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28 Jun 2010

Volume 96, Issue 26, Articles (26xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 96, 261101 (2010); http://dx.doi.org/10.1063/1.3456618 (3 pages)

I. V. Konoplev, L. Fisher, A. W. Cross, A. D. R. Phelps, K. Ronald, and C. W. Robertson
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Evidence for surface states in a single 3 nm diameter Co3O4 nanowire

Yi Sun, Ji-Yong Yang, Rui Xu, Lin He, Rui-Fen Dou, and Jia-Cai Nie

Appl. Phys. Lett. 96, 262106 (2010); http://dx.doi.org/10.1063/1.3457449 (3 pages) | Cited 3 times

Online Publication Date: 29 June 2010

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The electronic local density of states of a single Co3O4 semiconductor nanowire with the diameter of 3 nm is explored using low-temperature scanning tunneling microscopy and spectroscopy. The energy gap between the conduction band and valence band of the nanowire is about 1.7 eV, which is slightly enhanced compared to the bulk value, ∼ 1.5 eV, due to the quantum confinement effect. Two surface states are observed locating near the Fermi level in the band gap.
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68.65.La Quantum wires (patterned in quantum wells)
81.07.Gf Nanowires
81.07.Vb Quantum wires
73.20.-r Electron states at surfaces and interfaces
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
71.20.-b Electron density of states and band structure of crystalline solids

Enhanced retention characteristic of NiSi2/SiNx compound nanocrystal memory

Jin Lu (闾锦), Ting-Chang Chang (張鼎張), Yu-Ting Chen (陳侑廷), Jheng-Jie Huang, Po-Chun Yang, Shih-Ching Chen, Hui-Chun Huang, Der-Shin Gan, New-Jin Ho, Yi Shi, and Ann-Kuo Chu

Appl. Phys. Lett. 96, 262107 (2010); http://dx.doi.org/10.1063/1.3457870 (3 pages) | Cited 5 times

Online Publication Date: 29 June 2010

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The NiSi2/SiNx compound nanocrystals (CNCs) were fabricated to integrate the compound tunnel barrier into nanocrystal memory, with the inclusion of nitride traps. The analysis of high resolution transmission electron microscopy and x-ray photoelectron spectroscopy reveal that the nanocrystal is mainly composed of NiSi2 and silicon nitride with small size of 4–5 nm and high density of ∼ 1×1012 cm−2. The charge storage characteristics of the memory capacitor based on NiSi2/SiNx CNCs were investigated by capacitance-voltage measurement and the enhanced retention characteristics, which remain 71.7% ( ∼ 1.9 V) in 104 s, are clarified to be due to the compound tunnel barrier and traps in nitride.
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84.32.Tt Capacitors
84.30.Sk Pulse and digital circuits
84.60.Ve Energy storage systems, including capacitor banks

Photoexcited charge current for the presence of pure spin current

Yu Liu, Yonghai Chen, and Zhanguo Wang

Appl. Phys. Lett. 96, 262108 (2010); http://dx.doi.org/10.1063/1.3455887 (3 pages) | Cited 1 time

Online Publication Date: 29 June 2010

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The asymmetric spin distribution in k space caused by the pure spin current (PSC) can introduce a photoexcited charge current (PECC). This provides us a practical scheme for direct detection of PSC. We demonstrate theoretically that the PECC related to the PSC depends sensitively on the wave vector and spin orientation of the carriers, more important, the helicity dependence of this PECC provides us a way to refine it from the helicity independent background current by tuning the polarized laser beams from left to right circular polarization.
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72.25.Dc Spin polarized transport in semiconductors

The influence of SiOx and SiNx passivation on the negative bias stability of Hf–In–Zn–O thin film transistors under illumination

Joon Seok Park, Tae Sang Kim, Kyoung Seok Son, Kwang-Hee Lee, Wan-Joo Maeng, Hyun-Suk Kim, Eok Su Kim, Kyung-Bae Park, Jong-Baek Seon, Woong Choi, Myung Kwan Ryu, and Sang Yoon Lee

Appl. Phys. Lett. 96, 262109 (2010); http://dx.doi.org/10.1063/1.3435482 (3 pages) | Cited 26 times

Online Publication Date: 29 June 2010

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The stability of hafnium indium zinc oxide thin film transistors under negative bias stress with simultaneous exposure to white light was evaluated. Two different inverted staggered bottom gate devices, each with a silicon oxide and a silicon nitride passivation, were compared. The latter exhibits higher field effect mobility but inferior subthreshold swing, and undergoes more severe shifts in threshold voltage (VT) during negative bias illumination stress. The time evolution of VT fits the stretched exponential equation, which implies that hydrogen incorporation during the nitride growth has generated bulk defects within the semiconductor and/or at the semiconductor/gate dielectric interface.
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85.30.Tv Field effect devices
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
81.05.-t Specific materials: fabrication, treatment, testing, and analysis
42.72.-g Optical sources and standards

Influence of electrode material on the resistive memory switching property of indium gallium zinc oxide thin films

Min-Chen Chen, Ting-Chang Chang, Chih-Tsung Tsai, Sheng-Yao Huang, Shih-Ching Chen, Chih-Wei Hu, Simon M. Sze, and Ming-Jinn Tsai

Appl. Phys. Lett. 96, 262110 (2010); http://dx.doi.org/10.1063/1.3456379 (3 pages) | Cited 30 times

Online Publication Date: 29 June 2010

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The InGaZnO taken as switching layer in resistive nonvolatile memory is proposed in this paper. The memory cells composed of Ti/InGaZnO/TiN reveal the bipolar switching behavior that keeps stable resistance ratio of 102 with switching responses over 100 cycles. The resistance switching is ascribed to the formation/disruption of conducting filaments upon electrochemical reaction near/at the bias-applied electrode. The influence of electrode material on resistance switching is investigated through Pt/InGaZnO/TiN devices, which perform the unipolar and bipolar behavior as applying bias on Pt and TiN electrode, respectively. Experimental results demonstrate that the switching behavior is selective by the electrode.
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85.30.Hi Surface barrier, boundary, and point contact devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Crystallographic orientation engineering in silicon-on-insulator substrates

T. Signamarcheix, B. Biasse, A.-M. Papon, E. Nolot, F. Mazen, J. Leveneur, O. Faynot, L. Clavelier, and B. Ghyselen

Appl. Phys. Lett. 96, 262111 (2010); http://dx.doi.org/10.1063/1.3459966 (3 pages) | Cited 2 times

Online Publication Date: 1 July 2010

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A bilayer silicon-on-insulator film was engineered to locally convert the crystallographic orientation from (100) to (110). The initial bilayer film is composed of a first 50 nm thick (110) oriented Si surface layer, above a second 20 nm thick (100) oriented Si underlayer. The bilayer film was elaborated using hydrophobic bonding to ensure an atomic contact between the two layers without any intermediate oxide. A local and deep-amorphization was developed by ion implantation to amorphize the (100) oriented Si underlayer, conserving also a partially crystalline (110) oriented surface layer. After such a deep amorphization, a solid phase epitaxy regrowth was performed at 900 °C. Transmission electron microscopy observations confirm that the partially crystalline surface layer acts as a seed for the epitaxial regrowth of the amorphized areas through the hydrophobic bonding interface. Thus, the orientation is locally converted from (100) to (110) in the underlayer, which could lead to the elaboration of hybrid films over a continuous insulating oxide that are mandatory for high performance electronic devices.
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68.55.ag Semiconductors
61.43.-j Disordered solids
68.55.J- Morphology of films

Direct-search deep level photothermal spectroscopy: An enhanced reliability method for overlapped semiconductor defect state characterization

Jun Xia and Andreas Mandelis

Appl. Phys. Lett. 96, 262112 (2010); http://dx.doi.org/10.1063/1.3458827 (3 pages) | Cited 1 time

Online Publication Date: 1 July 2010

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A method for resolving highly overlapped defects in rate-window analysis is proposed. This method offers high defect-state characterization reliability because it is based on direct multiparameter fitting of deep level photothermal spectra using combined temperature and frequency scans. Two direct search optimization algorithms are utilized as follows: the genetic algorithm for a search of possible solution areas and the pattern search algorithm for a refined search of global minimum. Four defect levels are identified using this technique.
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79.10.Ca Deep-level photothermal spectroscopy
07.60.-j Optical instruments and equipment

Different nonvolatile memory effects in epitaxial Pt/PbZr0.3Ti0.7O3/LSCO heterostructures

Jinsik Choi, Jin-Soo Kim, Inrok Hwang, Sahwan Hong, Ik-Su Byun, Seung-Woong Lee, Sung-Oong Kang, and Bae Ho Park

Appl. Phys. Lett. 96, 262113 (2010); http://dx.doi.org/10.1063/1.3460141 (3 pages) | Cited 5 times

Online Publication Date: 2 July 2010

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We found different nonvolatile memory effects between ferroelectric and resistive switching in Pt/PbZr0.3Ti0.7O3(PZT)/La0.5Sr0.5CoO3 (LSCO) heterostructures, depending on thickness of epitaxial PZT films. As the film thickness decreased below 34 nm, leakage and/or tunneling currents increased and hindered ferroelectric switching of films; alternatively, bipolar resistive switching was observed. Analysis using fitting plot on resistive switching behaviors suggested that variable Schottky barrier at the interface between Pt electrode and the film may be responsible for the different nonvolatile memory switching.
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85.50.Gk Non-volatile ferroelectric memories
73.30.+y Surface double layers, Schottky barriers, and work functions
84.30.Sk Pulse and digital circuits
77.80.Fm Switching phenomena

Control of transmission in disordered graphene nanojunctions through stochastic resonance

Luo-Luo Jiang, Liang Huang, Rui Yang, and Ying-Cheng Lai

Appl. Phys. Lett. 96, 262114 (2010); http://dx.doi.org/10.1063/1.3460291 (3 pages) | Cited 2 times

Online Publication Date: 2 July 2010

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We investigate electronic transport in graphene nanojunctions and find that the transmission (or the conductance) can exhibit a nonmonotonic behavior with respect to variation in the strength of disorder, mimicking a stochastic resonance. The general setting for this remarkable phenomenon is where the graphene device possesses localized states in the absence of disorder, i.e., the localized edge states specific to graphene. A small amount of disorder can then break the localization and lead to an enhancement in the transmission. For strong disorder, Anderson localization [ Phys. Rev. 109, 1492 (1958) ] sets in, causing the transmission to decrease. The phenomenon is robust and can occur with or without magnetic field.
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73.63.Bd Nanocrystalline materials
73.40.-c Electronic transport in interface structures
73.22.Pr Electronic structure of graphene
73.20.Fz Weak or Anderson localization
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Boron diffusion in magnetic tunnel junctions with MgO (001) barriers and CoFeB electrodes

H. Kurt, K. Rode, K. Oguz, M. Boese, C. C. Faulkner, and J. M. D. Coey

Appl. Phys. Lett. 96, 262501 (2010); http://dx.doi.org/10.1063/1.3457475 (3 pages) | Cited 7 times

Online Publication Date: 28 June 2010

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Boron diffusion out of the CoFeB layers in model systems with thick CoFeB and MgO layers grown by radiofrequency sputtering or electron-beam evaporation and in MgO-based magnetic tunnel junctions (MTJs) is probed after annealing by x-ray photoemission spectroscopy (XPS) and electron energy loss spectroscopy. Successive interfaces are exposed by ion milling the stacks, layer by layer, in the XPS system. Despite the presence of thick CoFeB and a high annealing temperature of 400 °C, we found no boron in the MgO or at the MgO/CoFe interfaces. Similar results are also obtained in the MTJs.
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81.15.Cd Deposition by sputtering
81.15.Dj E-beam and hot filament evaporation deposition
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.De Giant magnetoresistance
81.40.Gh Other heat and thermomechanical treatments
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Tuning of magnetism in ferromagnetic thin films by reversing the functional groups of molecular underlayer

Jung-Chi Tai, Jang-Chang Huang, Yin-Ming Chang, Kai-Shin Li, Jhen-Yong Hong, Sheng-Syun Wong, Wen-Chung Chiang, and Minn-Tsong Lin

Appl. Phys. Lett. 96, 262502 (2010); http://dx.doi.org/10.1063/1.3457907 (3 pages) | Cited 3 times

Online Publication Date: 28 June 2010

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We demonstrate a molecular approach of tuning the magnetic properties of ferromagnetic (FM) thin films by reversing the functional groups of the organic underlayer. For the CoFe/Langmuir–Blodgett (LB) film system, we find that the coercivity of CoFe thin films (from 4 to 10 nm) made on hydrophobic surfaces is significantly enhanced whereas that on hydrophilic surfaces remains unchanged, as compared with the films directly on glass substrates. These findings suggest an alternative way for tuning the magnetic properties of the FM layer by LB film in which the functional groups play an important role.
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75.70.-i Magnetic properties of thin films, surfaces, and interfaces
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces

Interfacial barrier in manganite junctions with different crystallographic orientations

W. W. Gao, A. D. Wei, J. R. Sun, D. S. Shang, J. Wang, T. Y. Zhao, and B. G. Shen

Appl. Phys. Lett. 96, 262503 (2010); http://dx.doi.org/10.1063/1.3447797 (3 pages) | Cited 2 times

Online Publication Date: 28 June 2010

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We performed a comprehensive study on the La1−xCaxMnO3/SrTiO3:Nb junctions with different hole content and film thickness. It is found that the interfacial barrier, which determines the physical properties of the junctions, shows a strong dependence on crystallographic orientation, and it is substantially higher for the (110) than for the (100)-orientated junctions. The difference in barrier height is further found to exhibit a systematic variation with Ca content and film thickness (t). It reduces from ∼ 0.09 to 0.02 eV for a x increase from 0.1 to 1 with a fixed t = 200 nm, and experiences a growth by ∼ 0.06 eV corresponding to the variation in t from 10 to 160 nm for a constant x = 0.33. Similar phenomena have been observed in the La0.67Ba0.33MnO3/SrTiO3:Nb junctions. In the scenario of different polarity mismatches at the (100) and (110) interfaces in the two series of junctions, these results can be qualitatively understood.
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73.20.-r Electron states at surfaces and interfaces
68.35.Ct Interface structure and roughness
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Reduced room-temperature ferromagnetism in intermediate conducting regime of V doped ZnO

S. H. Liu, H. S. Hsu, G. Venkataiah, X. Qi, C. R. Lin, J. F. Lee, K. S. Liang, and J. C. A. Huang

Appl. Phys. Lett. 96, 262504 (2010); http://dx.doi.org/10.1063/1.3456381 (3 pages) | Cited 9 times

Online Publication Date: 28 June 2010

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The mechanism of room temperature (RT) ferromagnetism for low doping concentration of 2.5% V in ZnO have been systematically discussed by measuring structural, electrical, and magnetic properties. The evolution of the Curie temperature from above RT in insulated V:ZnO powders to 270 K in semiconducting samples was observed with increasing carrier concentration by using different hydrogenated annealing treatment. The results provide a direct observation that the free carriers suppress the ferromagnetism and might be associated the phenomena of charge-transfer and interaction between bound magnetic polarons.
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81.05.Dz II-VI semiconductors
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
72.80.Ey III-V and II-VI semiconductors
61.72.uj III-V and II-VI semiconductors

Influence of edges on the exchange bias properties of ferromagnetic/antiferromagnetic nanodots

V. Baltz, G. Gaudin, P. Somani, and B. Dieny

Appl. Phys. Lett. 96, 262505 (2010); http://dx.doi.org/10.1063/1.3449123 (3 pages) | Cited 5 times

Online Publication Date: 28 June 2010

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For ferromagnetic (F)/antiferromagnetic (AF) nanodots contributions of AF spins to exchange bias is discussed. The relative weights of AF entities located at the dot edges, at the F/AF interface and in the AF grains were obtained by comparing the blocking temperature distribution of an array of nanodots with that of corresponding continuous film. Due to grain cutting, the grain size distribution is altered. We show here that the dot edges constitute additional locations for the formation of spin-glasslike AF regions at the F/AF interface. The result of patterning is thus twofold and weakens the dot ability to resist thermally activated magnetization reversal.
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75.60.Jk Magnetization reversal mechanisms
73.20.At Surface states, band structure, electron density of states
75.50.Ee Antiferromagnetics

Tunneling processes in thin MgO magnetic junctions

J. M. Teixeira, J. Ventura, J. P. Araujo, J. B. Sousa, P. Wisniowski, and P. P. Freitas

Appl. Phys. Lett. 96, 262506 (2010); http://dx.doi.org/10.1063/1.3458701 (3 pages) | Cited 3 times

Online Publication Date: 29 June 2010

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Magnetic tunnel junctions (MTJs) with MgO barriers are used in a variety of applications, from read heads to novel microwave devices. In this work, we probed the temperature (T) dependence of the electrical transport of sputtered CoFeB/MgO/CoFeB MTJs with different barrier thicknesses (tb = 0.75–1.35 nm). We show evidence that spin-polarized direct elastic tunneling is the dominant mechanism determining the T-dependence of the tunnel conductance (G) and magnetoresistance for tb ≥ 0.85 nm. Also, the electronic thermal smearing near the Fermi level plays a key role in G(T). We observe the onset of pinholes for MTJs with 0.75 nm of MgO, with a transition to metallic-like transport.
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75.47.Lx Magnetic oxides
72.25.-b Spin polarized transport
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Nature of short-range ferromagnetic ordered state above TC in double perovskite La2NiMnO6

S. M. Zhou, Y. Q. Guo, J. Y. Zhao, S. Y. Zhao, and L. Shi

Appl. Phys. Lett. 96, 262507 (2010); http://dx.doi.org/10.1063/1.3459141 (3 pages) | Cited 3 times

Online Publication Date: 30 June 2010

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Magnetic measurements of La2NiMnO6 reveal that its inverse susceptibility exhibits an upward derivation from Curie–Weiss behavior above TC, indicating the presence of a short-range ferromagnetic ordered state. It is suggested that the upward derivation is due to antiferromagnetic interactions arising from anitisite defects, which is supported by the magnetic studies on the samples where the antiferromagnetic interactions are modulated by partially doping La with Sr or by decreasing the sample size. Basing on these results, we propose that the short-range ferromagnetic ordering is induced by antisite defects against long-range ferromagnetic ordering of the Ni/Mn sublattice.
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75.50.Pp Magnetic semiconductors
75.30.Cr Saturation moments and magnetic susceptibilities
75.40.-s Critical-point effects, specific heats, short-range order

In situ tunneling measurements in a transmission electron microscope on nanomagnetic tunnel junctions

J. W. Lau, P. Morrow, J. C. Read, V. Höink, W. F. Egelhoff, L. Huang, and Y. Zhu

Appl. Phys. Lett. 96, 262508 (2010); http://dx.doi.org/10.1063/1.3446841 (3 pages) | Cited 2 times

Online Publication Date: 30 June 2010

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We showed that a chain of nanomagnetic tunnel junctions (MTJs) devices can be electrically addressed individually, in situ, in a transmission electron microscope, such that transport properties can be in principle, quantitatively correlated with each device’s defects and microstructure. A unique energy barrier was obtained for each device measured. Additionally, in situ tunneling magnetoresistance (TMR) measurements were obtained for a subset of devices. We found that TMR values for our nano-MTJs were generally smaller than TMR in the unpatterned film.
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85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields

Effect of structural relaxation and oxidation conditions on interlayer exchange coupling in Fe|MgO|Fe tunnel junctions

H. X. Yang, M. Chshiev, A. Kalitsov, A. Schuhl, and W. H. Butler

Appl. Phys. Lett. 96, 262509 (2010); http://dx.doi.org/10.1063/1.3459148 (3 pages) | Cited 2 times

Online Publication Date: 1 July 2010

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The effect of structural relaxation and interfacial oxidation is demonstrated from first principles to have a crucial impact on interlayer exchange coupling (IEC) in crystalline Fe|MgO|Fe magnetic tunnel junctions (MTJs). It is shown that the IEC becomes antiferromagnetic for the relaxed structure in contrast to ferromagnetic for unrelaxed Fe|MgO|Fe MTJs. Furthermore, the antiferromagnetic IEC is strongly enhanced in the presence of oxygen vacancies while it is decreased by overoxidation and may even become ferromagnetic for sufficiently high oxygen concentration at the Fe∣MgO interface. These results were supported using a tight-binding model and provide an explanation for recent experimental studies.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Ee Antiferromagnetics
81.65.Mq Oxidation

Asymmetric magnetic NOT gate and shift registers for high density data storage

Huang T. Zeng, D. Read, L. O’Brien, J. Sampaio, E. R. Lewis, D. Petit, and R. P. Cowburn

Appl. Phys. Lett. 96, 262510 (2010); http://dx.doi.org/10.1063/1.3457998 (3 pages) | Cited 5 times

Online Publication Date: 1 July 2010

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We have developed an asymmetric ferromagnetic NOT gate and shift register optimized on a square grid. This gives rise to a two-dimensional storage scheme built up by tessellating an elementary data unit, which is scalable down to very narrow wire widths. The areal footprint of each storage unit is 15F2, where F is the minimum feature size. We experimentally demonstrate NOT operations across a chain of three gates made from Permalloy with F = 60 nm, and present a functional 15-gate, multichannel shift register with electrical injection, and optical readout.
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84.30.Sk Pulse and digital circuits

Direct-write, focused ion beam-deposited, 7 K superconducting C–Ga–O nanowire

Pashupati Dhakal, G. McMahon, S. Shepard, T. Kirkpatrick, J. I. Oh, and M. J. Naughton

Appl. Phys. Lett. 96, 262511 (2010); http://dx.doi.org/10.1063/1.3458863 (3 pages) | Cited 1 time

Online Publication Date: 2 July 2010

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We have fabricated C–Ga–O nanowires by gallium focused ion beam-induced deposition from the carbon-based precursor phenanthrene. The electrical conductivity of the nanowires is weakly temperature dependent below 300 K and indicates a transition to a superconducting state below Tc = 7 K. We have measured the temperature dependence of the upper critical field Hc2(T) and estimate a zero temperature critical field of 8.8 T. The Tc of this material is approximately 40% higher than that of any other direct write nanowire, such as those based on C–W–Ga, expanding the possibility of fabricating direct-write nanostructures that superconduct above liquid helium temperatures.
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74.10.+v Occurrence, potential candidates
74.25.Op Mixed states, critical fields, and surface sheaths
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
74.62.-c Transition temperature variations, phase diagrams
74.70.-b Superconducting materials other than cuprates

High magnetomechanical coupling on magnetic microwire for sensors with biological applications

P. Marín, M. Marcos, and A. Hernando

Appl. Phys. Lett. 96, 262512 (2010); http://dx.doi.org/10.1063/1.3459140 (3 pages) | Cited 3 times

Online Publication Date: 2 July 2010

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In this letter, we report the experimental work carried out to study and improve the magnetomechanical coupling on magnetic microwires. A good magnetoelastic response, with magnetoelastic coupling factor k = 0.43, has been obtained by control of both wire diameter and sample microstructure. The study addresses two following aspects: (a) analysis of the suitability of amorphous magnetoelastic microwire as promising tiny sensor element to be used as wireless biosensors as well as environment detectors. In particular, its potential as liquids viscosity sensor has been confirmed. (b) Study, as the first time in this kind of magnetic microwire, of the effects of nanocrystallization on the sample magnetoelastic behavior.
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07.10.Cm Micromechanical devices and systems
83.85.Jn Viscosity measurements
87.64.-t Spectroscopic and microscopic techniques in biophysics and medical physics
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
75.80.+q Magnetomechanical effects, magnetostriction
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
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Transition of stable rectification to resistive-switching in Ti/TiO2/Pt oxide diode

Jiun-Jia Huang, Chih-Wei Kuo, Wei-Chen Chang, and Tuo-Hung Hou

Appl. Phys. Lett. 96, 262901 (2010); http://dx.doi.org/10.1063/1.3457866 (3 pages) | Cited 23 times

Online Publication Date: 28 June 2010

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We have fabricated a Ti/TiO2/Pt oxide diode with excellent rectifying characteristics by the asymmetric Schottky barriers at the Ti/TiO2 (0.13 eV) and the TiO2/Pt (0.73 eV) interfaces. Instead of homogeneous conduction, the current transport is governed by the localized oxygen-deficient TiO2 filaments. In addition, the reproducible resistive-switching exists in the same structure, triggered by the forming process. The transition between two modes is ascribed to the destruction of the interface barriers at forming. The rectification stable up to 125 °C and 103 cycles under ±3 V sweep without interference with resistive-switching shows satisfactory reliability of TiO2 diodes for one diode-one resistor memory devices.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Rw Metal-insulator-metal structures
73.40.Ei Rectification

Effect of electrode configurations on the process-induced imprint behavior of epitaxial Pb(Zr0.52Ti0.48)O3 capacitors

Feng Chen, Xuelian Tan, Zhen Huang, Xiaofeng Xuan, and Wenbin Wu

Appl. Phys. Lett. 96, 262902 (2010); http://dx.doi.org/10.1063/1.3458599 (3 pages) | Cited 6 times

Online Publication Date: 28 June 2010

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By using La0.7Sr0.3MnO3 (L) and SrRuO3 (S) electrodes, epitaxial Pb(Zr0.52Ti0.48)O3 (PZT) capacitors with different electrode configurations, i.e., L/PZT/L (from top to bottom) (a), S/PZT/S (b), S/PZT/L (c), and L/PZT/S (d), have been fabricated and the process-induced imprint was investigated. All as-grown capacitors are nearly imprint-free; however, after being annealed at 10−5 Torr of O2 the capacitors a (b) show a large negative (positive) imprinted polarization (P) state at zero electric-field (E), the capacitors c give strongly pinched P-E hysteresis loops, and the capacitors d are highly resistant to imprint failure. We show evidence that the internal fields could be attributed to the various oxygen-loss-related strain gradients at PZT top and bottom interfaces, induced during the annealing.
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84.32.Tt Capacitors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.80.Dj Domain structure; hysteresis
61.72.Cc Kinetics of defect formation and annealing
77.22.Ej Polarization and depolarization

Temperature-dependent Raman scattering of KTa1−xNbxO3 thin films

A. Bartasyte, J. Kreisel, W. Peng, and M. Guilloux-Viry

Appl. Phys. Lett. 96, 262903 (2010); http://dx.doi.org/10.1063/1.3455326 (3 pages) | Cited 3 times

Online Publication Date: 30 June 2010

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We report a Raman scattering investigation of KTa1−xNbxO3 (x = 0.35,0.5) thin films deposited on MgO and LaAlO3 as a function of temperature. The observed phase sequence in the range from 90 to 720 K is similar to the structural phase transitions of the end-member material KNbO3. Although similar in the phase sequence, the actual temperatures observed for phase transition temperatures are significantly different from those observed in the literature for bulk samples. Namely, the tetragonal (ferroelectric) to cubic (paraelectric) phase transition is up to 50 K higher in the films when compared to bulk samples. This enhanced ferroelectricity is attributed to biaxial strain in the investigated thin films.
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77.55.F- High-permittivity capacitive films
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
78.30.-j Infrared and Raman spectra
77.80.-e Ferroelectricity and antiferroelectricity

Effects of electrical stress on the leakage current characteristics of multilayer capacitor structures

Soon-Wook Kim, Sung Kyun Lee, Young Do Kim, and Sibum Kim

Appl. Phys. Lett. 96, 262904 (2010); http://dx.doi.org/10.1063/1.3456731 (3 pages) | Cited 4 times

Online Publication Date: 1 July 2010

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Show Abstract
The degradation of a high-k dielectric multilayer was investigated by measuring the time dependent leakage current under a constant voltage stress in metal-insulator-metal capacitor structures. When comparing the two multilayer structures of Al2O3/HfO2/Al2O3 and HfO2/Al2O3/HfO2, the former was characterized by a large fluctuation of the leakage current and the latter had an increased leakage current at the initial stage. These results are related to the different voltage drops of each individual layer as well as the thickness impact on the behavior of the current density versus electric field.
Show PACS
84.32.Tt Capacitors
77.22.Jp Dielectric breakdown and space-charge effects
77.55.F- High-permittivity capacitive films
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