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20 Oct 2008

Volume 93, Issue 16, Articles (16xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 93, 161101 (2008); http://dx.doi.org/10.1063/1.3000630 (3 pages)

E. Mujagić, L. K. Hoffmann, S. Schartner, M. Nobile, W. Schrenk, M. P. Semtsiv, M. Wienold, W. T. Masselink, and G. Strasser
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Spectral diffusion and line broadening in single self-assembled GaAs/AlGaAs quantum dot photoluminescence

M. Abbarchi, F. Troiani, C. Mastrandrea, G. Goldoni, T. Kuroda, T. Mano, K. Sakoda, N. Koguchi, S. Sanguinetti, A. Vinattieri, and M. Gurioli

Appl. Phys. Lett. 93, 162101 (2008); http://dx.doi.org/10.1063/1.3003578 (3 pages) | Cited 16 times

Online Publication Date: 20 October 2008

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We experimentally and theoretically investigate the photoluminescence broadening of different excitonic complexes in single self-assembled GaAs/AlGaAs quantum dots. We demonstrate that the excitonic fine-structure splitting leads to a sizable line broadening whenever the detection is not resolved in polarization. The residual broadening in polarized measurements is systematically larger for the exciton with respect to both the trion and the biexciton recombination. The experimental data agree with calculations of the quantum confined Stark effect induced by charge defects in the quantum dot (QD) environment, denoting the role of the QD spectator carrier rearrangement in reducing the perturbation of the fluctuating environment.
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68.65.Hb Quantum dots (patterned in quantum wells)
82.45.Vp Semiconductor materials in electrochemistry
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.55.Et II-VI semiconductors
78.20.Jq Electro-optical effects

Solar cells on low-resistivity boron-doped Czochralski-grown silicon with stabilized efficiencies of 20%

Bianca Lim, Sonja Hermann, Karsten Bothe, Jan Schmidt, and Rolf Brendel

Appl. Phys. Lett. 93, 162102 (2008); http://dx.doi.org/10.1063/1.3003871 (3 pages) | Cited 4 times

Online Publication Date: 20 October 2008

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Recently, it was shown that the boron-oxygen complex responsible for the light-induced lifetime degradation in oxygen-rich boron-doped silicon can be permanently deactivated by illumination at elevated temperatures. Since the degradation is particularly harmful in low-resistivity Czochralski silicon (Cz-Si), we apply the deactivation procedure to a high-efficiency rear interdigitated single evaporation emitter wrap-through solar cell made on 1.4 Ω cm B-doped Cz-Si. The energy conversion efficiency is thereby increased by more than 1% absolute compared to the degraded state to 20.3% on a designated area of 92 cm2 and is furthermore shown to be stable under illumination at room temperature.
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84.60.Jt Photoelectric conversion

Solvent effects and multiple aggregate states in high-mobility organic field-effect transistors based on poly(bithiophene-alt-thienothiophene)

Shuai Wang, Jie-Cong Tang, Li-Hong Zhao, Rui-Qi Png, Loke-Yuen Wong, Perq-Jon Chia, Hardy S. O. Chan, Peter K.-H. Ho, and Lay-Lay Chua

Appl. Phys. Lett. 93, 162103 (2008); http://dx.doi.org/10.1063/1.3001574 (3 pages) | Cited 7 times

Online Publication Date: 21 October 2008

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Franck–Condon absorption analysis reveals the existence of several aggregate states in poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT) thin films which impact their recrystallization and the attainable field-effect mobility (μFET). Poor solvents (toluene and mixed-xylenes) lock in both disordered and well-ordered states that cannot be annealed away even in the liquid crystalline phase. This reduces μFET and increases mobility activation energies compared with films from good solvents (chlorobenzene and o-dichlorobenzene). Despite its poor solubility characteristics, PBTTT can be ink-jet printed in dilute chlorobenzene, and devices can be operated unencapsulated in ambient, in the dark (>105 cycles over several days) with only a moderate mobility loss.
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85.30.Tv Field effect devices

Self-diffusion in germanium isotope multilayers at low temperatures

E. Hüger, U. Tietze, D. Lott, H. Bracht, D. Bougeard, E. E. Haller, and H. Schmidt

Appl. Phys. Lett. 93, 162104 (2008); http://dx.doi.org/10.1063/1.3002294 (3 pages) | Cited 30 times

Online Publication Date: 22 October 2008

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Self-diffusion in intrinsic single crystalline germanium was investigated between 429 and 596 °C using 70Ge/natGe isotope multilayer structures. The diffusivities were determined by neutron reflectometry from the decay of the first and third order Bragg peak. At high temperatures the diffusivities are in excellent agreement with literature data obtained by ion beam sputtering techniques, while considerably smaller diffusion lengths between 0.6 and 4.1 nm were measured. At lower temperatures the accessible range of diffusivities could be expanded to D ≈ 1×10−25 m2 s−1, which is three orders of magnitude lower than the values measured by sputtering techniques. Taking into account available data on Ge self-diffusion, the temperature dependence is accurately described over nine orders of magnitude by a single Arrhenius equation. A diffusion activation enthalpy of 3.13±0.03 eV and a pre-exponential factor of 2.54×10−3 m2 s−1 for temperatures between 429 and 904 °C are obtained. Single vacancies are considered to prevail self-diffusion in Ge over the whole temperature range.
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66.30.H- Self-diffusion and ionic conduction in nonmetals
68.65.Ac Multilayers
65.40.G- Other thermodynamical quantities
68.65.Cd Superlattices
61.72.jd Vacancies

Surface scattering in metallic nanowires

Xi Chen and R. H. Victora

Appl. Phys. Lett. 93, 162105 (2008); http://dx.doi.org/10.1063/1.3006050 (3 pages) | Cited 2 times

Online Publication Date: 23 October 2008

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Electronic transport with surface scattering in metallic nanowires is studied theoretically based on an atomistic tight-binding approach. It is shown that the mean free path (MFP) strongly depends on the size of the wire and the scattering potential at the surface. In the weak scattering regime, the MFP grows with the wire diameter in an oscillatory manner. A perturbation theory is developed to explain this finite size effect. For narrow wires with small roughness, we show that the surface can be the dominant source of scattering and increases the resistivity well above the bulk value, which will adversely impact the future application of nanowire.
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73.63.-b Electronic transport in nanoscale materials and structures
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.22.-f Electronic structure of nanoscale materials and related systems
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
73.25.+i Surface conductivity and carrier phenomena
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)

The effect of phase separation on the temperature dependent magnetoresistance in perovskite oxide heterojunction

Chun-lian Hu, Kui-juan Jin, Peng Han, Hui-bin Lu, Leng Liao, and Guo-zhen Yang

Appl. Phys. Lett. 93, 162106 (2008); http://dx.doi.org/10.1063/1.3003864 (3 pages) | Cited 5 times

Online Publication Date: 24 October 2008

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The interesting behavior of the magnetoresistance at various temperatures for the heterojunction of La0.9Sr0.1MnO3/SrNb0.01Ti0.99O3 is well explained based on the phase separation scenario. The good agreement between the theoretical and experimental results reveals that the mechanism for the variation in magnetoresistance with temperature and with the magnetic field is the competition between the positive magnetoresistance in the paramagnetic phase caused by the interface effect of the La0.9Sr0.1MnO3/SrNb0.01Ti0.99O3 p-n heterojunction and the negative magnetoresistance in the ferromagnetic phase of the La0.9Sr0.1MnO3 film, respectively.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
75.47.Gk Colossal magnetoresistance
75.47.Lx Magnetic oxides
64.75.-g Phase equilibria

Direct hydrogen gas generation by using InGaN epilayers as working electrodes

J. Li, J. Y. Lin, and H. X. Jiang

Appl. Phys. Lett. 93, 162107 (2008); http://dx.doi.org/10.1063/1.3006332 (3 pages) | Cited 18 times

Online Publication Date: 24 October 2008

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We report on the growth and exploitation of InGaN epilayers as a photoelectrochemical cell (PEC) material for direct generation of hydrogen by splitting water using photoelectrochemical hydrolysis. Under white light illumination, a drastic dependence of the photocurrent density on the In content was observed. Direct hydrogen gas generation by splitting water was accomplished using an n-type InxGa1−xN epilayer with a relatively high In content (x ∼ 0.4) as a working electrode. This demonstration of hydrogen generation by water splitting accomplished using InGaN based PEC is highly encouraging.
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82.47.Jk Photoelectrochemical cells, photoelectrochromic and other hybrid electrochemical energy storage devices
72.40.+w Photoconduction and photovoltaic effects
73.50.Pz Photoconduction and photovoltaic effects
82.45.Fk Electrodes
84.60.-h Direct energy conversion and storage
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Spin transfer torque switching of cobalt nanoparticles

X. J. Wang, H. Zou, and Y. Ji

Appl. Phys. Lett. 93, 162501 (2008); http://dx.doi.org/10.1063/1.3005426 (3 pages) | Cited 4 times

Online Publication Date: 20 October 2008

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Magnetization reversals of cobalt nanoparticles induced by spin transfer torque are demonstrated at 4.2 K by a mechanical point-contact made on a Co/Cu/Co trilayer thin film. The top Co layer ( ∼ 0.5 nm) is discontinuous and consists of isolated cobalt nanoparticles with a diameter of <5 nm. The number of nanoparticles underneath a point contact can be controlled by varying the size of the contact. The characteristics of spin transfer switching are qualitatively different for contacts involving a few particles (5–10) and those involving many particles (40–50).
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Jk Magnetization reversal mechanisms
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Cc Other ferromagnetic metals and alloys

Topological defects in antiferromagnetically coupled multilayers with perpendicular anisotropy

N. S. Kiselev, U. K. Rößler, A. N. Bogdanov, and O. Hellwig

Appl. Phys. Lett. 93, 162502 (2008); http://dx.doi.org/10.1063/1.2993328 (3 pages) | Cited 7 times

Online Publication Date: 21 October 2008

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A rich variety of specific multidomain textures recently observed in antiferromagnetically coupled multilayers with perpendicular anisotropy include regular (equilibrium) multidomain states as well as different types of topological magnetic defects. Within a phenomenological theory we have classified and analyzed the possible magnetic defects in the antiferromagnetic ground state and determine their structures. The calculated magnetic phase diagrams show the existent regions for all types of magnetic defects. Experimental investigations of the remanent states (observed after different magnetic prehistory) in [Co/Pt]/Ru multilayers with wedged Co layers reveal a corresponding succession of different magnetic defect domain types.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.30.Gw Magnetic anisotropy
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Ee Antiferromagnetics

Layered antiferromagnetism with high Neel temperature in the intermetallic compound Mn2Au

Sergii Khmelevskyi and Peter Mohn

Appl. Phys. Lett. 93, 162503 (2008); http://dx.doi.org/10.1063/1.3003878 (3 pages) | Cited 3 times

Online Publication Date: 21 October 2008

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On the basis of earlier experimental studies the intermetallic compound Mn2Au has been characterized as a nonmagnetically ordered material. Here we report the results of first-principles calculations based on local spin-density approximation that describes Mn2Au to have a narrow band ground state with rigid local moments on the Mn sites. Calculations of the interatomic exchange constants based on the magnetic force theorem and a Monte Carlo modeling of the resulting Heisenberg-like Hamiltonian predict a high Neel temperature of ∼ 1600 K. This temperature is considerably higher than for the other known high-temperature antiferromagnetic L10-type Mn based binary alloys used in magnetic storage applications.
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75.30.Et Exchange and superexchange interactions
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Ee Antiferromagnetics
71.20.Be Transition metals and alloys
71.28.+d Narrow-band systems; intermediate-valence solids
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Heteroepitaxial growth and optoelectronic properties of layered iron oxyarsenide, LaFeAsO

Hidenori Hiramatsu, Takayoshi Katase, Toshio Kamiya, Masahiro Hirano, and Hideo Hosono

Appl. Phys. Lett. 93, 162504 (2008); http://dx.doi.org/10.1063/1.2996591 (3 pages) | Cited 41 times

Online Publication Date: 22 October 2008

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The epitaxial thin films of LaFeAsO were fabricated on MgO(001) and mixed-perovskite (La,Sr)(Al,Ta)O3(001) single-crystal substrates by pulsed laser deposition using a Nd-doped yttrium aluminum garnet second harmonic source and a 10 at. % F-doped LaFeAsO disk target. Temperature dependences of the electrical resistivities showed no superconducting transition in the temperature range of 2–300 K and were similar to those of undoped polycrystalline bulk samples. The transmittance spectrum exhibited a clear peak at ∼ 0.2 eV, which is explained by ab initio calculations.
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74.78.Fk Multilayers, superlattices, heterostructures
78.30.-j Infrared and Raman spectra
74.25.F- Transport properties
74.25.Gz Optical properties
81.15.Fg Pulsed laser ablation deposition
61.72.up Other materials

Experimental study of domain wall motion in long nanostrips under the influence of a transverse field

S. Glathe, I. Berkov, T. Mikolajick, and R. Mattheis

Appl. Phys. Lett. 93, 162505 (2008); http://dx.doi.org/10.1063/1.2993329 (3 pages) | Cited 26 times

Online Publication Date: 23 October 2008

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We report the real time study of field driven domain wall (DW) motion in giant magnetoresistance nanostrips under the influence of both longitudinal and transverse fields. We have found clear evidence that transverse fields influence the DW dynamics below and above the Walker field [ N. L. Schryer and L. R. Walker, J. Appl. Phys. 45, 5406 (1974) ] drastically. We show the suppression of the Walker breakdown process and a huge enhancement in DW velocity below the Walker field. The maximum velocity reported here is 4500 m/s.
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75.60.Ch Domain walls and domain structure
75.50.Tt Fine-particle systems; nanocrystalline materials
75.47.De Giant magnetoresistance

Magnetic structure near the Co/NiO(001) interface

Elke Arenholz, Gerrit van der Laan, and Frithjof Nolting

Appl. Phys. Lett. 93, 162506 (2008); http://dx.doi.org/10.1063/1.3005643 (3 pages) | Cited 7 times

Online Publication Date: 23 October 2008

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We investigate the magnetic coupling at the Co/NiO interface using soft x-ray magnetic linear dichroism (XMLD) and circular dichroism taking explicitly into account the recently observed angular dependence of the XMLD with respect to the crystallographic axes. We find that the Co moments are aligned perpendicular to the NiO moments. We discuss the impact of the anisotropic XMLD on the intensity ratio of the two peaks at the Ni L2 edge, which is commonly employed to determine the spin orientation in antiferromagnets using XMLD.
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75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.30.Gw Magnetic anisotropy
75.30.Cr Saturation moments and magnetic susceptibilities

Oxygen vacancy induced re-entrant spin glass behavior in multiferroic ErMnO3 thin films

S. Y. Jang, D. Lee, J.-H. Lee, T. W. Noh, Y. Jo, M.-H. Jung, and J.-S. Chung

Appl. Phys. Lett. 93, 162507 (2008); http://dx.doi.org/10.1063/1.3006325 (3 pages) | Cited 7 times

Online Publication Date: 23 October 2008

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Epitaxial thin films of hexagonal ErMnO3 fabricated on Pt(111)/Al2O3(0001) and yttria-stabilized zirconia(111) substrates exhibited both ferroelectric character and magnetic ordering at low temperatures. As the temperature was reduced, the ErMnO3 films first showed antiferromagnetism. At lower temperatures, the films deposited at lower oxygen partial pressures exhibited spin glass behavior. This re-entrant spin glass behavior was attributed to competition between an antiferromagnetic interaction in the hexagonal geometry and a ferromagnetic interaction caused by a change in Mn valence induced by excess electrons from the oxygen vacancies.
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75.50.Lk Spin glasses and other random magnets
75.50.Ee Antiferromagnetics
75.80.+q Magnetomechanical effects, magnetostriction
77.80.-e Ferroelectricity and antiferroelectricity
61.72.jd Vacancies
75.70.-i Magnetic properties of thin films, surfaces, and interfaces

Geometric dephasing-limited Hanle effect in long-distance lateral silicon spin transport devices

Biqin Huang, Hyuk-Jae Jang, and Ian Appelbaum

Appl. Phys. Lett. 93, 162508 (2008); http://dx.doi.org/10.1063/1.3006333 (3 pages) | Cited 21 times

Online Publication Date: 23 October 2008

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Evidence of spin precession and dephasing (“Hanle effect”) induced by a magnetic field is the only unequivocal proof of spin-polarized conduction electron transport in semiconductor devices. However, when spin dephasing is very strong, Hanle effect in a uniaxial magnetic field can be impossible to measure. Using a silicon device with lateral injector-detector separation of over 2 mm and geometrically induced dephasing making spin transport completely incoherent, we show experimentally and theoretically that Hanle effect can still be measured using a two-axis magnetic field.
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85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields

Photoinduced magnetic softening of perpendicularly magnetized L10-FePt granular films

Z. Xu, X. D. Liu, R. X. Gao, Z. F. Chen, T. S. Lai, H. N. Hu, S. M. Zhou, X. J. Bai, and J. Du

Appl. Phys. Lett. 93, 162509 (2008); http://dx.doi.org/10.1063/1.3007977 (3 pages) | Cited 3 times

Online Publication Date: 23 October 2008

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Ultrafast spin dynamics has for the first time been studied in perpendicular magnetized granular films. For FePt continuous films and FePt–MgO and FePt–Ag granular films with femtosecond laser excitations, the coercivity HC and the saturation Kerr rotation θKS are dramatically reduced, accompanied by a sharp increase in the reflectivity R. Afterward, these physical quantities are slowly recovered. The changes in HC, θKS, and R are all different among FePt, FePt–MgO, and FePt–Ag films. The difference is caused by different film thicknesses and in particular by the surface plasmon resonance of metallic nanoparticles.
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75.70.Ak Magnetic properties of monolayers and thin films
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Jk Magnetization reversal mechanisms
78.20.Ls Magneto-optical effects
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

All oxide ferromagnet/semiconductor epitaxial heterostructures

A. Nielsen, A. Brandlmaier, M. Althammer, W. Kaiser, M. Opel, J. Simon, W. Mader, S. T. B. Goennenwein, and R. Gross

Appl. Phys. Lett. 93, 162510 (2008); http://dx.doi.org/10.1063/1.2998576 (3 pages) | Cited 10 times

Online Publication Date: 24 October 2008

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Oxide based ferromagnet/semiconductor heterostructures offer substantial advantages for spin electronics. We have grown (111) oriented Fe3O4 thin films and Fe3O4/ZnO heterostructures on ZnO(0001) and Al2O3(0001) substrates by pulsed laser deposition. High quality crystalline films with mosaic spread as small as 0.03°, sharp interfaces, and rms surface roughness of 0.3 nm were achieved. Magnetization measurements show clear ferromagnetic behavior of the magnetite layers with a saturation magnetization of 3.2μB/f.u. at 300 K. Our results demonstrate that the Fe3O4/ZnO system is an intriguing and promising candidate for the realization of multifunctional heterostructures.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
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Effect of ferroelastic twin walls on local polarization switching: Phase-field modeling

S. Choudhury, J. X. Zhang, Y. L. Li, L. Q. Chen, Q. X. Jia, and S. V. Kalinin

Appl. Phys. Lett. 93, 162901 (2008); http://dx.doi.org/10.1063/1.2993330 (3 pages) | Cited 2 times

Online Publication Date: 21 October 2008

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Local polarization switching in epitaxial ferroelectric thin films in the presence of ferroelastic domain walls was studied using phase-field approach. The nucleation bias profile across a twin wall was analyzed, and the localization of preferential nucleation sites was established. This analysis was further extended to a realistic domain structure with multiple twin boundaries. It was observed that the local nucleation voltage required for a 180° domain switching is closely related to the number of such local defects.
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77.80.Dj Domain structure; hysteresis
77.80.Fm Switching phenomena
77.22.Ej Polarization and depolarization
77.55.-g Dielectric thin films

Magnetoelectric effect near spin reorientation transition in giant magnetostrictive-aluminum nitride thin film structure

Nicolas Tiercelin, A. Talbi, V. Preobrazhensky, P. Pernod, V. Mortet, K. Haenen, and A. Soltani

Appl. Phys. Lett. 93, 162902 (2008); http://dx.doi.org/10.1063/1.3001601 (3 pages) | Cited 13 times

Online Publication Date: 21 October 2008

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Hybrid giant magnetostrictive-piezoelectric film/film structures exhibiting magnetoelectric (ME) effect associated with a magnetic instability of the spin reorientation transition type are presented. We first present the theoretical study of a clamped beam actuator composed of a piezoelectric layer on a substrate actuated by a magnetostrictive layer. The actuator is a polished 50 μm thick 18×5 mm2 silicon substrate coated by an electrode, aluminum nitride, and magnetostrictive nanostructured layer. A ME coefficient of 30 V Oe−1 cm−1 at a 35 KHz longitudinal resonance was measured. Nonlinear excitation of this mode showed a “nonlinear” dynamic ME coefficient of 4 V Oe−1 cm−1.
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07.07.Tw Servo and control equipment; robots
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
75.47.De Giant magnetoresistance
72.20.My Galvanomagnetic and other magnetotransport effects
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
77.55.-g Dielectric thin films
77.65.-j Piezoelectricity and electromechanical effects

Low-temperature structural and dielectric phenomena in La1/3NbO3 and La1/3TaO3: Comparative study

Andrei N. Salak, Nikolai P. Vyshatko, Dmitry D. Khalyavin, Oleksandr Prokhnenko, and Victor M. Ferreira

Appl. Phys. Lett. 93, 162903 (2008); http://dx.doi.org/10.1063/1.3006331 (3 pages) | Cited 5 times

Online Publication Date: 22 October 2008

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The crystal structures of the perovskites La1/3NbO3 and La1/3TaO3 were studied between 10 and 350 K using high-resolution neutron powder diffraction and compared with their radio-frequency dielectric response over the same temperature range. The structure of La1/3NbO3 remains orthorhombic Cmmm, while La1/3TaO3 undergoes continuous transition from the high-temperature tetragonal P4/mmm to Cmmm phase at about 220 K. This transition is tricritical in nature and accompanied by no dielectric anomaly. In La1/3NbO3, the frequency-dependent peak of the dielectric permittivity is associated with an atypical increase in the lattice parameters below about 80 K.
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61.66.Fn Inorganic compounds
61.50.Ks Crystallographic aspects of phase transformations; pressure effects
64.70.K- Solid-solid transitions
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)

Impact of Kr gas mixing in oxygen plasma etching of ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymer films

Joo-Won Yoon, Shun-ichiro Ohmi, Byung-Eun Park, and Hiroshi Ishiwara

Appl. Phys. Lett. 93, 162904 (2008); http://dx.doi.org/10.1063/1.2970085 (3 pages) | Cited 4 times

Online Publication Date: 23 October 2008

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Oxygen plasma etching characteristics of ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymer films are investigated. It was found in MFM (M: metal; F: ferroelectric) capacitors that plasma damage effects to the ferroelectric properties were insignificant when Au metal masks were used. On the contrary, C-V (capacitance versus voltage) characteristics were significantly degraded in plasma-etched MFIS (I: insulator; S: semiconductor) diodes. The origin of this phenomenon is speculated to be degradation of the SiO2/Si interface by energetic oxygen ions and then mixing of Kr gas to the oxygen plasma is attempted to decrease the plasma damage.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
77.80.-e Ferroelectricity and antiferroelectricity
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.32.Tt Capacitors
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Low-temperature synthesis of Si nanowires using multizone chemical vapor deposition methods

Pengfei Qi, William S. Wong, Huaizhou Zhao, and Dunwei Wang

Appl. Phys. Lett. 93, 163101 (2008); http://dx.doi.org/10.1063/1.2999591 (3 pages) | Cited 6 times

Online Publication Date: 20 October 2008

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With a multitemperature zone chemical vapor deposition reactor, silicon nanowires (SiNWs) were synthesized at temperatures below the Au–Si eutectic point, with Au nanoparticles as the growth seeds. Nanoparticle seeds with diameters less than 60 nm were used to grow NWs at temperatures below 350 °C. A strong dependence on the growth rate with the synthesis temperature and the size of the Au nanoparticle seeds was observed. With 10 nm particles, SiNWs were reproducibly synthesized at a temperature of 290 °C. We suggest that the governing role for the synthesis lies in the diffusion of Si feeding into the growth seeds.
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81.16.-c Methods of micro- and nanofabrication and processing
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)
68.65.La Quantum wires (patterned in quantum wells)
66.30.H- Self-diffusion and ionic conduction in nonmetals
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Stabilization of PbSe quantum dots by ultrathin EuTe and SrTe barrier layers

L. Abtin and G. Springholz

Appl. Phys. Lett. 93, 163102 (2008); http://dx.doi.org/10.1063/1.3000386 (3 pages)

Online Publication Date: 20 October 2008

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Overgrowth of self-assembled quantum dots usually changes their shape and composition due to surface exchange reactions and redistribution of adatoms. As shown for PbSe dots, this can be completely suppressed by covering the dots with ultrathin EuTe or SrTe barrier layers, based on the large EuTe and SrTe binding energies. The model is supported by annealing experiments that show that these barrier layers also suppress the usual coarsening and Ostwald ripening process.
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81.16.Dn Self-assembly
61.72.Cc Kinetics of defect formation and annealing

Synthesis and conductance measurement of periodic arrays of gold nanoparticles

Y. Kakefuda, K. Narita, T. Komeda, S. Yoshimoto, and S. Hasegawa

Appl. Phys. Lett. 93, 163103 (2008); http://dx.doi.org/10.1063/1.3001938 (3 pages) | Cited 5 times

Online Publication Date: 20 October 2008

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We report a formation method and an electrical characterization of aligned arrays of Au nanoparticles ( ∼ 20–40 nm). We synthesized the structure by immersing a substrate vertically into a solvent with nanoparticle and letting the solvent evaporate. The periodicity of the arrays has been controlled in 10–40 μm range by tuning the evaporation rate of solvent. The resistivity shows a drastic decrease ( ∼ 10−4) when annealed at ∼ 170 °C. While it is considerably due to a breakdown of ligands surrounding the Au particles, the large change in conductivity should be used for sensors to examine the interface molecules between Au nanoparticles.
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81.07.Bc Nanocrystalline materials
73.25.+i Surface conductivity and carrier phenomena
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Self-organized metal nanowire arrays with tunable optical anisotropy

A. Toma, D. Chiappe, D. Massabò, C. Boragno, and F. Buatier de Mongeot

Appl. Phys. Lett. 93, 163104 (2008); http://dx.doi.org/10.1063/1.3002319 (3 pages) | Cited 18 times

Online Publication Date: 20 October 2008

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Here we report on the development of an unconventional approach for the physical synthesis of laterally ordered self-organized arrays of metallic nanowires supported on nanostructured dielectric templates. The method, based on a combination of nanoscale patterning of the glass substrate by ion beam sputtering with shadow deposition of the metal nanoparticles, provides a viable alternative to time consuming serial nanopatterning approaches. Far-field optical characterization demonstrates that the nanowire arrays exhibit tunable anisotropic properties in the visible range due to the excitation of localized plasmon resonances.
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78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
73.22.Lp Collective excitations
81.15.Cd Deposition by sputtering
81.16.Rf Micro- and nanoscale pattern formation
81.16.Dn Self-assembly
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)
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