO/LAO films and to spin disorder effects in the SSMO/STO ones.
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72.20.My Galvanomagnetic and other magnetotransport effects
81.40.Gh Other heat and thermomechanical treatments
68.55.A- Nucleation and growth
71.30.+h Metal-insulator transitions and other electronic transitions

History dependence of directly observed magnetocaloric effects in (Mn, Fe)As

Milan Bratko, Kelly Morrison, Ariana de Campos, Sergio Gama, Lesley F. Cohen, and Karl G. Sandeman

Appl. Phys. Lett. 100, 252409 (2012); http://dx.doi.org/10.1063/1.4729893 (4 pages)

Online Publication Date: 20 June 2012

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We use a calorimetric technique operating in sweeping magnetic field to study the thermomagnetic history-dependence of the magnetocaloric effect (MCE) in Mn0.985Fe0.015As. We study the magnetization history for which a “colossal” MCE has been reported when inferred indirectly via a Maxwell relation. We observe no colossal effect in the direct calorimetric measurement. We further examine the impact of mixed-phase state on the MCE and show that the first order contribution scales linearly with the phase fraction. This validates various phase-fraction based methods developed to remove the colossal peak anomaly from Maxwell-based estimates.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.20.Pa Thermoelectric and thermomagnetic effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Ferromagnetism and manipulation of topological surface states in Bi2Se3 family by 2p light elements

Chengwang Niu, Ying Dai, Zhenkui Zhang, Yandong Ma, and Baibiao Huang

Appl. Phys. Lett. 100, 252410 (2012); http://dx.doi.org/10.1063/1.4729934 (5 pages) | Cited 2 times

Online Publication Date: 20 June 2012

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The manipulation effects by doping of 2p light elements X (X = B, C, and N) on topological surface states in V2VI3 (V = Bi and Sb, VI = Se and Te) are systemically explored. Our results unveil that X doping at anion sites can induce magnetic moments and gap opening at the Dirac point. To have a stable magnetic ground state, the dopant 2p states must be sufficiently localized, which closely depends on the X-V bond lengths. The incorporation of 2p dopants paves a promising way of tuning the properties of topological insulators and may find applications in spintronics.
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73.20.At Surface states, band structure, electron density of states
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
61.72.uf Ge and Si
71.20.Nr Semiconductor compounds

Vacancy mediated room temperature ferromagnetism in Co-doped Dy2O3

A. Bandyopadhyay, S. Sutradhar, B. J. Sarkar, A. K. Deb, and P. K. Chakrabarti

Appl. Phys. Lett. 100, 252411 (2012); http://dx.doi.org/10.1063/1.4729386 (5 pages) | Cited 1 time

Online Publication Date: 20 June 2012

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Nanoparticles of Co doped dysprosium oxide [Dy1.90Co0.10O3] were prepared by co-precipitating the precursor salts in presence of air and argon gas. Crystallographic phase and substitution of Co-ion in Dy2O3 were confirmed by Rietveld analysis of the x-ray diffraction patterns. Magnetic susceptibility and magnetization as a function of temperature and magnetic field were measured by Faraday and Superconducting quantum inteference device (SQUID) magnetometers, which showed that the sample synthesized in the inert atmosphere is ferromagnetic at room temperature. But no such effect has been observed in the other sample. This observation confirmed that vacancy mediated ferromagnetism can be introduced in the Co-doped dysprosium oxide.
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75.75.Cd Fabrication of magnetic nanostructures
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.72.jd Vacancies

Bragg resonances of magnetostatic surface spin waves in a layered structure: Magnonic crystal-dielectric-metal

E. N. Beginin, Yu. A. Filimonov, E. S. Pavlov, S. L. Vysotskii, and S. A. Nikitov

Appl. Phys. Lett. 100, 252412 (2012); http://dx.doi.org/10.1063/1.4730374 (5 pages) | Cited 2 times

Online Publication Date: 21 June 2012

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It is experimentally shown that metal cladding of the surface of a one-dimensional magnonic crystal destroys the Bragg band gaps in microwave transmission spectra of propagating magnetostatic surface spin waves in magnonic crystal. This is a consequence of violating a phase synchronism condition of forward and reflected by a magnonic crystal magnetostatic surface wave. When a magnetostatic surface wave propagates in a layered structure, ferromagnetic film with a magnonic crystal-dielectric layer-metal cladding this synchronism condition can also be fulfilled, not depending on the thickness of a dielectric layer.
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75.30.Ds Spin waves
75.70.Ak Magnetic properties of monolayers and thin films
75.70.Rf Surface magnetism
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
78.70.Gq Microwave and radio-frequency interactions
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)

Reduced spin transfer torque switching current density with non-collinear polarizer layer magnetization in magnetic multilayer systems

Chun-Yeol You

Appl. Phys. Lett. 100, 252413 (2012); http://dx.doi.org/10.1063/1.4730376 (4 pages) | Cited 2 times

Online Publication Date: 22 June 2012

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Through micromagnetic simulations, it was found that the spin transfer torque (STT) switching current density is reduced with non-collinear polarizer layer magnetization. The dependence of the switching current density on the polarizer layer magnetization angle was investigated, and a typical magnetic tunneling junction structure with an exchange biased synthetic ferrimagnetic polarizer layers was considered. The easy axis of the polarizer layer was varied through controlling the exchange bias field direction in the ellipse cross-section nano-pillar structures. It was found that the switching current density was reduced by 39% when the exchange bias field was 10° from the long axis of the ellipse without the perpendicular STT. When the effect of the perpendicular STT was included, the switching current reductions were general for the non-collinear polarizer layer.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.75.-c Magnetic properties of nanostructures
75.30.Et Exchange and superexchange interactions
75.78.Cd Micromagnetic simulations
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Exciton and carrier spin relaxations in InGaAs lattice-matched to off-cut Ge substrates

Takenori Ushimi, Hiromi Nakata, Toshihiro Ishizuka, Kazutoshi Sasayama, Shulong Lu, Jianrong Dong, and Atsushi Tackeuchi

Appl. Phys. Lett. 100, 252414 (2012); http://dx.doi.org/10.1063/1.4730386 (3 pages)

Online Publication Date: 22 June 2012

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We have investigated the exciton and carrier spin relaxations in InGaAs lattice-matched to Ge substrates. Time-resolved spin-dependent pump and probe reflectance measurements revealed a spin relaxation behavior between 10 and 300 K. The presence of the carrier density dependence of spin relaxation time at 10-200 K implies that the Bir-Aronov-Pikus process is effective. At 250-300 K, the strong temperature and weak carrier density dependences of spin relaxation time show that the D’yakonov-Perel’ process is dominant. The longest observed spin relaxation time of 2.6 ns at 77 K is explained by the decrease in the spatial overlap of electrons and holes.
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81.05.Ea III-V semiconductors
72.80.Ey III-V and II-VI semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.35.-y Excitons and related phenomena
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Electrical transport properties of (110)-oriented PrBa2(Cu0.8Ga0.2)3O7 thin films

Hom Kandel, Tar-Pin Chen, Shawn Bourdo, Milko N. Iliev, Fumiya Watanabe, Hye-Won Seo, and Tito Viswanathan

Appl. Phys. Lett. 100, 252601 (2012); http://dx.doi.org/10.1063/1.4729871 (4 pages)

Online Publication Date: 19 June 2012

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The electrical transport properties of (110)-oriented PrBa2(Cu0.8Ga0.2)3O7 (PBCGO) thin films have been investigated. The electrical resistivity, ρ(T), of (110)-oriented PBCGO thin films is 8.91 × 105 Ω-cm at 77 K, about five orders of magnitude higher than that of the (110)-oriented PrBa2Cu3O7 thin films and follows Mott’s T−1/4 law up to room temperature. Our experimental results suggest filling and localization of holes in Cu-O chains of (110)-oriented PBCGO thin films. We observed very less proximity effect on YBa2Cu3O7 (YBCO)/PBCGO multilayers indicating that the (110)-oriented PBCGO thin films may serve as effective insulators in YBCO SIS tunneling Josephson junction.
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74.25.fc Electric and thermal conductivity
74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions
74.72.-h Cuprate superconductors
74.78.Fk Multilayers, superlattices, heterostructures

Etching suspended superconducting tunnel junctions from a multilayer

H. Q. Nguyen, L. M. A. Pascal, Z. H. Peng, O. Buisson, B. Gilles, C. B. Winkelmann, and H. Courtois

Appl. Phys. Lett. 100, 252602 (2012); http://dx.doi.org/10.1063/1.4729779 (4 pages) | Cited 1 time

Online Publication Date: 22 June 2012

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A method to fabricate large-area superconducting hybrid tunnel junctions with a suspended central normal metal part is presented. The samples are fabricated by combining photo-lithography and chemical etch of a superconductor—insulator—normal metal multilayer. The process involves few fabrication steps, is reliable and produces extremely high-quality tunnel junctions. Under an appropriate voltage bias, a significant electronic cooling is demonstrated. We analyze semi-quantitatively the thermal behavior of a typical device.
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85.25.Cp Josephson devices
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Experimental and ab initio investigations of the x-ray absorption near edge structure of orthorhombic LuMnO3

Y. Hu, C. N. Borca, E. Kleymenov, M. Nachtegaal, B. Delley, M. Janousch, A. Dönni, M. Tachibana, H. Kitazawa, E. Takayama-Muromachi, M. Kenzelmann, C. Niedermayer, T. Lippert, A. Wokaun, and C. W. Schneider

Appl. Phys. Lett. 100, 252901 (2012); http://dx.doi.org/10.1063/1.4729002 (4 pages)

Online Publication Date: 18 June 2012

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X-ray near edge absorption spectroscopy was used to probe the electronic structure of multiferroic orthorhombic LuMnO3 polycrystalline samples and strained, twin-free orthorhombic (1–10) LuMnO3 films grown by pulsed laser deposition on (1–10) YAlO3 substrates. For all o-LuMnO3 samples x-ray near edge absorption spectroscopy spectra reveal that the pre-edge structure is influenced by the increase in MnO6 distortion as a result of the smaller Re-ion or film strain. Furthermore there is clear evidence of anisotropic Mn-O bonding and Mn orbital ordering along the c- and [110] direction. The experimental film and bulk data are in agreement with ab initio simulations.
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71.20.Ps Other inorganic compounds
78.70.Dm X-ray absorption spectra
81.15.Fg Pulsed laser ablation deposition
68.55.aj Insulators
71.15.-m Methods of electronic structure calculations

Dielectric relaxation and magneto-dielectric effect in polycrystalline Bi0.9Ca0.1FeO2.95

B. Ramachandran, A. Dixit, R. Naik, G. Lawes, and M. S. Ramachandra Rao

Appl. Phys. Lett. 100, 252902 (2012); http://dx.doi.org/10.1063/1.4729415 (4 pages) | Cited 3 times

Online Publication Date: 18 June 2012

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We have investigated temperature, frequency, and magnetic field dependent dielectric properties of polycrystalline Bi0.9Ca0.1FeO2.95. Two dielectric anomalies, near 65 K and 260 K, were observed with the anomaly near 65 K exhibiting distinct frequency dependence as the peak temperature shifts with increasing frequency. The low-temperature dielectric relaxation data that can be fitted to a Vogel-Fulcher expression yielding a characteristic relaxation time of ∼10−8 s are four orders larger than that of pure BiFeO3 which may be the resultant of the chemical pressure induced by Ca doping. We also observed a switchable magneto-dielectric response in Bi0.9Ca0.1FeO2.95 at room temperature.
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77.22.Gm Dielectric loss and relaxation
61.72.up Other materials
75.85.+t Magnetoelectric effects, multiferroics

Potential barrier increase due to Gd doping of BiFeO3 layers in Nb:SrTiO3-BiFeO3-Pt structures displaying diode-like behavior

H. Khassaf, G. A. Ibanescu, I. Pintilie, I. B. Misirlioglu, and L. Pintilie

Appl. Phys. Lett. 100, 252903 (2012); http://dx.doi.org/10.1063/1.4729816 (4 pages) | Cited 1 time

Online Publication Date: 19 June 2012

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The rectifying properties of Nb:SrTiO3-Bi1−xGdxFeO3-Pt structures (x = 0, 0.05, 0.1) displaying diode-like behavior were investigated via current-voltage characteristics at different temperatures. The potential barrier was estimated for negative polarity assuming a Schottky-like thermionic emission with injection controlled by the interface and the drift controlled by the bulk. The height of the potential barrier at the Nb:SrTiO3-Bi1−xGdxFeO3 interface increases with Gd doping. The results are explained by the partial compensation of the p-type conduction due to Bi vacancies with Gd doping in addition to the shift of the Fermi level towards the middle of the bandgap with increasing dopant concentration.
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73.40.Ei Rectification
73.40.Ns Metal-nonmetal contacts
79.40.+z Thermionic emission
61.72.jd Vacancies

First-principles insights on the magnetism of cubic SrTi1−xCoxO3−δ

J. M. Florez, S. P. Ong, M. C. Onbaşli, G. F. Dionne, P. Vargas, G. Ceder, and C. A. Ross

Appl. Phys. Lett. 100, 252904 (2012); http://dx.doi.org/10.1063/1.4729830 (5 pages) | Cited 1 time

Online Publication Date: 19 June 2012

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We present hybrid density functional calculations suggesting that magnetism in cubic SrTi1−xCoxO3−δ (STCO) with x = 0.25 is sensitive to the nearest neighbor arrangement of the Co and the presence of oxygen vacancies. Spin polarized calculations for x = 0.25 in which the nearest neighbor (nn) Co spacing is a, matha or matha with a the lattice parameter predict lowest energies for the matha nn separation and favor the ferromagnetic state. Oxygen deficiency (δ = 0.125) lowers the average Co valence state and favors mixed valence and spin states (high spin for the Co adjacent to the vacancy and low for the non-adjacent Co), an increase of the band gap and an expansion of the lattice parameter compared to stoichiometric STCO in which both Co ions are low spin. Predicted configurations of the two neighboring Co ions are (t2g5eg0, t2g5eg0) and (t2g4eg2, t2g6eg0) with average 1.0 and 1.6 μB/Co for stoichiometric and 1-O-vacancy systems, respectively.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.66.Bi Elemental solids
61.66.Dk Alloys
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.20.Ps Other inorganic compounds
71.55.Ht Other nonmetals
75.50.Dd Nonmetallic ferromagnetic materials

Tailoring non-linear dielectric properties by local field engineering in anisotropic porous ferroelectric structures

Leontin Padurariu, Lavinia Curecheriu, Carmen Galassi, and Liliana Mitoseriu

Appl. Phys. Lett. 100, 252905 (2012); http://dx.doi.org/10.1063/1.4729878 (5 pages) | Cited 1 time

Online Publication Date: 20 June 2012

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A method to control the nonlinear dielectric properties in porous anisotropic ceramics is proposed. The local field distributions in anisotropic porous ceramic structures were determined and the field-induced permittivity was estimated in parallel and perpendicular configurations (with respect to the pore orientation vs. the applied field direction). The predicted tunability behavior agrees well with the measured values obtained for Pb(Zr0.52Ti0.48)Nb0.024O3 ceramics with different anisotropic porosity levels. The paper demonstrates the concept of engineered local fields in porous microstructures for tailoring the permittivity and tunability values and the possibility to increase tunability with reducing permittivity for small porosity levels.
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77.22.Ch Permittivity (dielectric function)
61.43.Gt Powders, porous materials
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates

Structure and electrical properties of 〈001〉 textured (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 lead-free piezoelectric ceramics

S. K. Ye, J. Y. H. Fuh, and L. Lu

Appl. Phys. Lett. 100, 252906 (2012); http://dx.doi.org/10.1063/1.4730378 (4 pages) | Cited 2 times

Online Publication Date: 20 June 2012

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〈001〉 textured (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 (BCTZ) lead-free piezoelectric ceramics were prepared by templated-grain growth method using BaTiO3 as template. The degree of orientation and the microstructure of the ceramics with different amount of template were investigated. The electrical properties of the textured-ceramics in the optimized condition were dramatically enhanced compared with randomly-oriented BCTZ ceramics. The textured BCTZ ceramics showed high piezoelectric constants d33 = 470 pC/N and d31 = −170 pC/N, and high electromechanical coupling factors kp = 44% and k31 = 22%. In addition, the Curie point of the textured ceramics revealed an increase with the template content.
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77.65.Bn Piezoelectric and electrostrictive constants
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
77.80.B- Phase transitions and Curie point
77.22.Ch Permittivity (dielectric function)

Intermolecular interactions and high dielectric energy storage density in poly(vinylidene fluoride-hexafluoropropylene)/poly(vinylidene fluoride) blend thin films

Mojtaba Rahimabady, Kui Yao, Saeid Arabnejad, Li Lu, Victor P. W. Shim, and Davy Cheong Wun Chet

Appl. Phys. Lett. 100, 252907 (2012); http://dx.doi.org/10.1063/1.4730603 (4 pages) | Cited 1 time

Online Publication Date: 22 June 2012

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Homogeneous poly(vinylidene fluoride-hexafluoropropylene) and poly (vinylidene fluoride) (P(VDF-HFP)/PVDF) blend films were prepared via a chemical solution approach, followed by quenching, annealing, and hot pressing. The intermolecular interactions of the blends were investigated through atomic simulation. Higher melting temperature, higher crystallinity, larger elastic modulus, and improved breakdown strength (>850 MV/m) were observed in the optimized polymer blends, in comparison with either of the two constituent polymers, PVDF or P(VDF-HFP). In addition, the P(VDF-HFP)/PVDF blend film also showed larger dielectric constant. As a result, an extremely high energy density of 30.1 J/cm3 was achieved in P(VDF-HFP)/PVDF (50:50 by weight) blend films.
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77.22.Ch Permittivity (dielectric function)
77.22.Jp Dielectric breakdown and space-charge effects
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli
68.55.am Polymers and organics
61.41.+e Polymers, elastomers, and plastics

Epitaxial growth and capacitance-voltage characteristics of BiFeO3/CeO2/yttria-stabilized zirconia/Si(001) heterostructure

Zhongqiang Hu, Meiya Li, Yongdan Zhu, Shizhou Pu, Xiaolian Liu, Bobby Sebo, Xingzhong Zhao, and Shuxiang Dong

Appl. Phys. Lett. 100, 252908 (2012); http://dx.doi.org/10.1063/1.4730621 (4 pages) | Cited 1 time

Online Publication Date: 22 June 2012

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We report the epitaxial growth of multiferroic BiFeO3 (BFO) film on Si(001) substrate by pulsed laser deposition using CeO2/yttria-stabilized zirconia (YSZ) as buffer layers. The epitaxial relationships of the films were BFO(001)/CeO2(001)/YSZ(001)/Si(001) for out-of-plane and [110]BFO‖[100]CeO2‖[100]YSZ‖[100]Si for in-plane, respectively. Capacitance-voltage characteristics of a Pt/BFO/CeO2/YSZ/p-Si capacitor exhibited clockwise hysteresis loops with a large memory window of 2.5 V at sweeping voltages of ±16 V. Both the high and low capacitance values showed no obvious degradation after 104 s. The improved retention property was attributed to the use of high-k CeO2/YSZ insulating layers that effectively eliminated the charge trapping in the heterostructure.
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77.55.fp Other ferroelectric films
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.80.Dj Domain structure; hysteresis
81.15.Fg Pulsed laser ablation deposition
68.55.aj Insulators
75.85.+t Magnetoelectric effects, multiferroics
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Large-scale fabrication of plasmonic gold nanohole arrays for refractive index sensing at visible region

Ke Cheng, Shujie Wang, Zhonggang Cui, Qianqian Li, Shuxi Dai, and Zuliang Du

Appl. Phys. Lett. 100, 253101 (2012); http://dx.doi.org/10.1063/1.4728987 (4 pages) | Cited 1 time

Online Publication Date: 18 June 2012

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We present the design and fabrication of large-scale gold nanohole arrays based on the versatile nanosphere lithography technique. The gold nanohole arrays exhibit two surface plasmonic resonance related transmission peaks and show a sensitive response to refractive index. The working wavelength and sensitivity can be tuned by changing the hole diameter and hole depth. A sensitivity of 125 nm/refractive index unit is obtained in the visible region. Our quasi-infinite gold nanohole arrays film can serve as an optical enhancing component while also can serve as a transparent conductive electrode for the opto-electric devices.
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81.16.-c Methods of micro- and nanofabrication and processing
61.46.-w Structure of nanoscale materials
68.55.-a Thin film structure and morphology
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Bz Metals and metallic alloys

Direct manipulation of the uncompensated antiferromagnetic spins in exchange coupled system by GeV ion irradiation

Amitesh Paul, N. Paul, C. Trautmann, S. Mattauch, Jaru Jutimoosik, Rattikorn Yimnirun, Saroj Rujirawat, Britta Höpfner, Iver Lauermann, M. Lux-Steiner, and P. Böni

Appl. Phys. Lett. 100, 253102 (2012); http://dx.doi.org/10.1063/1.4729472 (5 pages)

Online Publication Date: 18 June 2012

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Incident ion energy to matrix electrons of a material is dissipated within a narrow cylinder surrounding the swift heavy ion path. The temperature of the lattice exceeds the melting point and upon quenching causes nanometric modifications. We present here a unique ex situ approach in manipulating the uncompensated spins in antiferromagnetic layers of ferro-/antiferromagnetic exchange coupled systems on a nanometric scale. We use the impact of relativistic heavy ion (1–2 GeV) irradiation on such systems. We find an increase in the bias field and a restoration of the reversal via domain nucleation in the trained state. These are identified as plausible results of ion-induced antiferromagnetic ordering with little or no effect on the layer structure. This study demonstrates, therefore, the possibility of nanoscale tailoring of exchange coupled systems that survive even in the trained state.
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61.80.Jh Ion radiation effects
75.50.Ee Antiferromagnetics
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ch Domain walls and domain structure
75.75.-c Magnetic properties of nanostructures
75.30.Et Exchange and superexchange interactions

Ultrafast photoluminescence from freestanding Si nanocrystals

Sung Kim, Dong Hee Shin, and Suk-Ho Choi

Appl. Phys. Lett. 100, 253103 (2012); http://dx.doi.org/10.1063/1.4729605 (3 pages)

Online Publication Date: 18 June 2012

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SiO1.2/SiO2 multilayers were grown on n-type (100) Si wafers by ion beam sputtering and subsequently annealed at 1100 °C to form SiO2-embedded Si (S-Si) nanocrystals (NCs). The SiO2 matrix was then removed from S-Si NCs by chemical treatments to prepare freestanding Si (F-Si) NCs. The photoluminescence (PL) peak of F-Si NCs at ∼657 nm (1.89 eV) is blue-shifted with respect to that of S-Si NCs at ∼816 nm (1.52 eV). The peak shift of ∼0.37 eV is much larger than what is expected by the quantum confinement effect. The PL lifetime of F-Si NCs (∼3 ns) is much shorter than that of S-Si NCs (∼50 μs). Possible physical mechanisms are discussed to explain the origin of the fast PL band found in F-Si NCs.
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78.55.Hx Other solid inorganic materials
81.16.Be Chemical synthesis methods
81.40.Gh Other heat and thermomechanical treatments
81.07.Bc Nanocrystalline materials
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
68.65.Ac Multilayers

Ultrathin metallic coatings can induce quantum levitation between nanosurfaces

Mathias Boström, Barry W. Ninham, Iver Brevik, Clas Persson, Drew F. Parsons, and Bo E. Sernelius

Appl. Phys. Lett. 100, 253104 (2012); http://dx.doi.org/10.1063/1.4729822 (4 pages) | Cited 2 times

Online Publication Date: 19 June 2012

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There is an attractive Casimir-Lifshitz force between two silica surfaces in a liquid (bromobenze or toluene). We demonstrate that adding an ultrathin (5–50 Å) metallic nanocoating to one of the surfaces results in repulsive Casimir-Lifshitz forces above a critical separation. The onset of such quantum levitation comes at decreasing separations as the film thickness decreases. Remarkably, the effect of retardation can turn attraction into repulsion. From that we explain how an ultrathin metallic coating may prevent nanoelectromechanical systems from crashing together.
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78.66.Bz Metals and metallic alloys

Threshold switching via electric field induced crystallization in phase-change memory devices

Jorge A. Vázquez Diosdado, Peter Ashwin, Krisztian I. Kohary, and C. David Wright

Appl. Phys. Lett. 100, 253105 (2012); http://dx.doi.org/10.1063/1.4729551 (4 pages) | Cited 4 times

Online Publication Date: 19 June 2012

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Phase-change devices exhibit characteristic threshold switching from the reset (off) to the set (on) state. Mainstream understanding of this electrical switching phenomenon is that it is initiated electronically via the influence of high electric fields on inter-band trap states in the amorphous phase. However, recent work has suggested that field induced (crystal) nucleation could instead be responsible. We compare and contrast these alternative switching “theories” via realistic simulations of device switching both with and without electric field dependent contributions to the system free energy. Results show that although threshold switching can indeed be obtained purely by electric field induced nucleation, the fields required are significantly larger than experimentally measured values.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
84.30.Sk Pulse and digital circuits

Design of a surface acoustic wave mass sensor in the 100 GHz range

Damiano Nardi, Elisa Zagato, Gabriele Ferrini, Claudio Giannetti, and Francesco Banfi

Appl. Phys. Lett. 100, 253106 (2012); http://dx.doi.org/10.1063/1.4729624 (4 pages) | Cited 1 time

Online Publication Date: 19 June 2012

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A design for photoacoustic mass sensors operating above 100 GHz is proposed. The design is based on impulsive optical excitation of a pseudosurface acoustic wave in a surface phononic crystal with nanometric periodic grating and on time-resolved extreme ultraviolet detection of the pseudosurface acoustic wave frequency shift upon mass loading the device. The present design opens the path to sensors operating in a frequency range currently unaccessible to electro-acoustical transducers, providing enhanced sensitivity, miniaturization, and incorporating time-resolving capability while forgoing the piezoelectric substrate requirement.
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43.58.-e Acoustical measurements and instrumentation
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
85.60.Gz Photodetectors (including infrared and CCD detectors)
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