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7 Nov 2005

Volume 87, Issue 19, Articles (19xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 87, 192502 (2005); http://dx.doi.org/10.1063/1.2128478 (3 pages)

Ki-Suk Lee, SangKook Choi, and Sang-Koog Kim
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Local-strain effects in Si/SiGe/Si islands on oxide

K. N. Chiang, C. H. Chang, and C. T. Peng

Appl. Phys. Lett. 87, 191901 (2005); http://dx.doi.org/10.1063/1.2119430 (3 pages) | Cited 2 times

Online Publication Date: 31 October 2005

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The tensile-strained Si, based on the misfit between Si and SiGe gives high speed and high drive current to the metal-oxide-silicon field effect transistors. In order to achieve the total system minimum energy, the island edge, within some characteristic length, bends upwards giving rise to a distorted lattice, as simulated by the finite element method. The finding indicates that the conventional strain partition rule of Si/SiGe/Si layers used for a large island size (>10 μm) is not adequate for a small island size (<200 nm) due to the significant local-strain effect of the edge lattice distortion. For a small island size, the bending from the edge can significantly affect the strain on the surface of the top Si layer, and a compressive strain or reduced tensile strain occurs at the center of the top Si layer, while the conventional strain partition rule predicts a uniform tensile strain on the top Si layer for any size of Si/SiGe/Si islands.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
68.65.Ac Multilayers
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.40.Jj Elasticity and anelasticity, stress-strain relations

Enhanced deep ultraviolet luminescence from AlGaN quantum wells grown in the three-dimensional mode

B. Borisov, S. Nikishin, V. Kuryatkov, and H. Temkin

Appl. Phys. Lett. 87, 191902 (2005); http://dx.doi.org/10.1063/1.2128485 (3 pages) | Cited 6 times

Online Publication Date: 31 October 2005

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We report a significant improvement in the room temperature cathodoluminescence efficiency of AlGaN quantum wells when the three-dimensional growth mode is induced by reduced flux of ammonia. We interpret this observation in terms of formation of quantum dots of AlGaN in Al0.45Ga0.55N wells. Reflection high electron diffraction images and detailed measurements of the cathodoluminescence intensity, linewidth, and wavelength as a function of growth conditions are consistent with the presence of quantum dots.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.67.Hc Quantum dots
78.67.De Quantum wells
68.65.Fg Quantum wells
68.65.Hb Quantum dots (patterned in quantum wells)

Topological defects and the Staebler-Wronski effect in hydrogenated amorphous silicon

Mao-Hua Du and S. B. Zhang

Appl. Phys. Lett. 87, 191903 (2005); http://dx.doi.org/10.1063/1.2130381 (3 pages) | Cited 2 times

Online Publication Date: 31 October 2005

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We propose that the light-induced formation of topological defects may be the origin of the Staebler-Wronski effect in hydrogenated amorphous silicon. Such defect is characterized by a five- and seven-membered ring pair and two dangling bonds, which can trap mobile H to form a 2H metastable complex. This model shows that the photogeneration of the dangling bonds is the result of the topological transformations, whereas the role of the H is to move the photogenerated dangling bonds away from where they were generated.
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71.55.Cn Elemental semiconductors
72.80.Cw Elemental semiconductors
72.40.+w Photoconduction and photovoltaic effects
61.43.Dq Amorphous semiconductors, metals, and alloys

Damage formation and annealing at low temperatures in ion implanted ZnO

K. Lorenz, E. Alves, E. Wendler, O. Bilani, W. Wesch, and M. Hayes

Appl. Phys. Lett. 87, 191904 (2005); http://dx.doi.org/10.1063/1.2126137 (3 pages) | Cited 32 times

Online Publication Date: 31 October 2005

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N, Ar, and Er ions were implanted into ZnO at 15 K within a large fluence range. The Rutherford backscattering technique in the channeling mode was used to study in situ the damage built-up in the Zn sublattice at 15 K. Several stages in the damage formation were observed. From the linear increase of the damage for low implantation fluences, an upper limit of the Zn displacement energy of 65 eV could be estimated for [0001] oriented ZnO. Annealing measurements below room temperature show a significant recovery of the lattice starting at temperatures between 80 and 130 K for a sample implanted with low Er fluence. Samples with higher damage levels do not reveal any damage recovery up to room temperature, pointing to the formation of stable defect complexes.
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61.72.uj III-V and II-VI semiconductors
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
61.72.Cc Kinetics of defect formation and annealing

Compton scattering of elemental silicon at high pressure

J. S. Tse, D. D. Klug, D. T. Jiang, C. Sternemann, M. Volmer, S. Huotari, N. Hiraoka, V. Honkimäki, and K. Hämäläinen

Appl. Phys. Lett. 87, 191905 (2005); http://dx.doi.org/10.1063/1.2126125 (3 pages) | Cited 2 times

Online Publication Date: 1 November 2005

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The electronic structure of elemental silicon has been studied under high pressure using high-energy Compton scattering utilizing synchrotron radiation. The experiment was realized using a special Laue monochromator and a novel assembly of compound refractive lenses. The extremely good focusing enabled us to utilize a Mao–Bell version of the Merrill–Basset diamond anvil cell with a Be gasket up to a pressure of 20 GPa. After the careful subtraction of background scattering, the Compton profile difference for the metastable Si-XII to the Si-V phase was extracted and compared with the theory. The results clearly demonstrate the feasibility and potential of the Compton scattering technique as a complementary tool in the study of electronic structure of materials under high pressure.
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62.50.-p High-pressure effects in solids and liquids
71.20.Mq Elemental semiconductors
78.70.-g Interactions of particles and radiation with matter

Spontaneous compositional superlattice and band-gap reduction in Si-doped AlxGa1−xN epilayers

M. Gao, Y. Lin, S. T. Bradley, S. A. Ringel, J. Hwang, W. J. Schaff, and L. J. Brillson

Appl. Phys. Lett. 87, 191906 (2005); http://dx.doi.org/10.1063/1.2126127 (3 pages) | Cited 7 times

Online Publication Date: 1 November 2005

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Combined transmission electron microscopy (TEM), x-ray diffraction, and cathodoluminescence spectroscopy measurements of AlxGa1−xN thin films grown by molecular-beam epitaxy reveal spontaneous modulation, phase separation, and band-gap reductions that vary systematically with AlN mole fraction across the full alloy series. At low AlN mole fraction (x ⩽ 0.5), AlGaN epilayers display pronounced phase separation. With increasing AlN mole fraction, phase separation is strongly suppressed by the formation of spontaneous modulation, which high spatial resolution TEM techniques unambiguously determine to be an atomic-scale compositional superlattice. Superlattice-induced reductions from band gaps expected for compositionally disordered epilayers exceed several hundred meV for the Al-rich average alloy composition.
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71.20.Nr Semiconductor compounds
78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Fd III-V semiconductors
64.75.-g Phase equilibria

Solid-solid phase transformation via internal stress-induced virtual melting: Additional confirmations

Valery I. Levitas, Laura B. Smilowitz, Bryan F. Henson, and Blaine W. Asay

Appl. Phys. Lett. 87, 191907 (2005); http://dx.doi.org/10.1063/1.2126795 (3 pages) | Cited 3 times

Online Publication Date: 1 November 2005

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Recently, we predicted a mechanism of solid-solid phase transformation (PT) via virtual melting at 121 K below the melting temperature. We report additional experimental and theoretical results for PTs among three polymorphs of the energetic material HMX, α, β, and δ that support this mechanism. In particular: (a) the predicted velocity of interface propagation for β→δ PT and overall kinetics of δ→β PT are in agreement with experiment; (b) the energy of internal stresses is sufficient to reduce the melting temperature from 520 to 400 K for δ→β PT; (c) the nanocracking that appears during solidification does not change the PT thermodynamics and kinetics for the first and the second β↔δ PT cycles; (d) δ→β PT starts at a very small driving force; (e) δ→α and α→δ PTs do not occur above 400 K and below 461 K, respectively.
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64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder

Optical properties of the BaMgAl10O17:Eu2+ phosphor coated with SiO2 for a plasma display panel

I. Y. Jung, Y. Cho, S. G. Lee, S. H. Sohn, D. K. Kim, D. K. Lee, and Y. M. Kweon

Appl. Phys. Lett. 87, 191908 (2005); http://dx.doi.org/10.1063/1.2103400 (3 pages) | Cited 30 times

Online Publication Date: 1 November 2005

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In order to improve the luminance of blue emission of the plasma display panel (PDP), BaMgAl10O17:Eu2+ (BAM) phosphors were synthesized and were coated with SiO2. It was revealed that the surface coating of phosphors with SiO2 leads to an increase in luminance intensity of PDP devices. This seems to be due to the increase of the excitation light which is transmitted into the phosphor, i.e., an effective vacuum ultraviolet absorption of the phosphor via SiO2. The experimental results suggest that the surface coating of BAM with SiO2a is a way to improve the luminance of the PDP.
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78.55.Hx Other solid inorganic materials
52.75.-d Plasma devices
85.60.Pg Display systems
81.65.-b Surface treatments

High-contrast vertical alignment of lateral difluoro-terphenyl liquid crystals

Chien-Hui Wen, Sebastian Gauza, and Shin-Tson Wu

Appl. Phys. Lett. 87, 191909 (2005); http://dx.doi.org/10.1063/1.2128068 (3 pages) | Cited 10 times

Online Publication Date: 2 November 2005

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A simple method for achieving high-contrast vertical alignment of lateral difluoro-terphenyl liquid crystals using buffed polyimide substrates is demonstrated. By doping a positive, nonpolar or negative dielectric anisotropic compound or mixture to the host terphenyl liquid crystals, an excellent vertical alignment is obtained. This alignment is stable throughout the entire nematic range. The selected dopants not only improve the contrast ratio but enhance the figure-of-merit of the host terphenyl mixture as well. This alignment method is particularly useful for high-contrast liquid crystal televisions.
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61.30.-v Liquid crystals
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
77.22.Ch Permittivity (dielectric function)

Hydrogen implantation into ZnO for n+-layer formation

E. V. Monakhov, J. S. Christensen, K. Maknys, B. G. Svensson, and A. Yu. Kuznetsov

Appl. Phys. Lett. 87, 191910 (2005); http://dx.doi.org/10.1063/1.2128059 (3 pages) | Cited 12 times

Online Publication Date: 2 November 2005

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Bulk ZnO crystals were implanted using 100 keV H+ ions with doses 5×1016 and 2×1017 cm−2 and subsequently annealed at 200–600 °C to study the evolution of the implanted H by employing secondary ion mass spectrometry and scanning spreading resistance microscopy. It is shown that the heat treatment results in a decrease of H concentration in the implanted region, while no significant broadening of the H profiles is observed. This suggests that the implanted H is trapped in immobile complexes which dissociate during annealing with subsequent outdiffusion of H from the implanted region. The formation of a highly conductive n+-layer is observed in the implanted region, and the n+-layer is found to be stable up to 600 °C. A correlation between electrical activity of H and presence of radiation damage is discussed.
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61.72.up Other materials
61.82.Fk Semiconductors
61.80.Jh Ion radiation effects
66.30.J- Diffusion of impurities
72.80.Ey III-V and II-VI semiconductors
72.20.-i Conductivity phenomena in semiconductors and insulators
61.72.Cc Kinetics of defect formation and annealing
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Effect of heavy boron doping on pressure-induced phase transitions in single-crystal silicon

X. Q. Yan, X. M. Huang, S. Uda, and M. W. Chen

Appl. Phys. Lett. 87, 191911 (2005); http://dx.doi.org/10.1063/1.2120920 (3 pages) | Cited 11 times

Online Publication Date: 3 November 2005

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The influence of applied loads and loading/unloading rates on pressure-induced phase transitions in lightly and heavily boron-doped silicon was systematically investigated. The resultant phases were plotted into two-dimensional maps with applied loads and loading/unloading rates as the coordinate axes. The formation region of the amorphous phase in the heavily boron-doped silicon was found to be much larger than that in the lightly boron-doped one, suggesting that heavy boron doping promotes the amorphization in silicon.
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61.72.uf Ge and Si
64.70.K- Solid-solid transitions
61.43.Dq Amorphous semiconductors, metals, and alloys
62.50.-p High-pressure effects in solids and liquids

Atomistic study of the dissolution of small boron interstitial clusters in c-Si

Marco Cogoni, Alessandro Mattoni, Blas P. Uberuaga, Arthur F. Voter, and Luciano Colombo

Appl. Phys. Lett. 87, 191912 (2005); http://dx.doi.org/10.1063/1.2130385 (3 pages) | Cited 10 times

Online Publication Date: 4 November 2005

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The dissolution of boron-interstitial clusters (BICs) in crystalline silicon, often formed after ion implantation, is investigated by temperature accelerated dynamics of their formation using the Si–B Stillinger-Weber potential. We find that the dominant breakup event for small BICs is the emission of either Si mono- or di-interstitials, though the dominant reaction for the reactivation of boron is via emission of a boron interstitial defect B1I1. Most reactions are well approximated by the assumption that they are diffusion limited. Finally, the rate limiting step for breakup of clusters with three B atoms involves the B3I2 cluster, which also dissolves via emission of B1I1.
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66.30.Lw Diffusion of other defects
61.72.uf Ge and Si
64.75.-g Phase equilibria
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