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28 Sep 2009

Volume 95, Issue 13, Articles (13xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 95, 131107 (2009); http://dx.doi.org/10.1063/1.3236752 (3 pages)

Marcus Eichfelder, Wolfgang-Michael Schulz, Matthias Reischle, Michael Wiesner, Robert Roßbach, Michael Jetter, and Peter Michler
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Electrical stress-induced instability of amorphous indium-gallium-zinc oxide thin-film transistors under bipolar ac stress

Sangwon Lee, Kichan Jeon, Jun-Hyun Park, Sungchul Kim, Dongsik Kong, Dong Myong Kim, Dae Hwan Kim, Sangwook Kim, Sunil Kim, Jihyun Hur, Jae Chul Park, Ihun Song, Chang Jung Kim, Youngsoo Park, and U-In Jung

Appl. Phys. Lett. 95, 132101 (2009); http://dx.doi.org/10.1063/1.3237169 (3 pages) | Cited 11 times

Online Publication Date: 28 September 2009

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Bipolar ac stress-induced instability of amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors is comparatively investigated with that under a positive dc gate bias stress. While the positive dc gate bias stress-induced threshold voltage shift (ΔVT) is caused by the charge trapping into the interface/gate dielectric as reported in previous works, the dominant mechanism of the ac stress-induced ΔVT is observed to be due to the increase in the acceptorlike deep states of the density of states (DOS) in the a-IGZO active layer. Furthermore, it is found that the variation of deep states in the DOS makes a parallel shift in the IDS-VGS curve with an insignificant change in the subthreshold slope, as well as the deformation of the CG-VG curves.
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85.30.Tv Field effect devices
81.15.Cd Deposition by sputtering
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.Ga II-VI semiconductors
71.55.Gs II-VI semiconductors
81.05.Dz II-VI semiconductors

ZnO(0001) surfaces probed by scanning tunneling spectroscopy: Evidence for an inhomogeneous electronic structure

J. Dumont, B. Hackens, S. Faniel, P.-O. Mouthuy, R. Sporken, and S. Melinte

Appl. Phys. Lett. 95, 132102 (2009); http://dx.doi.org/10.1063/1.3238288 (3 pages) | Cited 4 times

Online Publication Date: 28 September 2009

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The stability of the polar Zn-terminated ZnO surface is probed by low-temperature scanning tunneling microscopy and scanning tunneling spectroscopy (STS). Surface states in the bandgap of ZnO are evidenced by STS and their presence is correlated with the local surface corrugation. Very defective surface regions are characterized by a bulk electronic structure showing a wide bandgap while nanometer-scale defect free regions exhibit a narrower bandgap and surface states. We also image atomically resolved (math×math)R30° reconstructions on the defect-free areas.
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73.20.At Surface states, band structure, electron density of states
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
71.20.Nr Semiconductor compounds

Orientation-controlled Si thin films on insulating substrates by Al-induced crystallization combined with interfacial-oxide layer modulation

Masashi Kurosawa, Naoyuki Kawabata, Taizoh Sadoh, and Masanobu Miyao

Appl. Phys. Lett. 95, 132103 (2009); http://dx.doi.org/10.1063/1.3241076 (3 pages) | Cited 18 times

Online Publication Date: 29 September 2009

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Orientation-controlled Si films on transparent insulating substrates are strongly desired to achieve high-efficiency thin-film solar cells. We have developed the interfacial-oxide layer modulated Al-induced low temperature (<450 °C) crystallization technique, which enables dominantly (001) or (111)-oriented Si films with large grains (20–100 μm). These results are qualitatively explained on the basis of a model considering the phase transition of the interfacial Al oxide layers. This process provides the orientation-controlled Si templates on insulating substrates, which enables successive high quality epitaxial growth necessary for advanced Si thin-film solar cells.
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68.55.ag Semiconductors
64.70.dg Crystallization of specific substances
84.60.Jt Photoelectric conversion

Surface structure and chemical states of a-plane and c-plane InN films

Takahiro Nagata, Gregor Koblmüller, Oliver Bierwagen, Chad S. Gallinat, and James S. Speck

Appl. Phys. Lett. 95, 132104 (2009); http://dx.doi.org/10.1063/1.3238286 (3 pages) | Cited 13 times

Online Publication Date: 29 September 2009

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The surface electron accumulation layer, surface structure, and surface chemical states of a-plane (nonpolar) and c-plane (polar) InN epitaxial films were investigated. Electrical measurements indicated electron accumulation layers on the surface of both the InN films. Angle-resolved x-ray photoelectron spectroscopy (XPS) measurements indicated a strong band bending at both surfaces, thus confirming the surface electron accumulation. Further XPS analysis of the near-surface chemical states indicated an In adlayer at the surface of c-plane InN and an oxygen adsorbed layer on the a-plane InN. These results suggest different ad-layers to cause the surface electron accumulation on c-plane and a-plane InN.
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68.35.bg Semiconductors
68.55.-a Thin film structure and morphology
79.60.Dp Adsorbed layers and thin films
73.20.At Surface states, band structure, electron density of states
68.43.Fg Adsorbate structure (binding sites, geometry)

Large Rashba splitting in highly asymmetric CdTe/PbTe/PbSrTe quantum well structures

Shuqiang Jin, Huizhen Wu, and Tianning Xu

Appl. Phys. Lett. 95, 132105 (2009); http://dx.doi.org/10.1063/1.3236531 (3 pages) | Cited 3 times

Online Publication Date: 29 September 2009

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The realization of PbTe/CdTe quantum structures and determination of highly asymmetric energy band make it feasible to construct asymmetric CdTe/PbTe/Pb1−xSrxTe quantum wells (QWs) for the probe of spintronics. Contrary to HgTe/CdTe QWs, the spin-orbit interaction in the CdTe/PbTe/Pb1−xSrxTe QWs is purely Rashba and anisotropic. Rashba splittings in the asymmetric QWs with different growth orientations and electron densities are explored. For the QWs grown along [110] direction the Rashba splitting for the oblique valley is particularly large (13.7 meV). The strong Rashba effect presented in the highly asymmetric QWs provides a potential candidate for spintronic devices.
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73.21.Fg Quantum wells
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
72.25.Dc Spin polarized transport in semiconductors
71.20.Nr Semiconductor compounds

Current-controlled magnetoresistance in silicon in non-Ohmic transport regimes

Michael P. Delmo, Shinya Kasai, Kensuke Kobayashi, and Teruo Ono

Appl. Phys. Lett. 95, 132106 (2009); http://dx.doi.org/10.1063/1.3238361 (3 pages) | Cited 8 times

Online Publication Date: 30 September 2009

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We show that the large positive magnetoresistance in nonmagnetic silicon devices can be controlled by a current applied in the non-Ohmic transport regime. The experimental results indicate that the carrier transport in this regime is dominated by the space-charge effect, where the magnetoresistance effect is greatly enhanced. We propose a device concept based on the space-charge-induced magnetoresistance effect in silicon that is controlled by both the current and the magnetic field, which looks similar to the characteristics of the field-effect transistors.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
72.20.Fr Low-field transport and mobility; piezoresistance
85.30.Fg Bulk semiconductor and conductivity oscillation devices (including Hall effect devices, space-charge-limited devices, and Gunn effect devices)
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Nonlinear conductivity of electronic origin in self-doped LaMnO3+δ

B. Fisher, J. Genossar, L. Patlagan, and G. M. Reisner

Appl. Phys. Lett. 95, 132501 (2009); http://dx.doi.org/10.1063/1.3242008 (3 pages) | Cited 3 times

Online Publication Date: 30 September 2009

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We report on electronic transport measurements on polycrystalline, nonmetallic samples of LaMnO3+δ, in the Ohmic and non-Ohmic regimes. The non-Ohmic regime has been investigated using single current pulses of short duration. The large nonlinearity of the pulsed I-V characteristics is probably of the same origin as that of the nonmetallicity of LaMnO3+δ, that is, disorder introduced by Mn vacancies. The dc I-V characteristics, under similar fields, show much larger nonlinearity and hysteresis, typical of self-heating in samples with activated conductivity.
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72.20.Ht High-field and nonlinear effects
72.20.My Galvanomagnetic and other magnetotransport effects
72.80.Sk Insulators
61.72.jd Vacancies
75.47.Gk Colossal magnetoresistance
75.47.Lx Magnetic oxides

First-principle study on the magnetic properties of six potential half-metallic ferromagnets: C-doped alkaline-earth chalcogenides

J. Liu, L. Chen, H. -N. Dong, and R. -L. Zheng

Appl. Phys. Lett. 95, 132502 (2009); http://dx.doi.org/10.1063/1.3242013 (3 pages) | Cited 6 times

Online Publication Date: 30 September 2009

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Six half-metallic ferromagnets with NaCl structure, X4CY3 (X = Mg, Ca, and Sr and Y = O and S) are predicted by the first principle calculations based on the density functional theory. The supercell magnetic moments of these ferromagnets are all integer 2.0μB, which are one of important characters of half-metallic ferromagnets. Our calculations indicate that X4CY3 have wide spin gap and potentially have high Curie temperature. C-doping results in the spin-polarization and half-metallicity of these alkaline-earth chalcogenides. The main reason is that there are sp hybridized orbitals in X4CY3, and two outer-shell s-electrons of alkaline-earth ions enter into sp hybridized orbitals in parallel.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Dd Nonmetallic ferromagnetic materials
72.25.-b Spin polarized transport
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.Mg Numerical simulation studies

Timing jitter of cascade switch superconducting nanowire single photon detectors

M. Ejrnaes, A. Casaburi, R. Cristiano, O. Quaranta, S. Marchetti, N. Martucciello, S. Pagano, A. Gaggero, F. Mattioli, R. Leoni, P. Cavalier, and J. -C. Villégier

Appl. Phys. Lett. 95, 132503 (2009); http://dx.doi.org/10.1063/1.3237172 (3 pages) | Cited 7 times

Online Publication Date: 30 September 2009

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We investigate the timing jitter in parallel superconducting NbN-nanowire single photon detectors based on a cascade switch mechanism. The measured timing jitter is asymmetric and has an oscillatory dependence on bias current. At the highest bias current the full width at half maximum was 1.5 times larger than an on-chip reference meander NbN nanowire. A physical model of the dynamics occurring during cascade switch is developed, that quantitatively accounts for our observations as a consequence of different nanowire critical currents within the detector.
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85.25.Oj Superconducting optical, X-ray, and γ-ray detectors (SIS, NIS, transition edge)
74.25.Sv Critical currents
85.35.-p Nanoelectronic devices
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Large reversible magnetocaloric effect caused by two successive magnetic transitions in ErGa compound

J. Chen, B. G. Shen, Q. Y. Dong, F. X. Hu, and J. R. Sun

Appl. Phys. Lett. 95, 132504 (2009); http://dx.doi.org/10.1063/1.3233925 (3 pages) | Cited 16 times

Online Publication Date: 30 September 2009

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Intermetallic compound ErGa exhibits two successive magnetic transitions: spin-reorientation transition at TSR = 15 K and ferromagnetic-paramagnetic transition at TC = 30 K. Both transitions contribute greatly to the magnetic entropy change (ΔSM), each yielding a significant peak on their ΔSM-T curve and thus a considerable value of refrigerant capacity (RC) without hysteresis loss. For a magnetic field change of 5 T, the maximal values of −ΔSM are 21.3 J/kg K at TC and 16.5 J/kg K at TSR, with an RC value of 494 J/kg. Large reversible magnetocaloric effect and RC indicate the potentiality of ErGa as a candidate magnetic refrigerant at low temperatures.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
65.40.gd Entropy
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Giant reversible magnetocaloric effect in antiferromagnetic superconductor Dy0.9Tm0.1Ni2B2C compound

Lingwei Li and Katsuhiko Nishimura

Appl. Phys. Lett. 95, 132505 (2009); http://dx.doi.org/10.1063/1.3240399 (3 pages) | Cited 13 times

Online Publication Date: 30 September 2009

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The magnetic properties and magnetocaloric effect in antiferromagnetic superconductor Dy0.9Tm0.1Ni2B2C compound have been studied. The magnetic phase transition TM ( ∼ 9.2 K) occurs above the superconducting transition temperature Tc ( ∼ 4.5 K). A giant reversible magnetocaloric effect has been observed, which is related to a field-induced first order metamagnetic transition from antiferromagnetic to ferromagnetic state. The values of maximum magnetic entropy change (−ΔSMmax) reach 14.7 and 19.1 J kg−1 K−1 for the field change of 5 and 7 T with no obvious hysteresis loss around 13 K, respectively. These results indicated that Dy0.9Tm0.1Ni2B2C could be a promising candidate for magnetic refrigeration at low temperatures.
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74.25.Ha Magnetic properties including vortex structures and related phenomena
75.50.Ee Antiferromagnetics
74.10.+v Occurrence, potential candidates
75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
74.70.-b Superconducting materials other than cuprates

Crossover of angular dependent magnetoresistance with the metal-insulator transition in colossal magnetoresistive manganite films

Y. Z. Chen, J. R. Sun, T. Y. Zhao, J. Wang, Z. H. Wang, B. G. Shen, and N. Pryds

Appl. Phys. Lett. 95, 132506 (2009); http://dx.doi.org/10.1063/1.3240407 (3 pages) | Cited 8 times

Online Publication Date: 1 October 2009

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The temperature and magnetic field dependence of angular dependent magnetoresistance (AMR) along two orthogonal directions ([100] and [0math1]) was investigated in a charge-orbital-ordered Sm0.5Ca0.5MnO3 (SCMO) film grown on (011)-oriented SrTiO3 substrates. A dramatic decrease of AMR magnitude in both directions was observed with the appearance of magnetic-field-induced metal-insulator transition, which further led to a sign crossover in the AMR effect. The AMR crossover may give a direct evidence of the drastic modification of electronic structure or possible orbital reconstruction with the magnetic-destruction of charge/orbital ordering in SCMO films.
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75.70.Ak Magnetic properties of monolayers and thin films
71.20.Ps Other inorganic compounds
81.15.Fg Pulsed laser ablation deposition
71.30.+h Metal-insulator transitions and other electronic transitions
75.47.Lx Magnetic oxides
75.47.Gk Colossal magnetoresistance

Epitaxial growth and magnetoelectric relaxor behavior in multiferroic 0.8Pb(Fe1/2Nb1/2)O3–0.2Pb(Mg1/2W1/2)O3 thin films

Wei Peng, N. Lemée, J.-L. Dellis, V. V. Shvartsman, P. Borisov, W. Kleemann, Z. Trontelj, J. Holc, M. Kosec, R. Blinc, and M. G. Karkut

Appl. Phys. Lett. 95, 132507 (2009); http://dx.doi.org/10.1063/1.3242377 (3 pages) | Cited 5 times

Online Publication Date: 2 October 2009

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We present electric and magnetic properties of 0.8Pb(Fe1/2Nb1/2)O3–0.2Pb(Mg1/2W1/2)O3 films epitaxially grown on (001) SrTiO3 substrates using pulsed laser deposition. A narrow deposition window around 710 °C and 0.2 mbar has been identified to achieve epitaxial single-phase thin films. A typical Vogel–Fulcher relaxorlike dielectric and magnetic susceptibility dispersion is observed, suggesting magnetoelectric relaxor behavior in these films similar to the bulk. We determine a magnetic cluster freezing temperature of 36 K, while observing weak ferromagnetism via magnetic hysteresis loops up to 300 K.
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75.80.+q Magnetomechanical effects, magnetostriction
75.50.Dd Nonmetallic ferromagnetic materials
81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
77.22.Ch Permittivity (dielectric function)
75.30.Cr Saturation moments and magnetic susceptibilities

Conversion of magnetic structure by slight dopants in geometrically frustrated antiperovskite Mn3GaN

K. Takenaka, T. Inagaki, and H. Takagi

Appl. Phys. Lett. 95, 132508 (2009); http://dx.doi.org/10.1063/1.3243340 (3 pages) | Cited 6 times

Online Publication Date: 2 October 2009

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We found that a few percent of Fe dopants at the Mn sites alters the antiferromagnetic spin structure of Mn3GaN and induces a first-order antiferromagnetic-ferromagnetic phase transition accompanied by a large volume change. The drastic conversion of the spin alignment originates from phase competition due to a geometrical frustration in the Mn6N octahedron. This result demonstrates that the magnetic and other unique related properties of manganese antiperovskites are controllable by element substitution. Comparing with the ferromagnetic state in Mn3Ga(N1−xCx), we discuss a possible spin structure that accounts for the conversion of the magnetic states.
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75.40.-s Critical-point effects, specific heats, short-range order
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.50.Ee Antiferromagnetics

Suppression of the perpendicular anisotropy at the CoO Néel temperature in exchange-biased CoO/[Co/Pt] multilayers

E. Shipton, K. Chan, T. Hauet, O. Hellwig, and E. E. Fullerton

Appl. Phys. Lett. 95, 132509 (2009); http://dx.doi.org/10.1063/1.3240402 (3 pages) | Cited 10 times

Online Publication Date: 2 October 2009

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We performed high field torque magnetometry measurements on CoO/[Co/Pt] magnetic multilayers that exhibit perpendicular exchange bias. We find that the antiferromagnet CoO layers strongly modify the uniaxial anisotropy of the multilayer structures. The strongest effects due to the CoO layers occur in the vicinity of the Néel temperature, where we observe a suppression of the first-order anisotropy and a smaller enhancement of the second-order anisotropy. This results in a nonmonotonic variation of the anisotropy with temperature and for selected samples a transition from perpendicular to in-plane and back to perpendicular anisotropy with increasing temperature.
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75.30.Gw Magnetic anisotropy
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.30.Et Exchange and superexchange interactions
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Ee Antiferromagnetics

Spin transfer torque switching of magnetic tunnel junctions using a conductive atomic force microscope

Eric R. Evarts, Limin Cao, David S. Ricketts, Nicholas D. Rizzo, James A. Bain, and Sara A. Majetich

Appl. Phys. Lett. 95, 132510 (2009); http://dx.doi.org/10.1063/1.3240884 (3 pages) | Cited 3 times

Online Publication Date: 2 October 2009

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We show that a nonmagnetic conductive atomic force microscopy probe can be used to read and write magnetic bits using current passed between the tip and bit. The bits were patterned using electron beam lithography from a magnetic tunnel junction (MTJ) film with in-plane shape anisotropy using an MgO tunnel barrier. Probes were made having a thick Pt coating and could deliver up to several milliamps, so that MTJ structures were easily switched repeatedly using the spin transfer torque effect.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)
85.75.Dd Magnetic memory using magnetic tunnel junctions
85.40.Hp Lithography, masks and pattern transfer
72.25.-b Spin polarized transport
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
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Y–O hybridization in the ferroelectric transition of YMnO3

Jinyoung Kim, Kyung Chul Cho, Yang Mo Koo, Kun Pyo Hong, and Namsoo Shin

Appl. Phys. Lett. 95, 132901 (2009); http://dx.doi.org/10.1063/1.3233943 (3 pages) | Cited 9 times

Online Publication Date: 28 September 2009

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The electron density distribution of paraelectric and ferroelectric YMnO3 are investigated by analyzing high temperature synchrotron radiation powder diffraction data using the maximum entropy method (MEM) and MEM-based pattern fitting combined with the Rietveld method. The results show that chemical bonding by orbital hybridization is established between the Y and in-plane O ions along the polar c-axis below the ferroelectric transition temperature. We suggest that the hybridization observed in the ferroelectric phase is the driving force for ferroelectricity in YMnO3.
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77.80.B- Phase transitions and Curie point
75.80.+q Magnetomechanical effects, magnetostriction
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
75.50.Ee Antiferromagnetics
77.22.Ej Polarization and depolarization

Shear effects in lateral piezoresponse force microscopy at 180° ferroelectric domain walls

J. Guyonnet, H. Béa, F. Guy, S. Gariglio, S. Fusil, K. Bouzehouane, J.-M. Triscone, and P. Paruch

Appl. Phys. Lett. 95, 132902 (2009); http://dx.doi.org/10.1063/1.3226654 (3 pages) | Cited 14 times

Online Publication Date: 30 September 2009

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In studies using piezoresponse force microscopy, we observe a nonzero lateral piezoresponse at 180° domain walls in out-of-plane polarized, c-axis-oriented tetragonal ferroelectric Pb(Zr0.2Ti0.8)O3 epitaxial thin films. We attribute these observations to a shear strain effect linked to the sign change of the d33 piezoelectric coefficient through the domain wall, in agreement with theoretical predictions. We show that in monoclinically distorted tetragonal BiFeO3 films, this effect is superimposed on the lateral piezoresponse due to actual in-plane polarization and has to be taken into account in order to correctly interpret the ferroelectric domain configuration.
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77.80.Dj Domain structure; hysteresis
77.65.-j Piezoelectricity and electromechanical effects
68.60.Bs Mechanical and acoustical properties

Band alignment and electron traps in Y2O3 layers on (100)Si

W. C. Wang, M. Badylevich, V. V. Afanas’ev, A. Stesmans, C. Adelmann, S. Van Elshocht, J. A. Kittl, M. Lukosius, Ch. Walczyk, and Ch. Wenger

Appl. Phys. Lett. 95, 132903 (2009); http://dx.doi.org/10.1063/1.3236536 (3 pages) | Cited 4 times

Online Publication Date: 30 September 2009

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Y2O3 films deposited by atomic vapor deposition on (100)Si with a 2 or 5 nm thick pregrown thermal SiO2 are investigated as possible charge trapping layers. Analysis of these structures using spectroscopic ellipsometry, photoconductivity, and internal photoemission reveals that Y2O3 has a 5.6 eV wide optical bandgap and a 2.0 eV conduction band offset with silicon. Photo(dis)charging experiments show that the optical energy depth of most of the traps exceeds 1.5 eV with respect to the Y2O3 conduction band, explaining the observed charge retention time of ∼ 108 s at room temperature, even in the absence of a blocking insulator.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
68.55.at Other materials
72.40.+w Photoconduction and photovoltaic effects
73.61.Ng Insulators
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.66.Nk Insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
79.60.Jv Interfaces; heterostructures; nanostructures

Improved dielectric strength of barium titanate-polyvinylidene fluoride nanocomposite

Xiaoliang Dou, Xiaolin Liu, Yong Zhang, Huan Feng, Jian-Feng Chen, and Song Du

Appl. Phys. Lett. 95, 132904 (2009); http://dx.doi.org/10.1063/1.3242004 (3 pages) | Cited 9 times

Online Publication Date: 2 October 2009

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Barium titanate-polyvinydene fluoride nanocomposites with improved dielectric strength were prepared, in which on the surface of the barium titanate nanoparticle was coated. The results showed that the dielectric breakdown strength of the nanocomposites increase significantly up to 250 kV/mm and then decrease. Microstructural investigations revealed that the coated barium titanate nanoparticles were well-dispersed in polyvinydene fluoride. Fourier transform infrared spectroscopy confirmed that there is a large coverage of cross-linking in both interfaces of the barium titanate–titanate and the titanate–polyvinydene fluoride, which can connect the composites to form an organically integrated body, which result in the increase of the dielectric strength of the nanocomposites.
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77.22.Jp Dielectric breakdown and space-charge effects
81.16.-c Methods of micro- and nanofabrication and processing
77.84.Lf Composite materials
81.07.Pr Organic-inorganic hybrid nanostructures
78.30.-j Infrared and Raman spectra

Ionized-oxygen vacancies related dielectric relaxation in heteroepitaxial K0.5Na0.5NbO3/La0.67Sr0.33MnO3 structure at elevated temperature

J. Miao, X. G. Xu, Y. Jiang, L. X. Cao, and B. R. Zhao

Appl. Phys. Lett. 95, 132905 (2009); http://dx.doi.org/10.1063/1.3242009 (3 pages) | Cited 9 times

Online Publication Date: 2 October 2009

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Ferroelectric K0.5Na0.5NbO3 (KNN) thin film was epitaxially grown on La0.67Sr0.33MnO3 (LSMO) buffered LaAlO3 substrate by pulse laser deposition. The crystallographic structure of KNN/LSMO was confirmed by x-ray diffraction. Interestingly, a dielectric relaxor feature was found in the temperature range 200–350 °C. The activation energies for relaxation and conduction of the films were found to be 1.87 and 0.63–0.71 eV, respectively. The mechanism for dielectric relaxation in KNN/LSMO structure was discussed under a thermally activated process. The remnant polarization and coercive field of the films were 21.3 μC/cm2 and 91 kV/cm, respectively.
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77.22.Gm Dielectric loss and relaxation
77.80.-e Ferroelectricity and antiferroelectricity
77.55.-g Dielectric thin films
81.15.Fg Pulsed laser ablation deposition
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Influence of a static magnetic field on the photoluminescence of an ensemble of nitrogen-vacancy color centers in a diamond single-crystal

Ngoc Diep Lai, Dingwei Zheng, Fedor Jelezko, François Treussart, and Jean-François Roch

Appl. Phys. Lett. 95, 133101 (2009); http://dx.doi.org/10.1063/1.3238467 (3 pages) | Cited 8 times

Online Publication Date: 28 September 2009

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We investigate the electron spin resonance of an ensemble of nitrogen-vacancy (NV) color centers in a bulk diamond crystal. The four possible orientations of the NV center in the lattice lead to different dependences on the magnitude and the orientation of an external static magnetic field. Experimental results obtained with a continuous microwave excitation are in good agreement with simulations. In addition, we observe that the average radiative lifetime of the NV color center is also modified when the external magnetic field is applied. This variation is explained by the mixing between mS = 0 and mS = ±1 spin states of the NV center with different radiative lifetimes, due to magnetic coupling. These results are of interest for a broad range of applications, such as spin-resonance-based magnetometry with a high-density ensemble of NV centers.
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78.55.Hx Other solid inorganic materials
76.30.Mi Color centers and other defects
61.72.jn Color centers
61.72.jd Vacancies

From nanoparticle to nanocable: Impact of size and geometrical constraints on the optical modes of Si/SiO2 core/shell nanostructures

Juan Wang, Xiao-Jing Wang, Yang Jiao, Quan Li, Ming-Wen Chu, and Marek Malac

Appl. Phys. Lett. 95, 133102 (2009); http://dx.doi.org/10.1063/1.3237162 (3 pages) | Cited 3 times

Online Publication Date: 28 September 2009

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In the extinction spectra of Si/SiO2 core/shell nanostructures, peak features in the near UV region (3–5 eV) appear when the nanostructure geometrical configuration changes from spherical nanoparticles to cylindrical nanocables, with the peak features become more intense in the nanocables of smaller core diameter. Similar feature at ∼ 4.2 eV is also observed in the spatially resolved electron energy loss spectra (SREELS) of individual nanocable, but not in the nanoparticle. The EELS simulations unravel the origin of such excitation as the monopolar interface plasmon in cylindrical nano-objects, being responsible for the observed near UV extinction modes in nanocables.
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61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
78.40.Ha Other nonmetallic inorganics
78.66.-w Optical properties of specific thin films
79.20.Uv Electron energy loss spectroscopy
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Stable ferromagnetism in p-type carbon-doped ZnO nanoneedles

T. S. Herng, S. P. Lau, C. S. Wei, L. Wang, B. C. Zhao, M. Tanemura, and Y. Akaike

Appl. Phys. Lett. 95, 133103 (2009); http://dx.doi.org/10.1063/1.3238289 (3 pages) | Cited 21 times

Online Publication Date: 28 September 2009

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The authors report the synthesis and magnetic properties of carbon-doped ZnO (ZnO:C) nanoneedles. A saturated magnetic moment of 2.16 emu/cm3 was found in the ZnO:C nanoneedles. The samples showed anomalous Hall effect and p-type conduction with a hole concentration of 1.8×1018 cm−3. The ferromagnetism in the ZnO:C nanoneedles could be attributed to C substitution on the O site which introduces hole, so the p-p interaction leads to the strong spin interaction between the C atoms and carriers. It was found that the ferromagnetism and p-type conduction in the ZnO:C nanoneedles were stable in ambient air over a period of 1 year and annealing temperature of up to 100 °C.
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73.63.Nm Quantum wires
75.75.-c Magnetic properties of nanostructures
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
75.30.Cr Saturation moments and magnetic susceptibilities
73.63.Bd Nanocrystalline materials

Ultrasmall penetration depth in nanoscale thermal radiation

S. Basu and Z. M. Zhang

Appl. Phys. Lett. 95, 133104 (2009); http://dx.doi.org/10.1063/1.3238315 (3 pages) | Cited 4 times

Online Publication Date: 28 September 2009

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Near-field thermal radiation can significantly exceed that predicted by the Stefan–Boltzmann law, especially when surface polaritons are excited such that the energy transfer is through photon tunneling. The penetration depth, or skin depth, of evanescent waves is usually a few tenths of a wavelength. This letter demonstrates that an extremely small skin depth (on the order of a nanometer) can exist for nanoscale thermal radiation between two plates separated by a vacuum gap, even though the dominant wavelengths are in the infrared. Furthermore, the skin depth is proportional to the separation distance.
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44.40.+a Thermal radiation
05.60.-k Transport processes
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
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