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31 Mar 2008

Volume 92, Issue 13, Articles (13xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 92, 133501 (2008); http://dx.doi.org/10.1063/1.2901684 (3 pages)

Eric Akmansoy, Emmanuel Centeno, Kevin Vynck, David Cassagne, and Jean-Michel Lourtioz
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Obtaining the glass transition temperature by measuring the crack healing process of glassformers

J. L. Zhang, W. H. Wu, H. W. Zhou, X. Z. Guo, and Y. N. Huang

Appl. Phys. Lett. 92, 131906 (2008); http://dx.doi.org/10.1063/1.2905290 (3 pages) | Cited 2 times

Online Publication Date: 1 April 2008

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By the study of a series of molecular liquids of fragilities covering almost the entire known range by the mechanical spectroscopy of quantitatively monitoring the healing of stress-induced microcracks recently developed by W. H. Wu et al. [Appl. Phys. Lett. 92, 011918 (2008)] , we show that the cracking healing temperature coincides with the onset glass temperature Tg, quite independent of the liquid fragility. Another interesting observation is that the major part of the modulus recovery occurs below Tg. Thus, our study establishes an additional approach to the study of the glass dynamics and glass transition which lends itself to a variety of potential applications.
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64.70.P- Glass transitions of specific systems
61.43.Fs Glasses
62.20.mt Cracks

Domain mapping of a Ca-doped manganite

Joshua J. Turner, Jean L. Jordan-Sweet, Mary Upton, John P. Hill, Yoshinori Tokura, Yasuhide Tomioka, and Stephen D. Kevan

Appl. Phys. Lett. 92, 131907 (2008); http://dx.doi.org/10.1063/1.2905283 (3 pages) | Cited 1 time

Online Publication Date: 2 April 2008

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We have performed microdiffraction experiments to map the crystallographic domain structure of the Ca-doped manganite Pr0.5Ca0.5MnO3 by microfocusing x-rays through a glass capillary. Domain structure on the order of a few microns is observed. We suggest that this finding implies that the crystallographic domains maybe relevant to the phenomenon of phase separation—such twin boundaries could help determine the submicron size disorder that has been observed recently, and thus may ultimately play a role in colossal magnetoresistance.
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61.66.Fn Inorganic compounds
61.72.Mm Grain and twin boundaries

Intrinsic stress evolution in nanocrystalline diamond thin films with deposition temperature

X. Xiao, B. W. Sheldon, Y. Qi, and A. K. Kothari

Appl. Phys. Lett. 92, 131908 (2008); http://dx.doi.org/10.1063/1.2906903 (3 pages) | Cited 10 times

Online Publication Date: 2 April 2008

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The stress evolution in nanocrystalline diamond (NCD) films deposited at different temperatures (from 800 to 400 °C) was investigated. Results showed that the intrinsic stress gradually changed from tensile to compressive with decreasing deposition temperature. Most importantly, the intrinsic stress can be tailored to zero by adjusting the deposition temperature, which is critical to many applications. It has been proven that more H as well as sp2 bonded carbon was incorporated into the grain boundaries, which was responsible for the evolution of stress and other mechanical properties with deposition temperature. Moreover, all the NCD films showed excellent mechanical properties.
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62.25.-g Mechanical properties of nanoscale systems
68.60.Bs Mechanical and acoustical properties
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
61.72.Mm Grain and twin boundaries

Single impact crater functions for ion bombardment of silicon

N. Kalyanasundaram, M. Ghazisaeidi, J. B. Freund, and H. T. Johnson

Appl. Phys. Lett. 92, 131909 (2008); http://dx.doi.org/10.1063/1.2905297 (3 pages) | Cited 18 times

Online Publication Date: 3 April 2008

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The average effect of a single 500 eV incident argon ion on a silicon surface is studied using molecular dynamics simulations. More than 103 ion impacts at random surface points are averaged for each of seven incidence angles, from 0° to 28° off normal, to determine a local surface height change function, or a crater function. The crater shapes are mostly determined by mass rearrangement; sputtering has a relatively small effect. Analytical fitting functions are provided for several cases, and may serve as input into kinetic Monte Carlo calculations or stability analyses for surfaces subjected to ion bombardment.
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68.35.bg Semiconductors
68.47.Fg Semiconductor surfaces
61.82.Fk Semiconductors
61.80.Jh Ion radiation effects

On the dynamic fragmentation of laser shock-melted tin

T. de Rességuier, L. Signor, A. Dragon, M. Boustie, and L. Berthe

Appl. Phys. Lett. 92, 131910 (2008); http://dx.doi.org/10.1063/1.2906907 (3 pages) | Cited 6 times

Online Publication Date: 3 April 2008

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Dynamic fragmentation in liquid metals is an issue of increasing interest in shock physics, both for basic and applied scientific motivations. In a recent paper, we have reported an exploratory study of liquid spall in tin samples melted upon laser-driven shocks. The need for further experiments and analyses to answer some questions raised by that work had been pointed out. Thus, we present here some complementary results, including specific recovery tests as well as high speed transverse shadowgraphy to visualize both the expanding cloud of fast droplets and the late motion of large fragments that had been inferred from postshock observations.
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61.25.Mv Liquid metals and alloys
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
62.50.Ef Shock wave effects in solids and liquids

Merging of the α and β relaxations and aging via the Johari–Goldstein modes in rapidly quenched metallic glasses

Jörg Hachenberg, Dennis Bedorf, Konrad Samwer, Ranko Richert, Annelen Kahl, Marios D. Demetriou, and William L. Johnson

Appl. Phys. Lett. 92, 131911 (2008); http://dx.doi.org/10.1063/1.2903697 (3 pages) | Cited 16 times

Online Publication Date: 4 April 2008

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This paper provides evidence that the physical aging of deeply and rapidly quenched metallic glasses is promoted by the Johari–Goldstein slow β relaxation, resulting in a significant irreversible increase in the mechanical modulus on initial heating. Dynamic mechanical analysis has been used to characterize relaxation phenomena of a strong and a fragile metallic glass. In addition, we can extrapolate the temperature dependence of β- and α-relaxation peaks to higher temperatures and calculate the merging temperature for both types of glasses.
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61.43.Fs Glasses
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
62.20.de Elastic moduli
81.40.Jj Elasticity and anelasticity, stress-strain relations

Photoluminescence from highly excited AlN epitaxial layers

Yoichi Yamada, Kihyun Choi, Seungho Shin, Hideaki Murotani, Tsunemasa Taguchi, Narihito Okada, and Hiroshi Amano

Appl. Phys. Lett. 92, 131912 (2008); http://dx.doi.org/10.1063/1.2906894 (3 pages) | Cited 13 times

Online Publication Date: 4 April 2008

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Excitonic optical properties of AlN epitaxial layers have been studied by means of photoluminescence and optical reflectance spectroscopies. The binding energy of free excitons was estimated to be 57 meV on the basis of the energy separation between the n = 1 ground and n = 2 excited states. In addition, the luminescence line due to radiative recombination of biexcitons was observed under high density excitation. The energy separation between free-exciton luminescence and biexciton luminescence was 19 meV, which corresponded to the binding energy of biexcitons. Therefore, the ratio of the biexciton binding energy to the exciton binding energy was approximately 0.33.
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71.35.-y Excitons and related phenomena
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
68.55.-a Thin film structure and morphology

Effect of chain length on low temperature gold-gold bonding by self-assembled monolayers

X. F. Ang, Z. Chen, C. C. Wong, and J. Wei

Appl. Phys. Lett. 92, 131913 (2008); http://dx.doi.org/10.1063/1.2906905 (3 pages) | Cited 3 times

Online Publication Date: 4 April 2008

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The tensile strength of thermocompression gold joints formed with prior surface coatings of alkanethiol self-assembled monolayers (SAMs) depends on the chain length (n) of the SAM. Enhancement of bond strength is most significant at n = 6 while no improvement can be achieved using octadecanethiol (n = 18). These contrasting behaviors can be interpreted as a consequence of two dominant roles of alkanethiols that govern the bonding phenomenon, namely, the passivation of gold surfaces and the ease of mechanical and/or thermal displacement.
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68.35.Gy Mechanical properties; surface strains
81.65.Rv Passivation
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.20.Vj Joining; welding

Theoretical and experimental depth-resolved cathodoluminescence microanalysis of excitonic emission from ZnO epilayers

J. D. Ye, H. Zhao, W. Liu, S. L. Gu, R. Zhang, Y. D. Zheng, S. T. Tan, X. W. Sun, G. Q. Lo, and K. L. Teo

Appl. Phys. Lett. 92, 131914 (2008); http://dx.doi.org/10.1063/1.2907249 (3 pages) | Cited 2 times

Online Publication Date: 4 April 2008

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In this letter, the excitonic emissions from ZnO epilayers were studied by depth-resolved cathodoluminescence (CL) microanalysis. An excellent agreement between the redshift of the experimental depth-resolved CL emission and theoretically simulated values was observed, which clearly identified its origin to be the strong internal absorption in ZnO epilayer. Moreover, the rigorous Monte Carlo simulated CL generation profiles with the correction of self-absorption exhibit the reasonable correspondence with the measured CL intensities. The intensity discrepancies for low and high excitation cases have been interpreted by the occurrence of the excess carrier nonradiative recombination on the surface space charge layer and the exciton nonradiative quenching processing by defects or structural disorders near the interface of ZnO and sapphire.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Hf II-VI semiconductors
68.55.ag Semiconductors
71.35.-y Excitons and related phenomena
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
82.80.-d Chemical analysis and related physical methods of analysis
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Temperature dependence of the phase-coherence length in InN nanowires

Ch. Blömers, Th. Schäpers, T. Richter, R. Calarco, H. Lüth, and M. Marso

Appl. Phys. Lett. 92, 132101 (2008); http://dx.doi.org/10.1063/1.2905268 (3 pages) | Cited 11 times

Online Publication Date: 31 March 2008

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We report on low-temperature magnetotransport measurements on InN nanowires, grown by plasma-assisted molecular beam epitaxy. The characteristic fluctuation pattern observed in the conductance was employed to obtain information on phase-coherent transport. By analyzing the root mean square and the correlation field of the conductance fluctuations at various temperatures, the phase-coherence length was determined.
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72.20.My Galvanomagnetic and other magnetotransport effects
73.63.Nm Quantum wires

On the identity of a crucial defect contributing to leakage current in silicon particle detectors

J. H. Bleka, L. Murin, E. V. Monakhov, B. S. Avset, and B. G. Svensson

Appl. Phys. Lett. 92, 132102 (2008); http://dx.doi.org/10.1063/1.2896313 (3 pages) | Cited 5 times

Online Publication Date: 31 March 2008

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The annealing kinetics of the so-called E4/E5 center or E4a/E4b center in electron-irradiated Si particle detectors has been studied at four different temperatures from 23 to 65 °C using deep-level transient spectroscopy (DLTS). The center gives rise to two energy levels at 0.37 and 0.45 eV below the conduction-band edge, and the annealing process is found to be of dissociative nature with an energy barrier of 1.1–1.2 eV. A striking similarity of the annealing rates (and kinetics) is revealed with that obtained for the 936-cm−1 infrared absorption band, studied by Fourier-transform infrared spectroscopy using identical type of Si material as in the DLTS study but irradiated with neutrons. The result strongly suggest that the E4/E5 levels and the 936-cm−1 band originate from the same defect, and the latter has been attributed to a di-interstitial-oxygen (I2O) complex. The E4/E5 center plays a crucial role for the detrimental leakage current in irradiated Si particle detectors, and an assignment of E4/E5 to I2O implies that oxygen-lean Si material (<1014 cm−3) should be advantageous to enhance detector performance.
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61.82.Fk Semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters

Correlation between microstructure, electronic properties and flicker noise in organic thin film transistors

Oana D. Jurchescu, Behrang H. Hamadani, Hao D. Xiong, Sungkyu K. Park, Sankar Subramanian, Neil M. Zimmerman, John E. Anthony, Thomas N. Jackson, and David J. Gundlach

Appl. Phys. Lett. 92, 132103 (2008); http://dx.doi.org/10.1063/1.2903508 (3 pages) | Cited 21 times

Online Publication Date: 31 March 2008

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We report on observations of a correlation between the microstructure of organic thin films and their electronic properties when incorporated in field-effect transistors. We present a simple method to induce enhanced grain growth in solution-processed thin film transistors by chemical modification of the source-drain contacts. This leads to improved device performance and gives a unique thin film microstructure for fundamental studies concerning the effect of structural order on the charge transport. We demonstrate that the 1/f flicker noise is sensitive to organic semiconductor thin film microstructure changes in the transistor channel.
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85.30.Tv Field effect devices

Analysis of electronic memory traps in the oxide-nitride-oxide structure of a polysilicon-oxide-nitride-oxide-semiconductor flash memory

Y. J. Seo, K. C. Kim, T. G. Kim, Y. M. Sung, H. Y. Cho, M. S. Joo, and S. H. Pyi

Appl. Phys. Lett. 92, 132104 (2008); http://dx.doi.org/10.1063/1.2830000 (3 pages) | Cited 13 times

Online Publication Date: 31 March 2008

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The origin of the electron memory trap in an oxide-nitride-oxide structure deposited on n-type Si is investigated by both capacitance-voltage and deep level transient spectroscopy (DLTS). Two electron traps are observed near 0.27 and 0.54 eV, below the conduction band minimum of Si and are identified as the nitride bulk trap and the Si–SiO2 interfacial trap, respectively. The trap depth, viz., vertical distribution of the electron trap, in both nitride bulk and Si–SiO2 interface, are also estimated from the bias voltage dependent DLTS.
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84.30.Sk Pulse and digital circuits

Enhancement of upconversion luminescence of Er doped Al2O3 films by Ag island films

Takeho Aisaka, Minoru Fujii, and Shinji Hayashi

Appl. Phys. Lett. 92, 132105 (2008); http://dx.doi.org/10.1063/1.2896303 (3 pages) | Cited 32 times

Online Publication Date: 1 April 2008

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Strong enhancement of upconversion photoluminescence (PL) of Er3+ in the visible range was achieved by placing it near rough Ag island films. In order to understand the mechanism of the enhancement, PL was excited by 978 and 488 nm light and the enhancement factors were obtained in a wide spectral range (520 nm to 1.6 μm). The emission and excitation wavelength dependence of the enhancement factors revealed that both the incident electric fields and the radiative decay rate of Er3+ are enhanced due to the excitation of surface plasmons supported by Ag islands. It was found that the upconversion PL is more sensitive to the enhancement of the incident electric field than the downconversion PL because of the multiphoton absorption process. The present result indicates that the upconversion PL obtains more benefit from the metal-enhanced fluorescence technique than the downconversion PL.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.66.Nk Insulators
78.55.Hx Other solid inorganic materials
78.40.Ha Other nonmetallic inorganics

Determination of spin polarization in InAs/GaAs self-assembled quantum dots

F. G. G. Hernandez, T. P. Mayer Alegre, and G. Medeiros-Ribeiro

Appl. Phys. Lett. 92, 132106 (2008); http://dx.doi.org/10.1063/1.2905809 (3 pages) | Cited 2 times

Online Publication Date: 1 April 2008

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The spin polarization of electrons trapped in InAs self-assembled quantum dot ensembles is investigated. A statistical approach for the population of the spin levels allows one to infer the spin polarization from the measured values of the addition energies. From the magnetocapacitance spectroscopy data, the authors found a fully polarized ensemble of electronic spins above 10 T when B∥[001] and at 2.8 K. Finally, by including the g-tensor anisotropy, the angular dependence of the spin polarization with the magnetic field B orientation and strength could be determined.
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72.25.-b Spin polarized transport
73.21.La Quantum dots
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
75.30.Gw Magnetic anisotropy

High quality anatase TiO2 film: Field-effect transistor based on anatase TiO2

Masao Katayama, Shinya Ikesaka, Jun Kuwano, Hideomi Koinuma, and Yuji Matsumoto

Appl. Phys. Lett. 92, 132107 (2008); http://dx.doi.org/10.1063/1.2906361 (3 pages) | Cited 12 times

Online Publication Date: 2 April 2008

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We proposed an oxygen modulation method for the growth of high crystalline and insulative anatase films. The cycle of deposition under low oxygen pressure and annealing under high oxygen pressure was repeated every 1 nm thick growth. The sharp reflection high-energy electron diffraction pattern and step-and-terrace surface morphology confirmed high crystallinity of the obtained anatase film; the resistivity reached as high as 1.8 MΩ cm. As a result, the present anatase film exhibited high performance in a field-effect transistor as an active channel. On-to-off current ratio and field-effect mobility exceeded 105 and 0.3 cm2/V s, respectively.
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68.55.ag Semiconductors
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
68.35.bg Semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
73.61.Le Other inorganic semiconductors
85.30.Tv Field effect devices

Hole mobility in Mg-doped p-type InN films

Xinqiang Wang, Song-Bek Che, Yoshihiro Ishitani, and Akihiko Yoshikawa

Appl. Phys. Lett. 92, 132108 (2008); http://dx.doi.org/10.1063/1.2906374 (3 pages) | Cited 23 times

Online Publication Date: 2 April 2008

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Mg-doped p-type InN layers with different thicknesses were grown under the same growth/doping conditions so that their net acceptor concentrations were almost the same (3–6)×1018 cm−3, which were confirmed by electrolyte capacitance-voltage measurements. The conductivity of p-InN region embedded under high density surface electrons could be extracted through the slope of total sheet conductivity against thickness, which was about 8.1 Ω−1 cm−1. Then, corresponding hole mobility was determined to be about 17–36 cm2/V s for the hole concentrations of about (1.4–3.0)×1018 cm−3 obtained by providing the hole effective mass and Mg acceptor activation energy as 0.42m0 and 61 meV, respectively.
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72.20.Fr Low-field transport and mobility; piezoresistance
73.61.Ey III-V semiconductors
61.72.uj III-V and II-VI semiconductors
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Diffusion and thermal stability of hydrogen in ZnO

Junhyeok Bang and K. J. Chang

Appl. Phys. Lett. 92, 132109 (2008); http://dx.doi.org/10.1063/1.2906379 (3 pages) | Cited 30 times

Online Publication Date: 2 April 2008

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We perform both first-principles calculations and kinetic Monte Carlo (kMC) simulations to study the diffusion and thermal stability of hydrogen in ZnO. The migration energy of a substitutional hydrogen (HO) is 1.7 eV, much higher than the value of 0.4–0.5 eV for an interstitial hydrogen (Hi). Using as input the calculated energy barriers for H diffusion, kMC simulations show that while Hi diffuses out at low temperature, the thermal stability of HO is maintained up to 475 °C, in good agreement with the annealing data. In addition, our calculations suggest that injected hydrogen from air turns into HO, causing n-type conductivity.
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66.30.Dn Theory of diffusion and ionic conduction in solids
61.72.jj Interstitials
66.30.Lw Diffusion of other defects
72.80.Ey III-V and II-VI semiconductors

P-type semiconducting gas sensing behavior of nanoporous rf sputtered CaCu3Ti4O12 thin films

E. Joanni, R. Savu, P. R. Bueno, E. Longo, and J. A. Varela

Appl. Phys. Lett. 92, 132110 (2008); http://dx.doi.org/10.1063/1.2905810 (3 pages) | Cited 8 times

Online Publication Date: 4 April 2008

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The fabrication of nanoporous sputtered CaCu3Ti4O12 thin films with high gas sensitivity is reported in this work. The porous microstructure and the nanocrystalline nature of the material promoted the diffusion of the atmosphere into the film, shortening the response time of the samples. Behaving as p-type semiconductor, the material presents enhanced sensitivity even at low working temperatures. Impedance spectroscopy measurements were performed in order to investigate the mechanisms responsible for the performance of the devices.
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81.05.Rm Porous materials; granular materials
81.15.Cd Deposition by sputtering
68.55.ag Semiconductors
82.80.-d Chemical analysis and related physical methods of analysis
66.30.Pa Diffusion in nanoscale solids
61.43.Gt Powders, porous materials

Huge positive magnetoresistance in a gated AlGaAs/GaAs high electron mobility transistor structure at high temperatures

C.-T. Liang, Yen Shung Tseng, Jau-Yang Wu, Sheng-Di Lin, Chun-Kai Yang, Yu-Ru Li, Kuang Yao Chen, Po-Tsun Lin, and Li-Hung Lin

Appl. Phys. Lett. 92, 132111 (2008); http://dx.doi.org/10.1063/1.2906360 (3 pages)

Online Publication Date: 4 April 2008

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Magnetoresistivity measurements on a gated AlGaAs/GaAs high electron mobility transistor (HEMT) structure were performed at high temperatures T. By changing the applied gate voltage Vg, we can investigate the observed huge positive magnetoresistance (PMR) at different effective disorder and density inhomogeneity within the same HEMT structure. The observed PMR value increases with increasing disorder in the depletion mode (Vg ⩽ 0). Moreover, the PMR value is not limited by the quality of the HEMT structure at T = 80 K. Such results pave the way for low-cost, high-throughput GaAs-based HEMT fabrication for future magnetic sensing and recording devices fully compatible with the mature HEMT technology.
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85.30.Tv Field effect devices

Ordered n-type ZnO nanorod arrays

Huijuan Zhou, Johannes Fallert, Janos Sartor, Roman J. B. Dietz, Claus Klingshirn, Heinz Kalt, Daniel Weissenberger, Dagmar Gerthsen, Haibo Zeng, and Weiping Cai

Appl. Phys. Lett. 92, 132112 (2008); http://dx.doi.org/10.1063/1.2907197 (3 pages) | Cited 20 times

Online Publication Date: 4 April 2008

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Using indium as catalyst for growth and simultaneously as doping source, ordered arrays of n-type ZnO single crystal nanorods have been perpendicularly grown on p-GaN/Al2O3 substrates with a vapor phase transport growth method. The low temperature photoluminescence measurements of the n-ZnO nanorods show dominant In-related neutral donor bound exciton emission in the ultraviolet region. Electrical transport measurements performed on single n-ZnO nanorods yield resistances of about 50–200 kΩ and a typical specific resistivity of 2.0×10−2 Ω cm. The resistivity is one order of magnitude reduced by introducing In compared to the nominally undoped ZnO nanorods.
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81.16.-c Methods of micro- and nanofabrication and processing
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.55.Et II-VI semiconductors
73.63.-b Electronic transport in nanoscale materials and structures
73.22.Lp Collective excitations
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Effect of superconductivity on the electronic transport and capacitance of La1.85Sr0.15CuO4/Nb doped SrTiO3 heterojunction

J. P. Shi, Y. G. Zhao, H. J. Zhang, and X. P. Zhang

Appl. Phys. Lett. 92, 132501 (2008); http://dx.doi.org/10.1063/1.2904628 (3 pages) | Cited 5 times

Online Publication Date: 31 March 2008

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The authors report the effect of superconductivity on the electronic transport and capacitance of La1.85Sr0.15CuO4/Nb doped SrTiO3 heterojunction. This heterojunction shows good rectifying property. With the occurrence of superconductivity, the capacitance, junction resistance, and diffusion voltage of the heterojunction show jumps, which correlate with the resistance change of La1.85Sr0.15CuO4. Analysis shows that the current-voltage behavior of the heterojunction is consistent with that of the inhomogeneous Schottky contacts. The results were discussed by considering the effect of superconductivity on the inhomogeneous heterojunction. This work is helpful for the understanding of superconductor based heterojunctions and inhomogeneous Schottky contacts.
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74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
73.30.+y Surface double layers, Schottky barriers, and work functions

Two-dimensional vortex-pinning phenomena in YBa2Cu3Oy films

S. Horii, M. Takamura, M. Mukaida, A. Ichinose, K. Yamada, R. Teranishi, K. Matsumoto, R. Kita, Y. Yoshida, J. Shimoyama, and K. Kishio

Appl. Phys. Lett. 92, 132502 (2008); http://dx.doi.org/10.1063/1.2905263 (3 pages) | Cited 9 times

Online Publication Date: 1 April 2008

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Anomalous superconducting properties were demonstrated in anisotropic high-critical-temperature superconductors (HTSCs) by simultaneously introducing two different planar types of vortex-pinning centers. The nanostructure, magnetic field, and field-angle dependency of critical current properties for an a-axis-grown multilayered film consisting of superconducting and semiconducting layers were characterized. Semiconductive layers running perpendicular to CuO2 superconducting layers behave as novel two-dimensional vortex-pinning centers that reverse the typical magnetic response in the superconducting state observed for conventional HTSCs. The results indicate that the vortex behavior in nanostructured HTSCs can be controlled; therefore, significant potential exists for further improvement of the critical current properties.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
74.78.Na Mesoscopic and nanoscale systems
74.25.Sv Critical currents

Anomalous magnetic ordering in b-axis-oriented orthorhombic HoMnO3 thin films

T. H. Lin, C. C. Hsieh, H. C. Shih, C. W. Luo, T. M. Uen, K. H. Wu, J. Y. Juang, J.-Y. Lin, C.-H. Hsu, and S. J. Liu

Appl. Phys. Lett. 92, 132503 (2008); http://dx.doi.org/10.1063/1.2904649 (3 pages) | Cited 14 times

Online Publication Date: 1 April 2008

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Orthorhombic HoMnO3 films with well-aligned crystallographic orientations were deposited on LaAlO3(110) single crystal substrates by using pulsed laser deposition. The nearly perfect b-axis-oriented films provide the opportunity of investigating the orientation-dependent physical property of this material. The temperature dependent magnetization evidently displays an antiferromagnetic ordering near 42 K, irrespective to the direction of applied field. Furthermore, the theoretically expected lock-in transition was clearly observed at around 30 K when field was applied along the c axis and was undetectable along the a and b axes. The 30 K transition was suppressed to 26 K when the applied field increased from 100 to 500 Oe.
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75.70.Ak Magnetic properties of monolayers and thin films
68.55.J- Morphology of films
81.15.Fg Pulsed laser ablation deposition
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Ee Antiferromagnetics

Partial frequency band gap in one-dimensional magnonic crystals

M. Kostylev, P. Schrader, R. L. Stamps, G. Gubbiotti, G. Carlotti, A. O. Adeyeye, S. Goolaup, and N. Singh

Appl. Phys. Lett. 92, 132504 (2008); http://dx.doi.org/10.1063/1.2904697 (3 pages) | Cited 33 times

Online Publication Date: 1 April 2008

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Collective spin wave modes propagating in an array of magnetic stripes coupled by dynamic dipole interaction are investigated by Brillouin light scattering. It is demonstrated that this structure supports propagation of discrete spin waves at any angle with respect to the stripes length. The data are interpreted using a theoretical model based on the Bloch wave approach. It is shown that, due to the one-dimensional artificial periodicity of the medium, the gaps in the spin wave spectrum are partial: the frequency passbands for propagation along the direction of periodicity overlap with the stop bands for propagation along the stripes.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.35.+c Brillouin and Rayleigh scattering; other light scattering
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
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