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19 Apr 2010

Volume 96, Issue 16, Articles (16xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 96, 163101 (2010); http://dx.doi.org/10.1063/1.3327831 (3 pages)

Ramesh Nath, Seungbum Hong, Jeffrey A. Klug, Alexandra Imre, Michael J. Bedzyk, Ram S. Katiyar, and Orlando Auciello
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Depth-dependence of electrical conductivity of diamondlike carbon films

A. Sikora, P. Paolino, H. Ftouni, C. Guerret-Piécourt, J.-L. Garden, A.-S. Loir, F. Garrelie, C. Donnet, and O. Bourgeois

Appl. Phys. Lett. 96, 162111 (2010); http://dx.doi.org/10.1063/1.3407671 (3 pages) | Cited 1 time

Online Publication Date: 23 April 2010

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The electrical behavior of diamondlike carbon (DLC) has been measured as a function of depth. The amorphous carbon (a-C) films are deposited by pulsed laser deposition using two complementary setups: a femtosecond (fs) and a nanosecond (ns) pulse lasers. It is demonstrated through four probe resistance measurements and contact resistance mapping that the fs DLC are electrically heterogeneous in thickness. The presence of a thick sp2 rich layer on top is evidenced for fs a-C and is apparently away in the sp3 rich ns a-C. It is attributed to different subplantation processes between ns and fs a-C films.
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73.61.Wp Fullerenes and related materials
81.15.Fg Pulsed laser ablation deposition
73.40.Cg Contact resistance, contact potential

Scattering mechanism in modulation-doped shallow two-dimensional electron gases

D. Laroche, S. Das Sarma, G. Gervais, M. P. Lilly, and J. L. Reno

Appl. Phys. Lett. 96, 162112 (2010); http://dx.doi.org/10.1063/1.3402765 (3 pages) | Cited 4 times

Online Publication Date: 23 April 2010

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We report on a systematic investigation of the dominant scattering mechanism in shallow two-dimensional electron gases (2DEGs) formed in modulation-doped GaAs/AlxGa1−xAs heterostructures. The power-law exponent of the electron mobility versus density, μ∝nα, is extracted as a function of the 2DEG’s depth. When shallower than 130 nm from the surface, the power-law exponent of the 2DEG, as well as the mobility, drops from α ≃ 1.65 (130 nm deep) to α ≃ 1.3 (60 nm deep). Our results for shallow 2DEGs are consistent with theoretical expectations for scattering by remote dopants, in contrast to the mobility-limiting background charged impurities of deeper heterostructures.
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73.20.At Surface states, band structure, electron density of states
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Interactions between 180° and 360° domain walls in magnetic multilayer stripes

Mark D. Mascaro, Chunghee Nam, and C. A. Ross

Appl. Phys. Lett. 96, 162501 (2010); http://dx.doi.org/10.1063/1.3396076 (3 pages) | Cited 8 times

Online Publication Date: 20 April 2010

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Magnetostatic interactions between 360° and transverse 180° domain walls in the NiFe and Co layers of Co/Cu/NiFe multilayer stripes are investigated by micromagnetic simulations. In 200 nm wide Co (5 nm)/Cu (5 nm) /NiFe (5 nm) stripes, stray fields from 360° domain walls in the Co layer strongly influence the magnetic behavior of the NiFe layer, promoting reverse domain nucleation and providing a pinning potential of order 100 Oe which impedes domain wall propagation. 360° domain walls may be useful as programmable pinning sites in magnetoelectronic logic or memory devices.
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75.60.Ch Domain walls and domain structure
75.78.Cd Micromagnetic simulations
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.65.Ac Multilayers
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Exchange bias in spin glass (FeAu)/NiFe thin films

Fu-Te Yuan, Jeng-Kai Lin, Y. D. Yao, and Shang-Fan Lee

Appl. Phys. Lett. 96, 162502 (2010); http://dx.doi.org/10.1063/1.3399780 (3 pages) | Cited 7 times

Online Publication Date: 20 April 2010

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The exchange bias of a ferromagnet in contact with a spin glass is evidenced in the sputter deposited (Fe 9.6 at. % Au)/NiFe bilayers. The biasing field decreases as temperature increases, change the sign after reaching a compensation temperature (To), and are reduced to zero at higher temperatures. Furthermore, To decreases with the decreasing FeAu layer thickness. Likewise, the inverse bias decreases with the increasing maximum field of a hysteresis loop. A spin structure model is suggested to explain our data. The results confirm the robust nature of the inverse bias in spin glass/ferromagnetic structure and reveal distinct physics from conventional antiferromagnetic/ferromagnetic systems.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Lk Spin glasses and other random magnets
75.50.Bb Fe and its alloys

Magnetization plateau and incommensurate spin modulation in Ca3Co2O6

Yang Zhao, Shou-Shu Gong, Wei Li, and Gang Su

Appl. Phys. Lett. 96, 162503 (2010); http://dx.doi.org/10.1063/1.3413931 (3 pages) | Cited 3 times

Online Publication Date: 21 April 2010

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The magnetic properties of a trigonal prism unit of the spin-2 frustrated compound Ca3Co2O6 are studied by means of the density-matrix renormalization group method. A magnetization plateau at ms/3 (ms is the saturation magnetization) with ferrimagnetic structure is observed. By fitting the experimental data of magnetic curve, an estimation of the couplings gives J1 = −26.84 K, J2 = 0.39 K, and J3 = 0.52 K. The local magnetic moments are unveiled to exhibit an incommensurate sinusoidally modulation along the three chains of the trigonal prism, which gives a strong theoretical support to the experimentally observed incommensurate partially disordered antiferromagnetic state for Ca3Co2O6. The present result suggests that the modulation indeed originates from the competition of antiferromagnetic and ferromagnetic couplings.
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75.10.Jm Quantized spin models, including quantum spin frustration
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Et Exchange and superexchange interactions
75.50.Ee Antiferromagnetics
75.20.Hr Local moment in compounds and alloys; Kondo effect, valence fluctuations, heavy fermions
75.50.Gg Ferrimagnetics

(Fe,Si,Al)-based nanocrystalline soft magnetic alloys for cryogenic applications

Maria Daniil, Michael S. Osofsky, Donald U. Gubser, and Matthew A. Willard

Appl. Phys. Lett. 96, 162504 (2010); http://dx.doi.org/10.1063/1.3402775 (3 pages) | Cited 5 times

Online Publication Date: 21 April 2010

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In this work Al and Si are substituted for Fe in a (Fe,Si,Al)–Nb–B–Cu alloy with the goal of improving its magnetic properties at 77 K. The x-ray diffraction patterns for a series of five alloys annealed at 823 K shows a Fe3(Si,Al) ordered phase with some residual amorphous phase. The lowest coercivity at room temperature was observed for the alloy with composition Fe68Si15.5Al3.5Nb3B9Cu1. At cryogenic temperatures, the saturation magnetization of 99.3 A m2/kg, coercivity of 0.45 A/m, and resistivity of 122 μΩ cm for the Fe63Si17.5Al6Nb3B9Cu1 alloy, compare favorably to commercial alloys at 77 K.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.40.Gh Other heat and thermomechanical treatments
75.50.-y Studies of specific magnetic materials

A magnetoelectric memory cell with coercivity state as writing data bit

Zheng Li, Jing Wang, Yuanhua Lin, and C. W. Nan

Appl. Phys. Lett. 96, 162505 (2010); http://dx.doi.org/10.1063/1.3405722 (3 pages) | Cited 7 times

Online Publication Date: 21 April 2010

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Commercial magnetic recording media employ magnetic-field-induced two different magnetization states ±M to write data. In this paper, we present a magnetic memory cell in which electric-field-induced two different coercive-field Hc states (i.e., low-Hc and high-Hc) rather than ±M are served as writing data bits. A multiferroic magnetoelectric bilayer with Fe0.93Ge0.07 film grown on fully poled ferroelectric BiScO3-PbTiO3 substrate, exhibiting a large electric-field modulation of Hc, is used for illustration of such a prototype electric-write/magnetic-read memory cell which is nonvolatile. The reading process of the different coercive-field Hc information written by electric fields is demonstrated by using magnetoresistance read head.
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85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
85.75.Bb Magnetic memory using giant magnetoresistance
77.55.Nv Multiferroic/magnetoelectric films
75.85.+t Magnetoelectric effects, multiferroics
77.80.-e Ferroelectricity and antiferroelectricity

Optimal time-dependent current pattern for domain wall dynamics in nanowires

P. Yan and X. R. Wang

Appl. Phys. Lett. 96, 162506 (2010); http://dx.doi.org/10.1063/1.3413951 (3 pages) | Cited 2 times

Online Publication Date: 22 April 2010

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Optimal current pattern for domain wall (DW) dynamics in nanowires is investigated. Based on the modified Landau–Lifshitz–Gilbert equation with both the Slonczewski spin-transfer torque and the fieldlike torque, the optimal current pattern for either the maximal DW propagation velocity or the maximal DW-motion-induced spin electromotive voltage is found. Possible experimental realizations are discussed.
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75.60.Ch Domain walls and domain structure
75.75.Fk Domain structures in nanoparticles
75.50.Tt Fine-particle systems; nanocrystalline materials
75.75.-c Magnetic properties of nanostructures
75.30.Ds Spin waves
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From single- to double-first-order magnetic phase transition in magnetocaloric Mn1−xCrxCoGe compounds

N. T. Trung, V. Biharie, L. Zhang, L. Caron, K. H. J. Buschow, and E. Brück

Appl. Phys. Lett. 96, 162507 (2010); http://dx.doi.org/10.1063/1.3399774 (3 pages) | Cited 18 times

Online Publication Date: 22 April 2010

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Substitution of some Cr for Mn atoms in MnCoGe was employed to control the magnetic and structural transitions in this alloy to coincide, leading to a single first-order magnetostructural transition from the ferromagnetic to the paramagnetic state with a giant magnetocaloric effect observed near room temperature. Further increase in the Cr content in the Mn1−xCrxCoGe alloys can induce another first-order magnetoelastic transition from the antiferromagnetic to the ferromagnetic state occurring at lower temperature. The giant magnetocaloric effect as well as the simultaneous tunability of the two magnetic transitions make these materials promising for future cooling applications.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.30.Sg Magnetocaloric effect, magnetic cooling
75.80.+q Magnetomechanical effects, magnetostriction
75.50.Dd Nonmetallic ferromagnetic materials

Origin of antiferromagnetism in CoO: A density functional theory study

Hui-Xiong Deng, Jingbo Li, Shu-Shen Li, Jian-Bai Xia, Aron Walsh, and Su-Huai Wei

Appl. Phys. Lett. 96, 162508 (2010); http://dx.doi.org/10.1063/1.3402772 (3 pages) | Cited 1 time

Online Publication Date: 22 April 2010

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We have investigated the origin of antiferromagnetism of CoO in the rocksalt structure using spin-polarized density functional theory calculations. We find that in the rocksalt structure, the superexchange interaction between the occupied and unoccupied eg states plays the dominant role, which leads to an antiferromagnetic ground state, but the system also has a strong direct exchange interaction between the partially occupied minority spin t2g states that leads to the unusual situation that the ferromagnetic phase is more stable than most antiferromagnetic configurations.
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75.30.Et Exchange and superexchange interactions
75.50.Dd Nonmetallic ferromagnetic materials
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
75.50.Ee Antiferromagnetics
72.25.-b Spin polarized transport
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
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Effect of postdeposition annealing on the structural and electrical characteristics of Yb2TiO5 charge trapping layers

Tung-Ming Pan, Ji-Shing Jung, and Xin-Chang Wu

Appl. Phys. Lett. 96, 162901 (2010); http://dx.doi.org/10.1063/1.3402774 (3 pages) | Cited 3 times

Online Publication Date: 20 April 2010

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In this letter, we proposed a metal-oxide-high-k-oxide-silicon-type (MOHOS) memory structure incorporating a high-k Yb2TiO5 charge trapping layer and the subsequent postdeposition annealing treatment. The effect of postdeposition annealing on the structural properties of Yb2TiO5 charge trapping layers was explored by x-ray diffraction, transmission electron microscopy, and x-ray photoelectron spectroscopy. The Yb2TiO5 MOHOS-type device annealed at 800 °C exhibited a larger memory window of 2.8 V and a smaller charge loss of 10% than did those prepared at other annealing temperatures. This outcome is attributed to the higher probability for trapping the charge carrier due to the formation of a well-crystallized Yb2TiO5 structure and a thin low-k interfacial layer.
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84.30.Sk Pulse and digital circuits
61.72.Cc Kinetics of defect formation and annealing
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
79.60.-i Photoemission and photoelectron spectra

Photoinduced charge-trapping phenomena in metal/high-k gate stack structures studied by synchrotron radiation photoemission spectroscopy

T. Tanimura, S. Toyoda, H. Kamada, H. Kumigashira, M. Oshima, T. Sukegawa, G. L. Liu, and Z. Liu

Appl. Phys. Lett. 96, 162902 (2010); http://dx.doi.org/10.1063/1.3409162 (3 pages) | Cited 3 times

Online Publication Date: 21 April 2010

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We have demonstrated photoinduced charge-trapping phenomena in metal/high-k gate stack structures using time-dependent photoemission spectroscopy with synchrotron radiation. Pt metal gate electrode with a large work function releases trapped negative charges near the surface of the HfSiON film while TiN metal gate electrode with a lower work function keeps negative charges in the HfSiON film. The release of negative trapped charges reveals a possibility of positive charge trapping at the interface in the HfSiON film. The location of energy level for negative charges is concluded to be between Pt and TiN Fermi-level in the band gap of the HfSiON film.
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77.55.D- High-permittivity gate dielectric films
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.-r Electrical properties of specific thin films
73.20.At Surface states, band structure, electron density of states
73.30.+y Surface double layers, Schottky barriers, and work functions
79.60.-i Photoemission and photoelectron spectra

Unusual dielectric response in B-site size-disordered hexagonal transition metal oxides

Debraj Choudhury, Adyam Venimadhav, Chandrasekhar Kakarla, Kris T. Delaney, P. Sujatha Devi, P. Mondal, R. Nirmala, J. Gopalakrishnan, Nicola A. Spaldin, Umesh V. Waghmare, and D. D. Sarma

Appl. Phys. Lett. 96, 162903 (2010); http://dx.doi.org/10.1063/1.3379293 (3 pages) | Cited 1 time

Online Publication Date: 21 April 2010

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We discover that hexagonal holmium copper titanate (Ho2CuTiO6), has a unique and highly desirable combination of high dielectric constant, low losses, very small temperature coefficient, and low frequency dependence. Our first-principles calculations indicate that these exceptional properties result from a size-difference at the Cu/Ti B-site that suppresses the expected ferroelectric transition, combined with the dominance of intermediate-frequency polar vibrational modes in the dielectric response. Our results suggest that the use of such B-site disorder in alloys of hexagonal transition-metal oxides should generally result in similar robust dielectrics.
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77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
77.84.Cg PZT ceramics and other titanates
63.20.-e Phonons in crystal lattices
77.80.B- Phase transitions and Curie point

Particle size reduction: A way to enhanced dielectric properties of magnetocapacitive La2/3Ca1/3MnO3

S. Yáñez-Vilar, J. Mira, M. Sánchez-Andújar, S. Castro-García, A. Fondado, J. Rivas, and M. A. Señarís-Rodríguez

Appl. Phys. Lett. 96, 162904 (2010); http://dx.doi.org/10.1063/1.3394004 (3 pages) | Cited 2 times

Online Publication Date: 21 April 2010

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We report the optimization of the dielectric properties of La2/3Ca1/3MnO3. This is achieved by synthesizing this material with small particle size, strategy that reduces the conductivity of the sample and its dielectric losses, while retaining a reasonably high dielectric permittivity and a good magnetocapacitive response. In order to further improve the properties of these nanoparticles, we have also prepared core-shell composites La2/3Ca1/3MnO3@SiO2 but in this case the magnetocapacitive effect is strongly reduced.
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77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.84.Lf Composite materials

Effect of intrinsic surface stress on single-vertex structure of polarization in ferroelectric nanoparticles

Yu Su and Jing-Na Du

Appl. Phys. Lett. 96, 162905 (2010); http://dx.doi.org/10.1063/1.3409122 (3 pages) | Cited 4 times

Online Publication Date: 23 April 2010

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Intrinsic surface stress forms due to the relatively high surface energy of nanoscale ferroelectrics. Such surface stress induces mechanical balancing stress below the curved free surfaces, and consequently affects the existence of singe-vertex structure of polarization within free-standing ferroelectric nanostructures. A thermodynamics-based continuum phase field approach is employed to investigate such surface effect in ferroelectric nanodisks. It has been observed that, for a given material, the minimum geometric limit for existence of single-vertex structure will generally be elevated upon the compressive surface-induced stress. Such increase is nonlinear, and highly depending on the energy exchange parameter in the model.
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77.22.Ej Polarization and depolarization
68.35.Md Surface thermodynamics, surface energies
62.25.-g Mechanical properties of nanoscale systems
05.70.Np Interface and surface thermodynamics

Effects of capping HfO2 with multivalent oxides toward reducing the number of charged defects

Naoto Umezawa

Appl. Phys. Lett. 96, 162906 (2010); http://dx.doi.org/10.1063/1.3409222 (3 pages) | Cited 3 times

Online Publication Date: 23 April 2010

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Electrical properties of field-effect transistors are significantly degraded by charged defects formed in dielectric oxides. Here, we propose a simple method for eliminating charged defects in HfO2. Our computational and thermodynamic investigations have revealed that multivalent oxides act as an oxygen reservoir when deposited on HfO2, playing an important role in keeping the oxygen chemical potential constant throughout the oxide film. This is due to the coexistence of two stoichiometric phases in the multivalent oxide, which allows absorption or desorption of oxygen atoms depending on the ambient conditions. Our theory predicts europium oxide is the best capping material for minimizing oxygen-related charged defects in HfO2.
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77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials

Giant dielectric constant dominated by Maxwell–Wagner relaxation in Al2O3/TiO2 nanolaminates synthesized by atomic layer deposition

Wei Li, Orlando Auciello, Ramesh N. Premnath, and Bernd Kabius

Appl. Phys. Lett. 96, 162907 (2010); http://dx.doi.org/10.1063/1.3413961 (3 pages) | Cited 10 times

Online Publication Date: 23 April 2010

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Nanolaminates consisting of Al2O3 and TiO2 oxide sublayers were synthesized by using atomic layer deposition to produce individual layers with atomic scale thickness control. The sublayer thicknesses were kept constant for each multilayer structure, and were changed from 50 to 0.2 nm for a series of different samples. Giant dielectric constant ( ∼ 1000) was observed when the sublayer thickness is less than 0.5 nm, which is significantly larger than that of Al2O3 and TiO2 dielectrics. Detailed investigation revealed that the observed giant dielectric constant is originated from the Maxwell–Wagner type dielectric relaxation.
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77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
77.55.-g Dielectric thin films
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.65.Ac Multilayers
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Effects of cantilever buckling on vector piezoresponse force microscopy imaging of ferroelectric domains in BiFeO3 nanostructures

Ramesh Nath, Seungbum Hong, Jeffrey A. Klug, Alexandra Imre, Michael J. Bedzyk, Ram S. Katiyar, and Orlando Auciello

Appl. Phys. Lett. 96, 163101 (2010); http://dx.doi.org/10.1063/1.3327831 (3 pages) | Cited 14 times

Online Publication Date: 19 April 2010

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Systematic studies are presented on the effects of cantilever buckling in vector piezoresponse force microscopy (V-PFM) imaging of polarization domains in thin-film based (001)-oriented BiFeO3 nanostructures, as observed through the coupling of out-of-plane and in-plane PFM images. This effect is a strong function of the laser spot position on the cantilever, being strongest at the free end, and insignificant at 60% of the cantilever length from the pivot point. This finding provides a unique approach to V-PFM imaging of ferroelectric polarization domains, yielding three dimensional PFM images without sample rotation in the plane.
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77.80.Dj Domain structure; hysteresis
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
77.80.-e Ferroelectricity and antiferroelectricity
77.55.F- High-permittivity capacitive films
62.20.mq Buckling
81.40.Lm Deformation, plasticity, and creep

Electronic and magnetic properties of zigzag graphene nanoribbon with one edge saturated

B. Xu, J. Yin, Y. D. Xia, X. G. Wan, K. Jiang, and Z. G. Liu

Appl. Phys. Lett. 96, 163102 (2010); http://dx.doi.org/10.1063/1.3402762 (3 pages) | Cited 17 times

Online Publication Date: 19 April 2010

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We investigated the energetic stability, electronic, and magnetic properties of the zigzag graphene nanoribbons with one edge saturated by two hydrogen atoms, the other edge saturated by one hydrogen atom by using density-functional theory (DFT). The energy of the ferromagnetic semiconductor state is the lowest state for these nanoribbons. The energy difference between the antiferromagnetic states and the ferromagnetic states varies inversely with the nanoribbon width. Both the band gaps and the magnetic moments in the zigzag graphene nanoribbons with one edge saturated are larger than those of zigzag graphene nanoribbons.
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73.22.Pr Electronic structure of graphene
78.67.Wj Optical properties of graphene
75.75.-c Magnetic properties of nanostructures
75.50.Pp Magnetic semiconductors
75.30.Cr Saturation moments and magnetic susceptibilities
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

One-dimensional alignment of nanoparticles via magnetic sorting

R. Bouskila, R. McAloney, S. Mack, D. D. Awschalom, M. C. Goh, and K. S. Burch

Appl. Phys. Lett. 96, 163103 (2010); http://dx.doi.org/10.1063/1.3405732 (3 pages) | Cited 1 time

Online Publication Date: 19 April 2010

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Near room temperature, MnAs films align into two phases, one ferromagnetic and the other paramagnetic. These phases take the intriguing form of nanoscale wires. We have exploited this phase coexistence to form linear arrays of magnetite nanoparticles without the need for photolithography. This is confirmed via extensive scanning probe microscopy.
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81.07.Bc Nanocrystalline materials
75.50.Dd Nonmetallic ferromagnetic materials
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Tt Fine-particle systems; nanocrystalline materials
75.75.-c Magnetic properties of nanostructures
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Photoinduced deformation of azopolymer nanometric spheres

R. Barillé, P. Tajalli, S. Kucharski, E. Ortyl, and J.-M. Nunzi

Appl. Phys. Lett. 96, 163104 (2010); http://dx.doi.org/10.1063/1.3409123 (3 pages) | Cited 3 times

Online Publication Date: 20 April 2010

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Nanometric spheres of an azopolymer are obtained by micellization from a solution. We observe photoinduced deformation of the individual nanospheres under white light illumination. The diameter expands up to 35% parallel to the substrate surface. The magnitude of the force that is necessary to produce the same effect is estimated.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Mechanical control of magnetic states of finite carbon chains encapsulated in single wall carbon nanotubes

B. Xu, J. Y. Lin, and Y. P. Feng

Appl. Phys. Lett. 96, 163105 (2010); http://dx.doi.org/10.1063/1.3397995 (3 pages) | Cited 1 time

Online Publication Date: 20 April 2010

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Effects of a lateral strain on finite carbon chains encapsulated in armchair carbon nanotubes are investigated using spin-polarized density functional theory. A strain induced transition between magnetic and nonmagnetic states of the encapsulated carbon chain is predicted at certain value of the applied strain which can be easily achieved experimentally, due to variation in interaction strength between the single wall carbon nanotube and the encapsulated carbon chain. Furthermore, this transition is reversible within a certain range of the applied strain. The proposed mechanical control of magnetic state of the hybrid system opens possibility for nanodevices such as mechanomagnetic switch or piezomagnetic sensors.
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75.80.+q Magnetomechanical effects, magnetostriction
75.75.-c Magnetic properties of nanostructures
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

GaN nanowire surface state observed using deep level optical spectroscopy

A. Armstrong, Q. Li, Y. Lin, A. A. Talin, and G. T. Wang

Appl. Phys. Lett. 96, 163106 (2010); http://dx.doi.org/10.1063/1.3404182 (3 pages) | Cited 13 times

Online Publication Date: 20 April 2010

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Deep level defects in n-type GaN nanowires (NWs) with and without an epitaxially-grown AlGaN shell were compared using photoconductivity-mode deep level optical spectroscopy. Hole photoemission from a defect state located approximately 2.6 eV above the valence band was observed for GaN NWs but was not observed for AlGaN/GaN core-shell NWs, indicating that this deep level is associated with a GaN surface state. Identifying GaN NW surface states and developing an effective passivation mechanism is expected to aid in the understanding and improvement of GaN NW-based sensors and optoelectronics.
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71.55.Eq III-V semiconductors
72.40.+w Photoconduction and photovoltaic effects
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Single charge detection of an electron created by a photon in a g-factor engineered quantum dot

Makoto Kuwahara, Takeshi Kutsuwa, Keiji Ono, and Hideo Kosaka

Appl. Phys. Lett. 96, 163107 (2010); http://dx.doi.org/10.1063/1.3407513 (3 pages) | Cited 3 times

Online Publication Date: 21 April 2010

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We demonstrate that a single photoelectron can be trapped in a single quantum dot, which is formed by gate-defining with a nearly-zero g-factor quantum well, and a charge state can be detected with a quantum point contact without destruction. The detection yield has a peak of 0.27 at the resonant photon energy of the dot exciton in photon flux of 4.1×10−10 W/mm2. The number-resolved counting statistics revealed that the yield for the second electron trap is drastically decreased from that for the first trap because of the Coulomb-blockade effect. The demonstrated function is essential for making a high-fidelity quantum interface.
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73.23.Hk Coulomb blockade; single-electron tunneling
72.40.+w Photoconduction and photovoltaic effects
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.63.Rt Nanoscale contacts
73.23.-b Electronic transport in mesoscopic systems

Enhanced generation of single optically active spins in diamond by ion implantation

Boris Naydenov, V. Richter, Johannes Beck, Matthias Steiner, Philipp Neumann, Gopalakrishnan Balasubramanian, Jocelyn Achard, Fedor Jelezko, Jörg Wrachtrup, and Rafi Kalish

Appl. Phys. Lett. 96, 163108 (2010); http://dx.doi.org/10.1063/1.3409221 (3 pages) | Cited 14 times

Online Publication Date: 22 April 2010

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Show Abstract
The nitrogen-vacancy (NV) centers in diamond are amongst the most promising candidates for quantum information applications. Up to now the creation of such defects was highly probabilistic, requiring many copies of the nanodevice. Here we show that by employing a two step implantation process which includes low dose N2+ molecular ion implantations followed by high dose C implantation can increase the generation efficiency of NV centers by over 50%. Moreover, we detected intrinsic 14N concentration as low as 0.07 ppb by converting the nitrogen impurities into NV and then counting the single centers by using a confocal microscope.
Show PACS
61.72.U- Doping and impurity implantation
61.72.jd Vacancies
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