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31 May 2010

Volume 96, Issue 22, Articles (22xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 96, 223101 (2010); http://dx.doi.org/10.1063/1.3439728 (3 pages)

Seokho Yun, Jeremy A. Bossard, Theresa S. Mayer, and Douglas H. Werner
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Morphology characterization of argon-mediated epitaxial graphene on C-face SiC

J. L. Tedesco, G. G. Jernigan, J. C. Culbertson, J. K. Hite, Y. Yang, K. M. Daniels, R. L. Myers-Ward, C. R. Eddy, J. A. Robinson, K. A. Trumbull, M. T. Wetherington, P. M. Campbell, and D. K. Gaskill

Appl. Phys. Lett. 96, 222103 (2010); http://dx.doi.org/10.1063/1.3442903 (3 pages) | Cited 17 times

Online Publication Date: 1 June 2010

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Epitaxial graphene layers were grown on the C-face of 4H–SiC and 6H–SiC using an argon-mediated growth process. Variations in growth temperature and pressure were found to dramatically affect the morphological properties of the layers. The presence of argon during growth slowed the rate of graphene formation on the C-face and led to the observation of islanding. The similarity in the morphology of the islands and continuous films indicated that island nucleation and coalescence is the growth mechanism for C-face graphene.
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81.05.ue Graphene
68.55.-a Thin film structure and morphology
68.55.J- Morphology of films
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth

Enhanced conductivity of tunnel junctions employing semimetallic nanoparticles through variation in growth temperature and deposition

Hari P. Nair, Adam M. Crook, and Seth R. Bank

Appl. Phys. Lett. 96, 222104 (2010); http://dx.doi.org/10.1063/1.3442909 (3 pages) | Cited 5 times

Online Publication Date: 1 June 2010

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We report ErAs nanoparticle-enhanced tunnel junctions grown on GaAs with low specific resistances (<2×10−4 Ω cm−2), approximately tenfold lower than previous reports. A reduction in specific resistance was achieved by modifying the ErAs nanoparticle morphology through the molecular beam epitaxial growth conditions, particularly lower growth temperatures. A further investigation of the variation in tunnel junction resistance with the amount of ErAs deposited and growth temperature shows that nanoparticle surface coverage may not be the only factor determining tunnel junction resistance.
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61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
68.55.A- Nucleation and growth
73.61.At Metal and metallic alloys
68.35.B- Structure of clean surfaces (and surface reconstruction)

Self-confined GaN heterophased quantum wells

Ikai Lo, Yu-Chi Hsu, Chia-Ho Hsieh, Wen-Yuan Pang, Mitch M. C. Chou, Yen-Liang Chen, Cheng-Hung Shih, and Ying-Chieh Wang

Appl. Phys. Lett. 96, 222105 (2010); http://dx.doi.org/10.1063/1.3442497 (3 pages)

Online Publication Date: 2 June 2010

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Wurtzite/zinc-blende/wurtzite GaN heterophased quantum wells (QWs) were grown by plasma-assisted molecular beam epitaxy. A self-assembling mechanism was used to simulate the heterophased QW, in which a wurtzite/zinc-blende phase transition was created by rotating the threefold symmetric N-Ga vertical bond 60°. The GaN heterophased QW was attested by transmission electron microscopy, selective area electron diffraction and cathodoluminescence measurements.
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81.07.St Quantum wells
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
78.67.De Quantum wells
78.60.Hk Cathodoluminescence, ionoluminescence
68.55.ag Semiconductors

Band structure measurement of organic single crystal with angle-resolved photoemission

Huanjun Ding, Colin Reese, Antti J. Mäkinen, Zhenan Bao, and Yongli Gao

Appl. Phys. Lett. 96, 222106 (2010); http://dx.doi.org/10.1063/1.3446849 (3 pages) | Cited 8 times

Online Publication Date: 3 June 2010

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The electronic structure of bulk rubrene single crystal was studied with angle-resolved photoemission spectroscopy. Highly reproducible dispersive features were observed with nice symmetry about the Brillouin zone center and boundaries, representing the band structure measured for a bulk organic single crystal. The high quality of the surface was confirmed with scanning tunneling microscopy. The energy dispersion of the highest occupied molecular orbitals derived bands showed strong anisotropic behavior in the a-b plane of the unit cell. The measured band structure, however, differs unexpectedly from theoretical calculations in terms of the amount of the dispersion and the separation of the bands.
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71.20.Rv Polymers and organic compounds
79.60.Fr Polymers; organic compounds

Quantum confinement effects in Si/Ge heterostructures with spatially ordered arrays of self-assembled quantum dots

Oleksiy B. Agafonov, Christian Dais, Detlev Grützmacher, and Rolf J. Haug

Appl. Phys. Lett. 96, 222107 (2010); http://dx.doi.org/10.1063/1.3442508 (3 pages) | Cited 2 times

Online Publication Date: 3 June 2010

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Magnetotunneling spectroscopy was employed to probe the confinement in vertical Si/Ge double-barrier resonant tunneling diodes with regularly distributed Ge quantum dots. Their current-voltage characteristics reveal a steplike behavior in the vicinity of zero bias, indicating resonant tunneling of heavy-holes via three-dimensionally confined unoccupied hole states in Ge quantum dots. Assuming parabolic confinement, we extract the strength of the confinement potential of quantum dots.
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78.20.Ls Magneto-optical effects
73.21.La Quantum dots
75.75.Lf Electronic structure of magnetic nanoparticles
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.16.Dn Self-assembly
73.40.Jn Metal-to-metal contacts

Improvement of resistance switching characteristics in a thin FeOx transition layer of TiN/SiO2/FeOx/FePt structure by rapid annealing

Li-Wei Feng, Chun-Yen Chang, Yao-Feng Chang, Ting-Chang Chang, Shin-Yuan Wang, Shih-Ching Chen, Chao-Cheng Lin, Shih-Cheng Chen, and Pei-Wei Chiang

Appl. Phys. Lett. 96, 222108 (2010); http://dx.doi.org/10.1063/1.3428777 (3 pages) | Cited 5 times

Online Publication Date: 3 June 2010

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In this paper, the influence of a 600 °C rapid thermal annealing for 60 s on the improvements of resistance switching behaviors in a TiN/SiO2/FeOx/FePt structure is reported. It is found that besides the distinct reduction in memory switching parameters in forming voltage, set/reset voltages, and their dispersions, the resistance ratio of high-resistance state to low-resistance state is also enlarged after annealing. The effects of annealing on improving the resistance switching properties are discussed by x-ray diffraction and x-ray photon-emission spectra depth profile results. Additionally, good retention characteristics are exhibited in the annealed TiN/SiO2/FeOx/FePt resistance switching memory.
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84.30.Sk Pulse and digital circuits

Silicon surface passivation by an organic overlayer of 9,10-phenanthrenequinone

Sushobhan Avasthi, Yabing Qi, Grigory K. Vertelov, Jeffrey Schwartz, Antoine Kahn, and James C. Sturm

Appl. Phys. Lett. 96, 222109 (2010); http://dx.doi.org/10.1063/1.3429585 (3 pages) | Cited 8 times

Online Publication Date: 4 June 2010

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Merged organic-silicon heterojunction devices require the passivation of dangling bonds at the silicon surface, preferably with a low-temperature process. In this paper, we demonstrate the high-quality passivation of the silicon (100) surface using an organic molecule (9,10-phenanthrenequinone, PQ). PQ reacts with the dangling bonds, thus providing a bridge between organic semiconductors and silicon. We measure low recombination velocities ( ∼ 150 cm/s) at the PQ-silicon interface. Metal/organic-insulator/silicon capacitors and transistors prove that at PQ-silicon interface, the Fermi level can be modulated. The formation of an inversion layer with electron mobility of 600 cm2/V∙s further demonstrates the passivation quality of PQ.
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81.65.Rv Passivation
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
84.32.Tt Capacitors

Influence of the oxidizing species on the Ge dangling bonds at the (100)Ge/GeO2 interface

Silvia Baldovino, Alessandro Molle, and Marco Fanciulli

Appl. Phys. Lett. 96, 222110 (2010); http://dx.doi.org/10.1063/1.3446839 (3 pages) | Cited 10 times

Online Publication Date: 4 June 2010

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The nature of the defects present at various Ge/GeO2 interfaces has been investigated by means of electrically detected magnetic resonance (EDMR) spectroscopy. GeO2 thin films were grown by atomic oxygen, ozone, and molecular oxygen exposure. The defect microstructure is sensitive to the oxidizing species, i.e., to the oxidation mechanism. Different EDMR spectra are correlated with the specific electrical response of the corresponding Ge/GeO2 metal-oxide-semiconductor structures.
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68.35.Ct Interface structure and roughness
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Extremely low drift of resistance and threshold voltage in amorphous phase change nanowire devices

Mukut Mitra, Yeonwoong Jung, Daniel S. Gianola, and Ritesh Agarwal

Appl. Phys. Lett. 96, 222111 (2010); http://dx.doi.org/10.1063/1.3447941 (3 pages) | Cited 16 times

Online Publication Date: 4 June 2010

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Time-dependent drift of resistance and threshold voltage in phase change memory (PCM) devices is of concern as it leads to data loss. Electrical drift in amorphous chalcogenides has been argued to be either due to electronic or stress relaxation mechanisms. Here we show that drift in amorphized Ge2Sb2Te5 nanowires with exposed surfaces is extremely low in comparison to thin-film devices. However, drift in stressed nanowires embedded under dielectric films is comparable to thin-films. Our results shows that drift in PCM is due to stress relaxation and will help in understanding and controlling drift in PCM devices.
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85.30.-z Semiconductor devices
85.35.-p Nanoelectronic devices
84.30.Sk Pulse and digital circuits
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Enhanced low field magnetoresistance in nanocrystalline La0.7Sr0.3MnO3 synthesized on MgO nanowires

Z. Zhang, R. Ranjith, B. T. Xie, L. You, L. M. Wong, S. J. Wang, J. L. Wang, W. Prellier, Y. G. Zhao, and T. Wu

Appl. Phys. Lett. 96, 222501 (2010); http://dx.doi.org/10.1063/1.3432113 (3 pages) | Cited 13 times

Online Publication Date: 1 June 2010

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We report on the structure and transport properties of nanocrystalline manganite La0.7Sr0.3MnO3 (LSMO) synthesized on nanowires-engineered MgO substrates by pulsed laser deposition, which is compared with reference samples deposited directly on flat MgO substrates. Such LSMO/MgO nanocomposites show enhanced low field magnetoresistance, especially at low temperature, due to the dominant spin-polarized intergrain tunneling. This work suggests that growing on nanoengineered substrates is a viable route to achieve nanostructured materials with desired crystalline structure and physical properties.
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72.20.My Galvanomagnetic and other magnetotransport effects
81.15.Fg Pulsed laser ablation deposition
61.46.Np Structure of nanotubes (hollow nanowires)

Controlled domain-wall injection in perpendicularly magnetized strips

R. Lavrijsen, J. H. Franken, J. T. Kohlhepp, H. J. M. Swagten, and B. Koopmans

Appl. Phys. Lett. 96, 222502 (2010); http://dx.doi.org/10.1063/1.3432703 (3 pages) | Cited 8 times

Online Publication Date: 1 June 2010

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For applications of domain wall (DW) motion in magnetic devices, it is vital to control the creation and position of the DW. We use Ga+ irradiation of Pt/Co/Pt strips to locally change the perpendicular magnetic anisotropy. This allows us to controllably inject DWs into a device at a tunable field. The observed initial linear decrease and subsequent increase in the DW injection field upon increasing irradiation dose are explained by micromagnetic simulations and an analytical one-dimensional model.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ch Domain walls and domain structure
75.30.Gw Magnetic anisotropy
75.78.Cd Micromagnetic simulations

Enhanced exchange anisotropy in IrMn/CoFeB systems and its correlation with uncompensated interfacial spins

Yuqing Du, Genhua Pan, Roy Moate, Hendrik Ohldag, Andras Kovacs, and Amit Kohn

Appl. Phys. Lett. 96, 222503 (2010); http://dx.doi.org/10.1063/1.3442480 (3 pages) | Cited 6 times

Online Publication Date: 1 June 2010

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Bottom pinned exchange bias systems of IrMn/CoFe and IrMn/CoFeB on CoFe seed layers were studied. Enhanced exchange anisotropy has been observed for IrMn/CoFeB samples annealed at 350 °C. The ferromagnetic and antiferromagnetic layers of both samples are polycrystalline and textured {110} for the CoFe and CoFeB, and {111} for IrMn. Results demonstrated that the enhanced exchange anisotropy in the IrMn/CoFeB system is closely associated with the increased uncompensated interfacial spins as evidenced by the enhanced Mn x-ray magnetic circular dichroism (XMCD) signal strength. A quantitative correlation between the Mn XMCD signal and the exchange anisotropy constant Jk was observed.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
78.20.Ls Magneto-optical effects
81.40.Gh Other heat and thermomechanical treatments
75.50.Ee Antiferromagnetics
75.30.Gw Magnetic anisotropy

Electric field effect on magnetization at the Fe/MgO(001) interface

Manish K. Niranjan, Chun-Gang Duan, Sitaram S. Jaswal, and Evgeny Y. Tsymbal

Appl. Phys. Lett. 96, 222504 (2010); http://dx.doi.org/10.1063/1.3443658 (3 pages) | Cited 28 times

Online Publication Date: 2 June 2010

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Density-functional calculations are performed to explore magnetoelectric effects originating from the influence of an external electric field on magnetic properties of the Fe/MgO(001) interface. It is shown that the effect on the interface magnetization and magnetocrystalline anisotropy can be substantially enhanced if the electric field is applied across a dielectric material with a large dielectric constant. In particular, we predict an enhancement of the interface magnetoelectric susceptibility by a factor of the dielectric constant of MgO over that of the free standing Fe (001) surface. We also predict a significant effect of electric field on the interface magnetocrystalline anisotropy due to the change in the relative occupancy of the 3d-orbitals of Fe atoms at the Fe/MgO interface. These results may be interesting for technological applications such as electrically controlled magnetic data storage.
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75.85.+t Magnetoelectric effects, multiferroics
77.22.Ch Permittivity (dielectric function)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy

Emergence of ferromagnetism in antiferromagnetic TbMnO3 by epitaxial strain

X. Marti, V. Skumryev, C. Ferrater, M. V. García-Cuenca, M. Varela, F. Sánchez, and J. Fontcuberta

Appl. Phys. Lett. 96, 222505 (2010); http://dx.doi.org/10.1063/1.3443714 (3 pages) | Cited 12 times

Online Publication Date: 2 June 2010

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We show that in oxide thin films of spiral antiferromagnetic orthorhombic TbMnO3, ferromagnetism emerges resulting from epitaxially induced strain. The unit cell volume can be tuned (contracting up to a 2%) by varying thickness and deposition conditions; it is found that the ferromagnetic response correlates with the unit cell deformation. Such effect of strain on the magnetic properties turns out to be similar to that occurring in collinear orthorhombic antiferromagnets such as YMnO3. Owing to the intimate relationship between magnetic order and ferroelectricity in TbMnO3 these results may provide a new route to induce magnetoelectric coupling and tailor their ferroelectric response.
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75.70.Ak Magnetic properties of monolayers and thin films
68.60.Bs Mechanical and acoustical properties
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Ee Antiferromagnetics

Determining magnetic nanoparticle size distributions from thermomagnetic measurements

R. S. DiPietro, H. G. Johnson, S. P. Bennett, T. J. Nummy, L. H. Lewis, and D. Heiman

Appl. Phys. Lett. 96, 222506 (2010); http://dx.doi.org/10.1063/1.3441411 (3 pages) | Cited 6 times

Online Publication Date: 3 June 2010

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Thermomagnetic measurements are used to obtain the size distribution and anisotropy of magnetic nanoparticles. An analytical transformation method is described which utilizes temperature-dependent zero-field cooling magnetization data to provide a quantitative measurement of the average diameter and relative abundance of superparamagnetic nanoparticles. Applying this method to self-assembled MnAs nanoparticles in MnAs–GaAs composite films reveals a log-normal size distribution and reduced anisotropy for nanoparticles compared to bulk materials. This analytical technique holds promise for rapid assessment of the size distribution of an ensemble of superparamagnetic nanoparticles.
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61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
75.30.Gw Magnetic anisotropy
75.20.-g Diamagnetism, paramagnetism, and superparamagnetism

Magnetic properties and phase stability of L21 phase in Co2Mn(Ga1−xZx)(Z = Si, Ge, and Sn) Heusler alloys

A. Okubo, R. Y. Umetsu, K. Kobayashi, R. Kainuma, and K. Ishida

Appl. Phys. Lett. 96, 222507 (2010); http://dx.doi.org/10.1063/1.3427431 (3 pages) | Cited 6 times

Online Publication Date: 3 June 2010

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For the Co2Mn(Ga1−xZx) (Z = Si, Ge, and Sn) Heusler alloys, the L21/B2 order-disorder transition temperature TtL21/B2, the Curie temperature TC, and the saturation magnetization Ms were determined. The TtL21/B2 for all the systems linearly increases with increasing x. Although the TtL21/B2 was not determined in the high x region because of melting of alloys, those of Co2MnGe and Co2MnSn could be estimated by extrapolation from the quaternary data. The Ms at 4.2 K and the TC increase with x, and the Ms for all the systems is in good agreement with the Slater Pauling rule.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
64.70.K- Solid-solid transitions
64.60.Cn Order-disorder transformations
75.40.-s Critical-point effects, specific heats, short-range order

Control of magnetic and electric responses with electric and magnetic fields in magnetoelectric heterostructures

J. Das, M. Li, S. S. Kalarickal, S. Altmannshofer, K. S. Buchanan, J. F. Li, and D. Viehland

Appl. Phys. Lett. 96, 222508 (2010); http://dx.doi.org/10.1063/1.3443715 (3 pages) | Cited 8 times

Online Publication Date: 4 June 2010

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This paper reports on the tuning of both magnetic and electric responses with electric and magnetic fields for metglas-Pb (Zr,Ti)O3 based magnetoelectric (ME) heterostructures that can be promising for communication and sensor applications. The hysteresis loop results indicate a change in the in-plane magnetization due to application of voltages that leads to a tuning of the ferromagnetic resonance frequency by up to about 210 MHz with electric field. Furthermore, these structures show a high ME voltage coefficient that results in the detection of a 2 nT ac magnetic field and a low noise floor.
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75.85.+t Magnetoelectric effects, multiferroics
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

The origin of large overestimation of the magnetic entropy changes calculated directly by Maxwell relation

Weibin Cui, Wei Liu, and Zhidong Zhang

Appl. Phys. Lett. 96, 222509 (2010); http://dx.doi.org/10.1063/1.3446843 (3 pages) | Cited 9 times

Online Publication Date: 4 June 2010

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By investigating the nature of the first-order magnetostructural phase transition, we point out the origin of large overestimation of magnetic entropy changes calculated by directly applying the Maxwell relation. Furthermore, if the mass variations in ferromagnetic and paramagnetic phases on temperature are taken into consideration in two-phase region, taking MnAsCx, (Mn, Al)As, and Mn0.994Fe0.004As compounds as example, based on the modified Maxwell relation, the large overestimation and discrepancy of magnetic entropy changes disappear. The magnetic entropy changes are equivalent with the values by Clausius–Claperyon equation, indicating the validity of this modified approach.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.20.Ck Nonmetals
65.40.gd Entropy
64.70.K- Solid-solid transitions
75.50.Dd Nonmetallic ferromagnetic materials
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Kinetics of Ta ions penetration into porous low-k dielectrics under bias-temperature stress

Ming He, Ya Ou, Pei-I Wang, and Toh-Ming Lu

Appl. Phys. Lett. 96, 222901 (2010); http://dx.doi.org/10.1063/1.3442485 (3 pages) | Cited 4 times

Online Publication Date: 1 June 2010

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It is known that Ta, a popular diffusion barrier material, can itself penetrate into low-k dielectrics under bias-temperature stress. In this work, we derived a model which directly correlates the diffusivity of Ta ions to the rate of flatband voltage shift (FBS) of the Ta/methyl silsesquixane (MSQ)/Si capacitors. From our experimentally measured constant FBS rate, the Ta diffusivity and activation energy were determined. It appears that an increase in the porosity of MSQ film enhances the Ta diffusivity but does not affect the associated activation energy. This suggests the Ta ion diffusion is mainly through interconnected pore surfaces.
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84.32.Tt Capacitors

Improvement of memory performance by high temperature annealing of the Al2O3 blocking layer in a charge-trap type flash memory device

Jong Kyung Park, Youngmin Park, Sung Kyu Lim, Jae Sub Oh, Moon Sig Joo, Kwon Hong, and Byung Jin Cho

Appl. Phys. Lett. 96, 222902 (2010); http://dx.doi.org/10.1063/1.3442502 (3 pages) | Cited 6 times

Online Publication Date: 1 June 2010

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The effect of postdeposition annealing (PDA) of the Al2O3 blocking layer in a charge-trap type memory device is investigated. Significant improvements are achieved by high temperature PDA at 1100 °C, achieving faster operation speed, good charge retention, and a wide program/erase window. Experimental evidence shows that the underlying mechanism is not the changes in the band gap of the crystallized Al2O3 but is due to the higher trap density in the Si3N4 trapping layer at a deeper energy level by the intermixing between Al2O3 and Si3N4. The reduced trapping efficiency of the annealed Al2O3 also helps improve the retention property.
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84.30.Sk Pulse and digital circuits
61.72.Cc Kinetics of defect formation and annealing

Ferroelectric transition of Aurivillius compounds Bi5Ti3FeO15 and Bi6Ti3Fe2O18

J.-B. Li, Y. P. Huang, G. H. Rao, G. Y. Liu, J. Luo, J. R. Chen, and J. K. Liang

Appl. Phys. Lett. 96, 222903 (2010); http://dx.doi.org/10.1063/1.3447372 (3 pages) | Cited 11 times

Online Publication Date: 2 June 2010

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Single-phase Bi5Ti3FeO15 and Bi6Ti3Fe2O18 ceramics have been synthesized by solid state reaction. The ferroelectric transition of the compounds was studied by differential scanning calorimetry, high-temperature x-ray diffraction, and temperature-dependent dielectric measurements. Two solid-state structural transitions were observed in both compounds, one is the orthorhombic↔tetragonal transition (ferroelectric transition) at 1021 K for Bi5Ti3FeO15 and 973 K for Bi6Ti3Fe2O18, and the other is accompanied by an abrupt lattice expansion of the tetragonal phase at about 1110 K for Bi5Ti3FeO15 and about 1090 K for Bi6Ti3Fe2O18.
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87.85.J- Biomaterials
77.80.B- Phase transitions and Curie point

Ferroelectric Q-phase in a NaNbO3 epitaxial thin film

Yu. I. Yuzyuk, R. A. Shakhovoy, S. I. Raevskaya, I. P. Raevski, M. El Marssi, M. G. Karkut, and P. Simon

Appl. Phys. Lett. 96, 222904 (2010); http://dx.doi.org/10.1063/1.3437090 (3 pages) | Cited 6 times

Online Publication Date: 3 June 2010

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Epitaxial NaNbO3 thin films have been grown by pulsed laser deposition on cubic (00l) MgO substrate with epitaxial (La0.5Sr0.5)CoO3 buffer layer. Micro-Raman spectroscopy studies revealed that the ferroelectric Q phase (Pmc21, Z = 4) is stable in a 250-nm-thick film in contrast to the antiferroelectric phase P (Pbma, Z = 8) known to exist in the bulk single crystals and ceramics of undoped stoichiometric NaNbO3. Temperature-dependent Raman spectra indicate that the Q phase is stable over a wide temperature range (at least from 80 to 600 K), while the low-temperature ferroelectric rhombohedral phase N, typical for NaNbO3 single crystals, is not observed.
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77.80.-e Ferroelectricity and antiferroelectricity
77.55.fj Niobate- and tantalate-based films
78.30.Hv Other nonmetallic inorganics

Hierarchical domains in Na1/2Bi1/2TiO3 single crystals: Ferroelectric phase transformations within the geometrical restrictions of a ferroelastic inheritance

Jianjun Yao, Wenwei Ge, Liang Luo, Jiefang Li, D. Viehland, and Haosu Luo

Appl. Phys. Lett. 96, 222905 (2010); http://dx.doi.org/10.1063/1.3443717 (3 pages) | Cited 17 times

Online Publication Date: 3 June 2010

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We have found unique hierarchical domains in Na1/2Bi1/2TiO3 single crystals. A tetragonal ferroelastic domain structure is unchanged on cooling from 520 to 25 °C. Polar microdomains then nucleated on cooling in the rhombohedral ferroelectric phase within the geometrical restrictions imposed by the inherited ferroelastic domains.
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77.80.B- Phase transitions and Curie point
64.60.qj Studies of nucleation in specific substances
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.fg Shape-memory effect; yield stress; superelasticity

Electromechanical probing of ionic currents in energy storage materials

A. N. Morozovska, E. A. Eliseev, and S. V. Kalinin

Appl. Phys. Lett. 96, 222906 (2010); http://dx.doi.org/10.1063/1.3446838 (3 pages) | Cited 14 times

Online Publication Date: 4 June 2010

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The electrochemical processes in energy storage materials are generally linked with changes of molar volume of the host compound. Here, the frequency dependent strain response of one-dimensional electrochemically active system to periodic electric bias is analyzed. The sensitivity and resolution of electrochemical strain measurements are compared to the current-based electrochemical impedance spectroscopy. The resolution and detection limits of interferometric and atomic force microscopy based systems for probing electrochemical reactions on the nanoscale are analyzed.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)
81.16.Ta Atom manipulation
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Angle and polarization tolerant midinfrared dielectric filter designed by genetic algorithm optimization

Seokho Yun, Jeremy A. Bossard, Theresa S. Mayer, and Douglas H. Werner

Appl. Phys. Lett. 96, 223101 (2010); http://dx.doi.org/10.1063/1.3439728 (3 pages) | Cited 4 times

Online Publication Date: 1 June 2010

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We report a dielectric frequency selective surface filter with an angularly tolerant, polarization independent stop band designed at a midinfrared wavelength of 3.0 μm. The structure, consisting of a doubly-periodic amorphous silicon grating supported by a polyimide membrane, was optimized using a genetic algorithm to have a transmission stop band with a 3.33% 10 dB bandwidth for incidence angles as large as 10° from normal. The measured properties of the fabricated filter were within 1% of theoretical predictions. This strategy provides a practical and efficient approach to creating advanced dielectric filters for highly customized infrared optical device and coating applications.
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42.79.Ci Filters, zone plates, and polarizers
42.25.Ja Polarization
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