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4 Dec 2006

Volume 89, Issue 23, Articles (23xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 89, 233120 (2006); http://dx.doi.org/10.1063/1.2402115 (3 pages)

S. Yeo, Y. Horibe, S. Mori, C. M. Tseng, C. H. Chen, A. G. Khachaturyan, C. L. Zhang, and S.-W. Cheong
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Cathodoluminescence investigations of GaInNAs on GaAs(111)B

J. Miguel-Sánchez, U. Jahn, A. Guzmán, and E. Muñoz

Appl. Phys. Lett. 89, 231901 (2006); http://dx.doi.org/10.1063/1.2398919 (3 pages)

Online Publication Date: 4 December 2006

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In this work, we present a detailed cathodoluminescence characterization of GaInNAs quantum wells grown on GaAs(111)B. As-grown and annealed InGaAs and GaInNAs quantum wells were maeasured and compared by spatially resolved cathodoluminescence at different photon energies. In the case of GaInNAs quantum wells, an increase of the luminescence intensity, a blueshift, and an increment of the modulation depth of intensity profiles were found after rapid thermal annealing cycles. The latter is caused by the presence of nonradiative areas above the GaInNAs quantum well due to stacking faults formed during the growth.
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81.05.Ea III-V semiconductors
81.07.St Quantum wells
78.67.De Quantum wells
78.60.Hk Cathodoluminescence, ionoluminescence
61.72.Cc Kinetics of defect formation and annealing
61.72.Nn Stacking faults and other planar or extended defects

Facile strategy and mechanism for orthorhombic SnO2 thin films

Zhiwen Chen, Joseph K. L. Lai, and Chan-Hung Shek

Appl. Phys. Lett. 89, 231902 (2006); http://dx.doi.org/10.1063/1.2399352 (3 pages) | Cited 10 times

Online Publication Date: 4 December 2006

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Orthorhombic phase SnO2 is a material with unknown optical, electrical, and gas-sensing properties. It was found previously only at high pressures and temperatures. A facile strategy for the synthesis of orthorhombic SnO2 is of fundamental importance. Using pulsed-laser deposition, the authors report a kind of experimental realization of a pure orthorhombic SnO2 thin film under low pressure and temperature that are much lower than those of traditional methods. The optical properties of an orthorhombic SnO2 thin film were measured by spectrophotometric transmittance. The oxygen exchange reaction mechanism at the grain interfaces was proposed to explain the formation and optical properties of this orthorhombic phase.
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81.15.Fg Pulsed laser ablation deposition
68.55.A- Nucleation and growth
78.66.Li Other semiconductors
81.05.Hd Other semiconductors
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)

Investigation of AlN films grown by molecular beam epitaxy on vicinal Si(111) as templates for GaN quantum dots

M. Benaissa, P. Vennéguès, O. Tottereau, L. Nguyen, and F. Semond

Appl. Phys. Lett. 89, 231903 (2006); http://dx.doi.org/10.1063/1.2399940 (3 pages) | Cited 4 times

Online Publication Date: 4 December 2006

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The use of AlN epitaxial films deposited on vicinal Si(111) as templates for the growth of GaN quantum dots is investigated by transmission electron microscopy and atomic force microscopy. It is found that the substrate vicinality induces both a slight tilt of the AlN (0001) direction with respect to the [111] direction and a step bunching mechanism. As a consequence, a dislocation dragging behavior is observed giving rise to dislocation-free areas well suited for the nucleation of GaN quantum dots.
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81.05.Ea III-V semiconductors
81.07.Ta Quantum dots
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.65.Hb Quantum dots (patterned in quantum wells)

Local environment of a diluted element under high pressure: Zn1−xMnxO probed by fluorescence x-ray absorption spectroscopy

J. Pellicer-Porres, A. Segura, J. F. Sánchez-Royo, J. A. Sans, J. P. Itié, A. M. Flank, P. Lagarde, and A. Polian

Appl. Phys. Lett. 89, 231904 (2006); http://dx.doi.org/10.1063/1.2400109 (3 pages) | Cited 13 times

Online Publication Date: 4 December 2006

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The authors report on x-ray absorption measurements performed on Zn1−xMnxO (x = 0.05,0.25) at the Mn K edge (6539 eV) under high pressure. Mn is found to substitute for Zn both in the low pressure wurtzite phase and in the high pressure rocksalt phase. The Mn–O bond length is determined to be 2.02±0.01 Å at ambient conditions, with a compressibility similar to that of Zn–O in pure ZnO, being dictated by the ZnO crystalline environment. The phase transition is reversible in Zn0.95Mn0.05O, but not in Zn0.75Mn0.25O. The authors demonstrate that fluorescence detected x-ray absorption under high pressure can be used to characterize structural changes around minority elements.
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62.50.-p High-pressure effects in solids and liquids
64.70.K- Solid-solid transitions
78.66.Li Other semiconductors
78.70.Dm X-ray absorption spectra
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials

Methyl monolayers improve the fracture strength and durability of silicon nanobeams

Tuncay Alan, Alan T. Zehnder, Debodhonyaa Sengupta, and Melissa A. Hines

Appl. Phys. Lett. 89, 231905 (2006); http://dx.doi.org/10.1063/1.2400180 (3 pages) | Cited 5 times

Online Publication Date: 4 December 2006

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Monolayer-thick coatings have a significant effect on the fracture strength and durability of 210-nm-thick, smooth ( ∼ 0.4 nm rms roughness), single crystal silicon nanobeams. The initial Weibull fracture strength of beams terminated with a methyl (CH3) monolayer was 18.2 GPa. This strength did not degrade after a 23-day exposure to air. In contrast, beams terminated with a monolayer of hydrogen atoms were initially weaker than methyl-terminated beams, and their strength degraded rapidly in air. After a 23-day air exposure, the strength of H-terminated beams was reduced by at least 30%. Since strength durability is correlated with the oxidation resistance of the monolayers, the degradation of H-terminated beams is attributed to the formation of oxide nuclei that act as local stress concentrators.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.65.Mq Oxidation

Threading dislocation reduction by SiGeC domains in SiGe/SiGeC heterostructure: Role of pure edge dislocations

L. H. Wong, C. Ferraris, C. C. Wong, and J. P. Liu

Appl. Phys. Lett. 89, 231906 (2006); http://dx.doi.org/10.1063/1.2402227 (3 pages)

Online Publication Date: 5 December 2006

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The authors previously reported an unusual phenomenon of strain relaxation accompanied by a reduction in threading dislocation density (TDD) on a Si0.77Ge0.23 layer grown on top of alternating layers of Si0.77Ge0.23/Si0.76Ge0.23C0.01 [ Appl. Phys. Lett. 88, 041915 (2006) ]. In this letter, the mechanism by which SiGeC domains, formed during annealing at 1000 °C, assist in TDD annihilation process is further investigated. A g∙b analysis of transmission electron microscope images showed the formation of pure edge dislocations from the reaction of two 60° misfit dislocations, which glide and/or slip with the assistance of the localized interfacial strain of the SiGeC domains. TDD reduction in this structure is thus due to the annihilation of threading dislocation arms during misfit dislocation combination.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Cc Kinetics of defect formation and annealing

Estimation of minimum electron dose necessary to resolve molecular structure of deoxyribonucleic acid by phase transmission electron microscopy

Tsunenori Nomaguchi, Yoshihide Kimura, and Yoshizo Takai

Appl. Phys. Lett. 89, 231907 (2006); http://dx.doi.org/10.1063/1.2402230 (3 pages) | Cited 4 times

Online Publication Date: 5 December 2006

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The minimum electron dose that is necessary to resolve the molecular structure of deoxyribonucleic acid (DNA) was estimated based on experimental measurements of information limits and simulated DNA images, considering conditions of a low electron dose. From these results, a dose of ∼ 400 e/Å2 was found to be necessary to achieve observation of DNA on a molecular scale under the present experimental setup. A DNA molecule was observed by a phase reconstruction method using through-focus images under the limited electron dose. In the reconstructed images, the helical structure and the intervals of the base pairs of DNA were partially resolved.
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87.64.Ee Electron microscopy
87.14.G- Nucleic acids
87.15.A- Theory, modeling, and computer simulation

Carrier dynamics and electrostatic potential variation in InGaN quantum wells grown on {11math2} GaN pyramidal planes

S. Srinivasan, M. Stevens, F. A. Ponce, H. Omiya, and T. Mukai

Appl. Phys. Lett. 89, 231908 (2006); http://dx.doi.org/10.1063/1.2397566 (3 pages) | Cited 4 times

Online Publication Date: 5 December 2006

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InGaN quantum wells grown in the conventional [0001] direction are known to exhibit long carrier lifetimes that are attributed to strong internal electric fields due to spontaneous and piezoelectric polarization. These fields are expected to be considerably reduced in other crystal geometries. In this work, the authors have investigated the carrier dynamics of InGaN single quantum wells grown parallel to {11math2} planes. The carrier lifetimes, measured by time-resolved cathodoluminescence, are considerably smaller than for quantum wells grown in the conventional c-plane geometry. In addition, the lifetime does not change significantly with varying indium composition or increasing well width. Electron holography measurements of the electrostatic potential across these quantum wells confirm that the internal fields in this geometry are negligible. These results are of interest for the development of higher-efficiency light-emitting diodes using alternative substrate orientations.
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73.63.Hs Quantum wells
78.67.De Quantum wells
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.60.Hk Cathodoluminescence, ionoluminescence
78.47.-p Spectroscopy of solid state dynamics
77.65.-j Piezoelectricity and electromechanical effects

Tunable full-color-emitting La0.827Al11.9O19.09:Eu2+,Mn2+ phosphor for application to warm white-light-emitting diodes

Yu-Ho Won, Ho Seong Jang, Won Bin Im, Duk Young Jeon, and Jeong Soo Lee

Appl. Phys. Lett. 89, 231909 (2006); http://dx.doi.org/10.1063/1.2398887 (3 pages) | Cited 50 times

Online Publication Date: 5 December 2006

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La0.827Al11.9O19.09:Eu2+,Mn2+ showed three emission bands when excited by ultraviolet light. A blue emission originates from Eu2+, whereas both green and red emissions originate from Mn2+. The luminescent mechanism is explained invoking the energy transfer of Eu2+→Mn2+ and Mn2+(tetrahedral site)→Mn2+(octahedral site). This energy transfer was confirmed by faster decay times of the blue and green emissions as energy donors. The emitted color of La0.827Al11.9O19.09:Eu2+,Mn2+ can be easily tailored from blue to red through variations of the Mn2+ content. The white-light-emitting diode fabricated via a combination of an ultraviolet light-emitting diode (λpeak = 385 nm) with La0.827Al11.9O19.09:Eu2+,Mn2+ showed a warm white light (Tc = 3559 K).
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85.60.Jb Light-emitting devices

Complementary analyses on the local polarity in lateral polarity-inverted GaN heterostructure on sapphire (0001) substrate

Ryuji Katayama, Yoshihiro Kuge, Kentaro Onabe, Tomonori Matsushita, and Takashi Kondo

Appl. Phys. Lett. 89, 231910 (2006); http://dx.doi.org/10.1063/1.2398924 (3 pages) | Cited 7 times

Online Publication Date: 5 December 2006

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The fabrication of the lateral polarity-inverted GaN heterostructure on sapphire (0001) using a radio-frequency-plasma-enhanced molecular beam epitaxy is demonstrated. Its microscopic properties such as surface potentials, piezoelectric polarizations, and residual carrier densities were investigated by Kelvin force microscopy and micro-Raman scattering. The inversion from Ga polarity to N polarity in a specific domain and its higher crystal perfection had been unambiguously confirmed by these complementary analyses. The results were also fairly consistent with that of KOH etching, which suggests the applicability of these processes to the fabrication of photonic nanostructures.
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81.05.Ea III-V semiconductors
81.07.-b Nanoscale materials and structures: fabrication and characterization
73.63.-b Electronic transport in nanoscale materials and structures
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
77.65.-j Piezoelectricity and electromechanical effects
77.22.Ej Polarization and depolarization

Photoluminescence properties: Catalyst-free ZnO nanorods and layers versus bulk ZnO

M. Al-Suleiman, A. Che Mofor, A. El-Shaer, A. Bakin, H.-H. Wehmann, and A. Waag

Appl. Phys. Lett. 89, 231911 (2006); http://dx.doi.org/10.1063/1.2399349 (3 pages) | Cited 15 times

Online Publication Date: 5 December 2006

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In this contribution, we compare the photoluminescence properties of ZnO nanorods and epilayers with those of bulk ZnO. Owing to the high aspect ratio (length of 4–14 μm, diameter of 80–500 nm), the characterized ZnO nanorods show very good optical properties. Due to the high surface-to-volume ratio in ZnO nanorods, surface excitons dominate at low temperature. The optical properties of nanorod ensembles improve with increasing nanorod length. The photoluminescence emission from free A excitons was intense in the ZnO layer at 13 K.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.22.Lp Collective excitations

Investigations of GaN surface quantum well in AlGaN/GaN transistor heterostructures by contactless electroreflectance spectroscopy

M. Motyka, M. Syperek, R. Kudrawiec, J. Misiewicz, M. Rudziński, P. R. Hageman, and P. K. Larsen

Appl. Phys. Lett. 89, 231912 (2006); http://dx.doi.org/10.1063/1.2399372 (3 pages) | Cited 7 times

Online Publication Date: 5 December 2006

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AlGaN/GaN transistor heterostructures, caped by ∼ 2 nm GaN layer, were investigated by contactless electroreflectance (CER) spectroscopy at room temperature. Below the AlGaN-related transition CER spectra have shown a clear resonance at the energy of ∼ 3.7 eV, i.e., at much higher energy than the GaN band gap energy. The observed feature has been connected with the optical transition within the GaN cap layer. It was concluded that a surface GaN quantum well has been created by the deposition of nominally undoped (or Si-doped) GaN cap layer on AlGaN/GaN transistor heterostructures.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.30.Tv Field effect devices
81.07.St Quantum wells

Tunable single photonic defect-mode in cholesteric liquid crystals with laser-induced local modifications of helix

Hiroyuki Yoshida, Chee Heng Lee, Akihiko Fujii, and Masanori Ozaki

Appl. Phys. Lett. 89, 231913 (2006); http://dx.doi.org/10.1063/1.2400070 (3 pages) | Cited 10 times

Online Publication Date: 5 December 2006

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The authors demonstrate a tunable single photonic defect-mode in a single cholesteric liquid crystal material based on a structural defect introduced by local modification of the helix. An unpolymerized region of cholesteric liquid crystal acting as the defect was left between two polymerized regions via a two-photon excitation laser-lithography process. Upon polymerization, the cholesteric liquid crystal helix elongated and became thermally stable, and a single photonic defect mode was exhibited due to the contrast in the helix pitch at the defect. The defect mode showed tunability upon heating, and a 36 nm redshift was seen over a temperature range of 30 °C.
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42.70.Df Liquid crystals
61.30.-v Liquid crystals
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
82.35.-x Polymers: properties; reactions; polymerization

Ge/HfNx diffusion barrier for Cu metallization on Si

S. Rawal, D. P. Norton, KeeChan Kim, T. J. Anderson, and L. McElwee-White

Appl. Phys. Lett. 89, 231914 (2006); http://dx.doi.org/10.1063/1.2400071 (3 pages) | Cited 7 times

Online Publication Date: 5 December 2006

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The properties of Ge/HfNx have been investigated relative to its use as a diffusion barrier for Cu metallization. The Ge/HfNx bilayer was grown on p-Si (001) substrates by reactive sputtering, followed by in situ deposition of Cu. Individually annealed films at different temperatures (400–700 °C, 1 h) were characterized for evidence of Cu transport through the barrier bilayer to the Si substrate. The annealed structures were characterized by x-ray diffraction, energy-dispersive spectroscopy, and high-resolution transmission electron microscopy. The results indicate superior diffusion barrier properties of Ge/HfNx for Cu metallization on Si compared to that for HfNx (7 nm).
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68.35.Fx Diffusion; interface formation
73.40.Ns Metal-nonmetal contacts
85.40.Ls Metallization, contacts, interconnects; device isolation
61.72.Cc Kinetics of defect formation and annealing
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
68.37.Lp Transmission electron microscopy (TEM)

Microstructural anisotropy at the ion-induced rippled amorphous-crystalline interface of silicon

S. Grigorian, U. Pietsch, J. Grenzer, D. P. Datta, T. K. Chini, S. Hazra, and M. K. Sanyal

Appl. Phys. Lett. 89, 231915 (2006); http://dx.doi.org/10.1063/1.2402212 (3 pages) | Cited 7 times

Online Publication Date: 6 December 2006

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Using grazing-incidence x-ray scattering technique the authors have investigated the evolution of the damage profile of the transition layer between the ion-induced ripplelike pattern on top surface and the ripples at buried crystalline interface in silicon created after irradiation with 60 keV Ar+ ions under 60°. The transition layer consists of a defect-rich crystalline part and a complete amorphous part. The crystalline regions are highly strained but relaxed for low dose and high dose irradiations, respectively. The appearance of texture in both cases shows that the damage of the initial crystalline structure by the ion bombardment takes place along particular crystallographic directions.
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68.47.Fg Semiconductor surfaces
68.35.Fx Diffusion; interface formation
68.35.Ct Interface structure and roughness
61.72.Dd Experimental determination of defects by diffraction and scattering
61.80.Jh Ion radiation effects
78.70.Ck X-ray scattering

Coherent optical phonons in diamond

Kunie Ishioka, Muneaki Hase, Masahiro Kitajima, and Hrvoje Petek

Appl. Phys. Lett. 89, 231916 (2006); http://dx.doi.org/10.1063/1.2402231 (3 pages) | Cited 18 times

Online Publication Date: 6 December 2006

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The authors report femtosecond dynamics of the coherent optical phonon of single crystal diamond. Sub-10 fs, 395 nm laser pulses excite 40 THz coherent phonons with an extremely small damping rate (0.15 ps−1). Linear power dependence of the phonon amplitude under off-resonant excitation condition gives a direct evidence for an eletric-field-driven generation mechanism. The coherent phonon generation is noticeably suppressed by doping with nitrogen impurities, in spite of their absorption in the near ultraviolet. The present study demonstrates that a simple pump-probe technique can be a powerful tool for evaluating the ultrafast coherent electronic and lattice dynamics of diamond materials.
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63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.47.-p Spectroscopy of solid state dynamics
61.72.up Other materials

Structural characteristics of GaSb/GaAs nanowire heterostructures grown by metal-organic chemical vapor deposition

Y. N. Guo, J. Zou, M. Paladugu, H. Wang, Q. Gao, H. H. Tan, and C. Jagadish

Appl. Phys. Lett. 89, 231917 (2006); http://dx.doi.org/10.1063/1.2402234 (3 pages) | Cited 22 times

Online Publication Date: 6 December 2006

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Highly lattice mismatched (7.8%) GaAs/GaSb nanowire heterostructures were grown by metal-organic chemical vapor deposition and their detailed structural characteristics were determined by electron microscopy. The facts that (i) no defects have been found in GaSb and its interfaces with GaAs and (ii) the lattice mismatch between GaSb/GaAs was fully relaxed suggest that the growth of GaSb nanowires is purely governed by the thermodynamics. The authors believe that the low growth rate of GaSb nanowires leads to the equilibrium growth.
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68.65.La Quantum wires (patterned in quantum wells)
61.46.-w Structure of nanoscale materials
81.07.Vb Quantum wires
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Well-aligned in situ composites in directionally solidified Fe–Ni peritectic system

Yanqing Su, Liangshun Luo, Xinzhong Li, Jingjie Guo, Huimin Yang, and Hengzhi Fu

Appl. Phys. Lett. 89, 231918 (2006); http://dx.doi.org/10.1063/1.2402236 (3 pages) | Cited 6 times

Online Publication Date: 6 December 2006

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Well-aligned in situ composites obtained in directionally solidified Fe–Ni peritectic system are formed by nonisothermal cellular coupled growth instead of isothermal coupled growth because of morphological instabilities. Peritectic coupled growth, with a plane interface like eutectic coupled growth, is always unstable due to the influence of peritectic reaction around the liquid/δ/γ trijunctions. However, cellular nonisothermal peritectic coupled growth, in which one of the two solid phases bulges towards the liquid ahead of the other one, can reach a steady state and produce well-aligned in situ composites under proper growth conditions and sample composition.
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81.30.Fb Solidification
64.70.D- Solid-liquid transitions

Simultaneous determination of indium and nitrogen contents of InGaAsN quantum wells by optical in situ monitoring

O. Reentilä, M. Mattila, M. Sopanen, and H. Lipsanen

Appl. Phys. Lett. 89, 231919 (2006); http://dx.doi.org/10.1063/1.2402265 (3 pages)

Online Publication Date: 6 December 2006

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In situ monitoring of metal-organic vapor phase epitaxial growth of InGaAsN/GaAs multiquantum wells is studied. The complex refractive index of InGaAsN is determined for several indium and nitrogen contents based on the fits to the reflectance curve. Taking advantage of the different effects caused by the incorporation of indium and nitrogen on the complex refractive index of InGaAsN, the InGaAsN quantum well nitrogen and indium contents are simultaneously determined in situ.
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78.30.Fs III-V and II-VI semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Pair distribution function study and mechanical behavior of as-cast and structurally relaxed Zr-based bulk metallic glasses

Cang Fan, P. K. Liaw, T. W. Wilson, H. Choo, Y. F. Gao, C. T. Liu, Th. Proffen, and J. W. Richardson

Appl. Phys. Lett. 89, 231920 (2006); http://dx.doi.org/10.1063/1.2402884 (3 pages) | Cited 5 times

Online Publication Date: 6 December 2006

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Contrary to reported results on structural relaxation inducing brittleness in amorphous alloys, the authors found that structural relaxation actually caused an increase in the strength of Zr55Cu35Al10 bulk metallic glass (BMG) without changing the plasticity. Three dimensional models were rebuilt for the as-cast and structurally relaxed BMGs by reverse Monte Carlo (RMC) simulations based on the pair distribution function (PDF) measured by neutron scattering. Only a small portion of the atom pairs was found to change to more dense packing. The concept of free volume was defined based on the PDF and RMC studies, and the mechanism of mechanical behavior was discussed.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
61.43.Fs Glasses
61.43.Bn Structural modeling: serial-addition models, computer simulation

First principles calculations on martensitic transformation and phase instability of Ni–Mn–Ga high temperature shape memory alloys

Jie Chen, Yan Li, Jiaxiang Shang, and Huibin Xu

Appl. Phys. Lett. 89, 231921 (2006); http://dx.doi.org/10.1063/1.2402891 (3 pages) | Cited 13 times

Online Publication Date: 6 December 2006

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Martensitic transformation and phase instability of Ni8+xMn4Ga4−x high-temperature shape memory alloys have been investigated by first principles calculations using the pseudopotentials plane wave method. The tetragonality (the ratio between the lattice parameter c and a) increases with the increasing of Ni content. The total energy difference between parent and martensite phases plays an important role on the martensitic transformation. The formation energy calculations indicate the instability of Ni–Mn–Ga alloy with extra high Ni content. The densities of states of the alloys are discussed.
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81.30.Kf Martensitic transformations
64.70.K- Solid-solid transitions
61.66.Dk Alloys
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
71.15.Nc Total energy and cohesive energy calculations

Effect of nitrogen doping on optical properties and electronic structures of SrTiO3 films

Y. Y. Mi, S. J. Wang, J. W. Chai, J. S. Pan, C. H. A. Huan, Y. P. Feng, and C. K. Ong

Appl. Phys. Lett. 89, 231922 (2006); http://dx.doi.org/10.1063/1.2403181 (3 pages) | Cited 18 times

Online Publication Date: 6 December 2006

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The nitrogen-doping induced changes in optical properties and electronic structures of SrTiO3 films have been investigated by using spectroscopic ellipsometry and x-ray photoemission spectroscopy. Combined with the first-principles calculations, it is found that the localized N 2p states above O 2p states are attributed to the new absorption edge at 500 nm and the photoactivity in the visible light region. Our results are consistent with both recent experimental and theoretical studies on nitrogen-doped TiO2, where the visible light responses arise from the localized N 2p states slightly above the valence-band edge rather than the band gap narrowing.
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78.66.Nk Insulators
78.40.Ha Other nonmetallic inorganics
71.20.Ps Other inorganic compounds
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.50.Hp Processes caused by visible and UV light
61.72.up Other materials

Surface effects on the diffraction of plane compressional waves by a nanosized circular hole

G. F. Wang, T. J. Wang, and X. Q. Feng

Appl. Phys. Lett. 89, 231923 (2006); http://dx.doi.org/10.1063/1.2403899 (3 pages) | Cited 28 times

Online Publication Date: 6 December 2006

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In the present letter, the authors consider the diffraction of plane harmonic compressional wave (P wave) by a nanosized circular hole. The surface elasticity theory is employed to incorporate the surface effects. The results show that once the radius of hole reduces to nanometers, surface energy significantly affects the diffraction of elastic waves. For incident waves with different frequencies, the influences of surface elasticity on dynamic stress concentration are discussed in details.
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62.25.-g Mechanical properties of nanoscale systems
46.40.Cd Mechanical wave propagation (including diffraction, scattering, and dispersion)
46.40.Jj Aeroelasticity and hydroelasticity
62.30.+d Mechanical and elastic waves; vibrations
68.35.Md Surface thermodynamics, surface energies
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Low temperature chemical vapor deposition of Si-based compounds via SiH3SiH2SiH3: Metastable SiSn/GeSn/Si(100) heteroepitaxial structures

J. Tolle, A. V. G. Chizmeshya, Y.-Y. Fang, J. Kouvetakis, V. R. D’Costa, C.-W. Hu, J. Menéndez, and I. S. T. Tsong

Appl. Phys. Lett. 89, 231924 (2006); http://dx.doi.org/10.1063/1.2403903 (3 pages) | Cited 14 times

Online Publication Date: 6 December 2006

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Growth of Si1−xSnx alloys on Ge1−ySny-buffered Si(100) was achieved via reactions of SnD4 and SiH3SiH2SiH3 at 275 °C. Kinetic studies indicate that unprecedented low growth temperatures are made possible by the highly reactive SiH2 groups. The authors obtain supersaturated metastable compositions (y ∼ 25%) near the indirect to direct band gap crossover predicted by first principles simulations. Extensive characterizations of composition, structure, and morphology show that the SiSn/GeSn films grow lattice matched via a “compositional pinning” mechanism. The initial Raman observations of Si–Sn bond vibrations in a condensed phase are discussed in the context of simulated bond distributions in the alloys.
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68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.30.Er Solid metals and alloys
78.66.Bz Metals and metallic alloys
71.20.Be Transition metals and alloys

Roles of oxygen and water vapor in the oxidation of halogen terminated Ge(111) surfaces

Shiyu Sun, Yun Sun, Zhi Liu, Dong-Ick Lee, and Piero Pianetta

Appl. Phys. Lett. 89, 231925 (2006); http://dx.doi.org/10.1063/1.2403908 (3 pages) | Cited 8 times

Online Publication Date: 6 December 2006

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The initial stage of the oxidation of Cl and Br terminated Ge(111) surfaces is studied using photoelectron spectroscopy. The authors perform controlled experiments to differentiate the effects of different factors in oxidation, and find that water vapor and oxygen play different roles. Water vapor effectively replaces the halogen termination layers with the hydroxyl group, but does not oxidize the surfaces further. In contrast, little oxidation is observed for Cl and Br terminated surfaces with dry oxygen alone. However, with the help of water vapor, oxygen oxidizes the surface by breaking the Ge–Ge back bonds instead of changing the termination layer.
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68.47.Fg Semiconductor surfaces
81.65.Mq Oxidation
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.05.Cy Elemental semiconductors
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