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17 Oct 2011

Volume 99, Issue 16, Articles (16xxxx)

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Appl. Phys. Lett. 99, 163301 (2011); http://dx.doi.org/10.1063/1.3651509 (3 pages)

Jonathan E. Allen, Kevin G. Yager, Htay Hlaing, Chang-Yong Nam, Benjamin M. Ocko, and Charles T. Black
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Dresselhaus field-induced anisotropic spin propagation in ZnSe/BeTe type-II quantum wells

H. Mino, S. Yonaiyama, K. Ohto, and R. Akimoto

Appl. Phys. Lett. 99, 161901 (2011); http://dx.doi.org/10.1063/1.3651758 (3 pages) | Cited 1 time

Online Publication Date: 17 October 2011

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The dynamics of photo-injected electrons and the propagation of photo-created spins in nondoped ZnSe/BeTe type-II quantum wells were investigated by time-resolved photo-induced circular dichroism microscopy at room temperature. Spin propagation from the pump spot presents a directionally dependent spin precession frequency in a magnetic field in Voigt configuration. This anisotropic spin propagation is ascribed to the Dresselhaus effect (G. Dresselhaus, Phys. Rev. 100, 580, 1955) on the radially diffusing photo-injected electrons, since the anisotropy depends on both the directions of crystallographic axis and magnetic field.
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78.20.Ls Magneto-optical effects
81.05.Dz II-VI semiconductors
78.67.De Quantum wells
78.47.D- Time resolved spectroscopy (>1 psec)
78.20.Fm Birefringence
81.07.St Quantum wells

Fragility of iron-based glasses

Jong Hyun Na, Marios D. Demetriou, and William L. Johnson

Appl. Phys. Lett. 99, 161902 (2011); http://dx.doi.org/10.1063/1.3651763 (3 pages) | Cited 5 times

Online Publication Date: 17 October 2011

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The viscosity of various iron-based bulk-glass-forming liquids is measured around the glass transition, and the associated fragility is calculated. Fragility is found to vary broadly between compositions, from a low value of ∼43, which indicates fairly “strong” liquid behavior, to ∼65, well within the region of “fragile” behavior. Despite a strong covalent bonding identified in the structure of this class of metal/metalloid glasses, their liquid fragility can be remarkably high, exceeding even the very fragile palladium and platinum bulk-glass formers. An inverse correlation between glass-forming ability and fragility is identified, suggesting that iron-based glasses are effectively “kinetically” stabilized.
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64.70.pe Metallic glasses
61.43.Fs Glasses
66.20.-d Viscosity of liquids; diffusive momentum transport

Temperature dependent energy level shifts of nitrogen-vacancy centers in diamond

X.-D. Chen, C.-H. Dong, F.-W. Sun, C.-L. Zou, J.-M. Cui, Z.-F. Han, and G.-C. Guo

Appl. Phys. Lett. 99, 161903 (2011); http://dx.doi.org/10.1063/1.3652910 (3 pages) | Cited 5 times

Online Publication Date: 18 October 2011

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Magnetic resonance and fluorescence spectra of nitrogen-vacancy (NV) color centers ensemble in high purity diamond sample were measured, with temperature ranging from 5.6 K to 295 K. Both microwave and optical transition energies have similar nonlinear temperature dependent changes, which might mainly originate from the local thermal expansion. As the frequency shifts will reduce the fidelity of resonant quantum control, the present results demonstrate the necessity of taking temperature fluctuation into consideration. For temperature below 100 K, the transition energies show tendencies to be constant, which indicate higher stability and performance in applications with NV centers.
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61.72.jd Vacancies
78.55.Hx Other solid inorganic materials
61.72.jn Color centers
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
71.20.Tx Fullerenes and related materials; intercalation compounds
76.70.Hb Optically detected magnetic resonance (ODMR)

Three-photon near-infrared quantum splitting in β-NaYF4:Ho3+

D. C. Yu, X. Y. Huang, S. Ye, M. Y. Peng, Q. Y. Zhang, and L. Wondraczek

Appl. Phys. Lett. 99, 161904 (2011); http://dx.doi.org/10.1063/1.3652916 (3 pages) | Cited 6 times

Online Publication Date: 18 October 2011

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We report on three-step sequential three-photon near-infrared (NIR) quantum splitting in β-NaYF4:Ho3+, where one absorbed ultraviolet photon is split into three NIR photons with wavelengths 850, 1015, and 1180 nm. The underlying mechanism is analyzed by static and dynamic photoemission and excitation spectroscopy. An internal quantum yield of 124% is estimated on the basis experimental data and theoretical considerations. Further development of an efficient triply splitting NIR phosphor might open up an approach in achieving efficient photonic devices, which enables more photons emitted than absorbed in the excitation process.
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78.55.Hx Other solid inorganic materials
79.60.-i Photoemission and photoelectron spectra

Anisotropic response of nanosized bismuth films upon femtosecond laser excitation monitored by ultrafast electron diffraction

Ahmed R. Esmail and Hani E. Elsayed-Ali

Appl. Phys. Lett. 99, 161905 (2011); http://dx.doi.org/10.1063/1.3652919 (3 pages) | Cited 1 time

Online Publication Date: 18 October 2011

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The lattice response of 5 nm thick bismuth film to femtosecond laser excitation is probed by ultrafast electron diffraction. The transient decay time after laser excitation is greater for diffraction from (012) lattice planes compared to (110) planes and is reduced for both planes with the increased laser fluence. These results indicate that different energy coupling mechanisms to the lattice occur depending on the crystal direction. The behavior of the diffraction peak width indicates partial disorder of the film upon photoexcitation that increases together with the laser fluence.
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63.20.Ry Anharmonic lattice modes
68.55.aj Insulators
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

In situ x-ray study of the formation of defects in Ge islands on Si(001)

M.-I. Richard, T. U. Schülli, and G. Renaud

Appl. Phys. Lett. 99, 161906 (2011); http://dx.doi.org/10.1063/1.3654153 (3 pages) | Cited 1 time

Online Publication Date: 19 October 2011

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Plastic relaxation and formation of defects is a crucial issue in the epitaxial growth of nanoparticles and thin films. Here, we report an in situ non-destructive method based on x-ray diffuse scattering close to forbidden reflections to study the formation of defects during the growth of Ge islands on Si(001). The dependence of in-plane spacing between interfacial dislocations, defect size, and density is analyzed as a function of Ge-deposit. It is found that the introduction of additional defects is preferred to relieve strain during growth.
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81.70.-q Methods of materials testing and analysis
61.72.Lk Linear defects: dislocations, disclinations
78.70.Ck X-ray scattering

Hug-like island growth of Ge on strained vicinal Si(111) surfaces

L. Persichetti, R. Menditto, A. Sgarlata, M. Fanfoni, and A. Balzarotti

Appl. Phys. Lett. 99, 161907 (2011); http://dx.doi.org/10.1063/1.3655906 (3 pages) | Cited 2 times

Online Publication Date: 19 October 2011

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We examine the structure and the evolution of Ge islands epitaxially grown on vicinal Si(111) surfaces by scanning tunneling microscopy. Contrary to what is observed on the singular surface, three-dimensional Ge nanoislands form directly through the elastic relaxation of step-edge protrusions during the unstable step-flow growth. As the substrate misorientation is increased, the islands undergo a shape transformation which is driven by surface energy minimization and controlled by the miscut angle. Using finite element simulations, we show that the dynamics of islanding observed in the experiment results from the anisotropy of the strain relaxation.
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81.05.Cy Elemental semiconductors
81.07.Bc Nanocrystalline materials
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
68.35.Md Surface thermodynamics, surface energies

Effect of the Ti molar ratio on the electrical characteristics of titanium-indium-zinc-oxide thin-film transistors fabricated by using a solution process

Ho Yong Chong, Kyu Wan Han, Young Soo No, and Tae Whan Kim

Appl. Phys. Lett. 99, 161908 (2011); http://dx.doi.org/10.1063/1.3655197 (3 pages) | Cited 6 times

Online Publication Date: 20 October 2011

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Thin film transistors (TFTs) utilizing TiInZnO (TIZO) channel layers with different Ti molar ratios were fabricated by using a solution process. X-ray photoelectron spectroscopy spectra for the TIZO film exhibited that the Ti 2p1/2 peak intensity increased with increasing Ti molar ratio. The addition of the Ti atoms in the TIZO films changed their carrier concentration due to the decrease of O2− ions, resulting in a positive shift of the threshold voltage and in a decrease of the off-current. The on/off current ratio of the TFTs with a 10% Ti molar ratio was as large as 0.21 × 107.
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85.30.Tv Field effect devices
72.20.Fr Low-field transport and mobility; piezoresistance
79.60.Dp Adsorbed layers and thin films

Observation of the Plateau-Rayleigh capillary instability in multi-material optical fibers

S. Shabahang, J. J. Kaufman, D. S. Deng, and A. F. Abouraddy

Appl. Phys. Lett. 99, 161909 (2011); http://dx.doi.org/10.1063/1.3653247 (3 pages) | Cited 4 times

Online Publication Date: 21 October 2011

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We report the observation of the Plateau-Rayleigh capillary instability during the tapering of a multi-material optical fiber. The fiber core is a glass, and the cladding is an amorphous polymer. The instability is manifested in the breakup of the core into a periodic string of size-tunable micro-scale droplets embedded along the fiber axis. The particle diameters may be tuned in the 1–20 μm range through control of the tapering speed and temperature. Extending this approach to the fabrication of polymer and glass nanoparticles appears feasible.
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42.81.Bm Fabrication, cladding, and splicing
42.70.Ce Glasses, quartz
42.70.Jk Polymers and organics
47.55.nb Capillary and thermocapillary flows
47.85.Dh Hydrodynamics, hydraulics, hydrostatics
47.20.-k Flow instabilities
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