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20 Oct 2008

Volume 93, Issue 16, Articles (16xxxx)

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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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