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2 Apr 2001

Volume 78, Issue 14, pp. 1961-2084

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The role of high-temperature island coalescence in the development of stresses in GaN films

T. Böttcher, S. Einfeldt, S. Figge, R. Chierchia, H. Heinke, D. Hommel, and J. S. Speck

Appl. Phys. Lett. 78, 1976 (2001); http://dx.doi.org/10.1063/1.1359780 (3 pages) | Cited 80 times

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The formation of dislocations and stress in GaN layers grown by metalorganic vapor phase epitaxy on sapphire is investigated with regard to the average grain diameter. The grain diameter was determined by monitoring the high-temperature GaN island coalescence process during growth using reflectometry. It is found that the density of edge threading dislocations decreases and the compressive stress measured after cooling to room temperature increases when the coalescence thickness and the grain diameter increase. The data are consistent with models of development of tensile stress due to island coalescence during growth. © 2001 American Institute of Physics.
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81.05.Ea III-V semiconductors
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Kk Vapor phase epitaxy; growth from vapor phase
62.20.-x Mechanical properties of solids
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Temperature dependence of near ultraviolet photoluminescence in ZnO/(Mg, Zn)O multiple quantum wells

T. Makino, N. T. Tuan, H. D. Sun, C. H. Chia, Y. Segawa, M. Kawasaki, A. Ohtomo, K. Tamura, T. Suemoto, H. Akiyama, M. Baba, S. Saito, T. Tomita, and H. Koinuma

Appl. Phys. Lett. 78, 1979 (2001); http://dx.doi.org/10.1063/1.1357451 (3 pages) | Cited 46 times

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We report on temperature dependence of excitonic photoluminescence (PL) from ZnO/(Mg, Zn)O multiple quantum wells (MQWs). Two kinds of MQWs having different barrier heights grown by laser molecular-beam epitaxy showed significantly different temperature dependences of PL spectra; in ZnO/Mg0.27Zn0.73O MQWs, the PL peak energy at 50–200 K was a monotonically increasing function of temperature, which was opposite to that ascribed by band gap shrinkage. Moreover, spectra taken at 95–200 K encompassed two peaks, both of which originated from recombination of localized excitons. The temperature-induced shift (redshift-blueshift-peak duplication-redshift) at 5–300 K is caused by a change in the exciton dynamics with increasing temperature due to inhomogeneity and the exciton localization effect. On the other hand, the corresponding dependence in ZnO/Mg0.12Zn0.88O MQWs (lower barrier height) was similar to that in bulk II–VI semiconductors. © 2001 American Institute of Physics.
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78.67.De Quantum wells
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena
73.21.Hb Quantum wires

Ultraviolet-extended real-time spectroscopic ellipsometry for characterization of phase evolution in BN thin films

J. A. Zapien, R. Messier, and R. W. Collins

Appl. Phys. Lett. 78, 1982 (2001); http://dx.doi.org/10.1063/1.1358367 (3 pages) | Cited 9 times

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Real-time spectroscopic ellipsometry with an ultraviolet-extended spectral range (1.5–6.5 eV) has been applied to investigate the sputter deposition of boron nitride (BN) thin films with high cubic content in terms of a two-layer optical model. In this model, the inner and outer layers represent sp2- and sp3-bonded BN (hBN and cBN), respectively. The thickness evolution of the two layers as well as their dielectric functions over the extended spectral range have been determined. © 2001 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.40.Fy Semiconductors
78.47.-p Spectroscopy of solid state dynamics
68.55.Nq Composition and phase identification
81.15.Cd Deposition by sputtering

Elastic properties of Pd40Cu30Ni10P20 bulk glass in supercooled liquid region

N. Nishiyama, A. Inoue, and J. Z. Jiang

Appl. Phys. Lett. 78, 1985 (2001); http://dx.doi.org/10.1063/1.1359490 (3 pages) | Cited 35 times

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In situ ultrasonic measurements for the Pd40Cu30Ni10P20 bulk glass in three states: Glassy solid, supercooled liquid, and crystalline, have been performed. It is found that velocities of both longitudinal and transverse waves and elastic moduli (shear modulus, bulk modulus, Young’s modulus, and Lamé parameter), together with Debye temperature, gradually decrease with increasing temperature through the glass transition temperature as the Poisson’s ratio increases. The behavior of the velocity of transverse wave vs. temperature in the supercooled liquid region could be explained by viscosity flow, rather than the two different crystallization processes in the region, suggested in the literature. No decomposition was detected at a temperature only 5 K below the crystallization temperature. © 2001 American Institute of Physics.
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64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
61.43.Fs Glasses
61.25.Mv Liquid metals and alloys
62.20.D- Elasticity
62.60.+v Acoustical properties of liquids
62.65.+k Acoustical properties of solids

Surfactant mediated growth of MnSi1.7 on Si(001)

S. Teichert, H. Hortenbach, and H.-J. Hinneberg

Appl. Phys. Lett. 78, 1988 (2001); http://dx.doi.org/10.1063/1.1361102 (3 pages) | Cited 9 times

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Sb is used as a surfactant for the growth of MnSi1.7 by reactive deposition of Mn on Si(001). It is found that the presence of Sb during the growth strongly increases the island density and changes the crystalline orientation of the MnSi1.7. The morphology and structure of the resulting silicide are the same both for the deposition of Mn only on a Sb-terminated Si(001) surface and for the codeposition of Mn and Sb on Si(001). A residual Sb coverage close to one monolayer at the sample surface has been determined for both of the preparation conditions. © 2001 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.Hd Other semiconductors

Thermally poled silica samples are structurally heterogeneous: Electron diffraction evidence of partial crystallization

C. Cabrillo, F. J. Bermejo, J. M. Gibson, J. A. Johnson, D. Faccio, V. Pruneri, and P. G. Kazansky

Appl. Phys. Lett. 78, 1991 (2001); http://dx.doi.org/10.1063/1.1359776 (3 pages) | Cited 10 times

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Large structural modifications in v-SiO2 are found to be induced by “thermal poling,” a treatment which makes the glass act as a frequency doubler of an impinging infrared light. The electron diffraction patterns of poled silica plates reveal the presence of a large amount (of order 10%) of crystallites showing patterns consistent with partial crystallization of the glassy matrix into the cristobalite polymorph of silica. © 2001 American Institute of Physics.
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61.43.Fs Glasses
42.70.Ce Glasses, quartz
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Red photoluminescence of gold island films

Leonid Khriachtchev, Lauri Heikkilä, and Tom Kuusela

Appl. Phys. Lett. 78, 1994 (2001); http://dx.doi.org/10.1063/1.1359491 (3 pages) | Cited 21 times

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We comparatively study photoluminescence and morphology of gold films prepared with a sputtering method. The ultrathin films (⩽10 nm) efficiently emit light above 600 nm, which dramatically differs from the known emission of thick gold films. The absorption mechanism in ultrathin gold films is presumably contributed by their island structure promoting interacting plasmons. The collective plasmon states of island films decay radiatively, producing the extraordinary red emission observed under excitation at 488.0, 514.5, and 632.8 nm. The red photoluminescence of ultrathin films is substrate dependent, and correlates with the surface morphology analyzed by using atomic force microscopy and resistance measurements. © 2001 American Institute of Physics.
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78.66.Bz Metals and metallic alloys
78.55.Hx Other solid inorganic materials
68.55.-a Thin film structure and morphology
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
68.35.B- Structure of clean surfaces (and surface reconstruction)
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