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30 Jul 2001

Volume 79, Issue 5, pp. 557-700

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Strong optical transitions via surface states on Si(001)2×1:H ultrathin films: A theoretical study

Masahiko Nishida

Appl. Phys. Lett. 79, 596 (2001); http://dx.doi.org/10.1063/1.1389068 (3 pages) | Cited 5 times

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Optical transitions via localized surface states on Si(001) ultrathin films terminated by monohydride dimers on both surfaces with 2×1 periodicity are studied by use of the extended Hückel-type nonorthogonal tight-binding method. The calculated oscillator strength between the bottom of the empty surface states and the valence-band maximum is much larger than that for direct band-to-band transitions in films with an ideal dihydride termination on both surfaces. An analysis shows that this strong optical coupling is attributed to a significant s-like character introduced into the surface-state bottom by the formation of the monohydride dimers on the film surface. © 2001 American Institute of Physics.
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78.66.Db Elemental semiconductors and insulators
73.20.At Surface states, band structure, electron density of states
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)

Temperature dependence of photoluminescence of InGaN films containing In-rich quantum dots

Yong-Tae Moon, Dong-Joon Kim, Jin-Sub Park, Jeong-Tak Oh, Ji-Myon Lee, Young-Woo Ok, Hyunsoo Kim, and Seong-Ju Park

Appl. Phys. Lett. 79, 599 (2001); http://dx.doi.org/10.1063/1.1389327 (3 pages) | Cited 34 times

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The temperature dependence of the photoluminescence (PL) of InGaN films, grown by metalorganic chemical vapor deposition, has been investigated. A strained InGaN thin film which contains composition-fluctuated regions shows the so-called S-shaped temperature dependence of the dominant PL peak energy. However, an InGaN thick film which contains quantum dot-like In-rich regions shows a sigmoidal temperature dependence of the dominant PL peak energy, as the result of a transfer of carriers from the band-edge related luminescent centers to quantum dot-like In-rich regions. It is also found that the activation energy for the thermal quenching of PL intensity in the InGaN thick film which contains quantum dot-like In-rich regions is larger than that in the strained InGaN thin film which contains composition-fluctuated regions. © 2001 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.67.Hc Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
68.55.-a Thin film structure and morphology

Implantation-produced structural damage in InxGa1−xN

S. O. Kucheyev, J. S. Williams, J. Zou, S. J. Pearton, and Y. Nakagawa

Appl. Phys. Lett. 79, 602 (2001); http://dx.doi.org/10.1063/1.1388881 (3 pages) | Cited 7 times

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The influence of In content on the accumulation of structural damage in InxGa1−xN films (with x = 0.0–0.2) under heavy-ion bombardment is studied by a combination of Rutherford backscattering/channeling spectrometry and transmission electron microscopy. Results show that an increase in In concentration strongly suppresses dynamic annealing processes and, hence, enhances the buildup of stable lattice disorder in InGaN under ion bombardment, A comparison of the damage buildup behavior and defect microstructure in InGaN with those in GaN is presented. Results of this study may have significant technological implications for estimation and control of implantation-produced damage in InGaN/GaN heterostructures. © 2001 American Institute of Physics.
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61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uj III-V and II-VI semiconductors
68.37.Lp Transmission electron microscopy (TEM)
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
61.85.+p Channeling phenomena (blocking, energy loss, etc.)

Electron-stimulated surface stress relaxation of Si

Tetsuya Narushima, Akiko N. Itakura, Takaya Kawabe, and Masahiro Kitajima

Appl. Phys. Lett. 79, 605 (2001); http://dx.doi.org/10.1063/1.1388029 (3 pages) | Cited 9 times

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We have observed the nonthermal relaxation of surface stress in Si induced by electron irradiation at room temperature. An atomically thin disordered layer was introduced by Ar ion bombardment. The surface stress change during ion bombardment and the following electron irradiation of Si(100) was measured by means of an optical microcantilever technique. We have found that the compressive stress in the Si surface due to disorder induced by ion bombardment was completely relaxed by electron irradiation at low energy. The criterion for complete relaxation is found not to be total energy deposition, but the number of irradiated electrons. © 2001 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
79.20.Kz Other electron-impact emission phenomena

Static analysis of off-axis crystal film growth onto a lattice-mismatched substrate

A. Yamada, P. J. Fons, R. Hunger, K. Iwata, K. Matsubara, and S. Niki

Appl. Phys. Lett. 79, 608 (2001); http://dx.doi.org/10.1063/1.1385801 (3 pages) | Cited 9 times

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The interface construction of tilt growth that is sometimes observed for epilayer growth on a lattice mismatched substrate is modeled on the basis that tilt relieves misfit strain in the epilayer. In this model off-axis misfit accommodation is assumed to be due to only tilt dislocations or tilt dislocations combined with misfit dislocations. The average interval between successive dislocations which are formed along the interface can be estimated using the lattice units of both materials and that of the epilayer in another principal axis direction; the tilt angle can also be calculated geometrically. The tilt angle predicted by this model agrees well with experimental results for several examples of mismatched epilayer growth by molecular-beam epitaxy. The model suggests a method to grow a single domain of stress-free epilayer by using a substrate cut to an angle that allows off-axis fit to the lattice unit of the epilayer. © 2001 American Institute of Physics.
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81.15.Aa Theory and models of film growth
61.72.Bb Theories and models of crystal defects
61.72.Mm Grain and twin boundaries

Deformation behavior and plastic instabilities of ultrafine-grained titanium

D. Jia, Y. M. Wang, K. T. Ramesh, E. Ma, Y. T. Zhu, and R. Z. Valiev

Appl. Phys. Lett. 79, 611 (2001); http://dx.doi.org/10.1063/1.1384000 (3 pages) | Cited 161 times

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Ultrafine-grained (UFG) Ti samples have been prepared using equal channel angular pressing followed by cold rolling and annealing. The deformation behavior of these materials, including strain hardening, strain rate dependence of flow stress, deformation/failure mode, and tensile necking instability, have been systematically characterized. The findings are compared with those for conventional coarse-grained Ti and used to explain the limited tensile ductility observed so far for UFG or nanocrystalline metals. © 2001 American Institute of Physics.
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81.05.Bx Metals, semimetals, and alloys
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Epitaxial nanocrystalline tin dioxide thin films grown on (0001) sapphire by femtosecond pulsed laser deposition

J. E. Dominguez, L. Fu, and X. Q. Pan

Appl. Phys. Lett. 79, 614 (2001); http://dx.doi.org/10.1063/1.1386406 (3 pages) | Cited 24 times

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Nanocrystalline tin dioxide (SnO2) thin films of different thicknesses were fabricated on the (0001) surface of α-Al2O3 (sapphire) using femtosecond pulsed laser deposition. X-ray diffraction and transmission electron microscopy (TEM) analysis revealed that the microstructure of the films strongly depends on the film thickness. The films with a small thickness (<30 nm) are composed of nanosized columnar (100) oriented grains (3–5 nm in diameter) which grow epitaxially on the substrate with three different in-plane grain orientations. The (101) oriented grains (25 nm in diameter) appear when the film thickness becomes larger than a critical value (about 60 nm). The volume fraction of the (101) grains increases with film thickness. Cross-section TEM studies indicated that the (101) oriented grains nucleate on the top of the (100) oriented nanosized grains and show abnormal grain growth driven by surface energy minimization. As a result, the electrical transport properties are strongly dependent on the film thickness. © 2001 American Institute of Physics.
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68.55.A- Nucleation and growth
81.15.Fg Pulsed laser ablation deposition
81.05.Hd Other semiconductors
68.55.-a Thin film structure and morphology
73.61.Le Other inorganic semiconductors
61.72.Mm Grain and twin boundaries

Self-limiting atomic-layer deposition of Si on SiO2 by alternate supply of Si2H6 and SiCl4

Shin Yokoyama, Kenji Ohba, and Anri Nakajima

Appl. Phys. Lett. 79, 617 (2001); http://dx.doi.org/10.1063/1.1389508 (3 pages) | Cited 5 times

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Atomic-layer deposition of Si on SiO2 with a self-limiting growth mode was achieved at substrate temperatures between 355 and 385 °C by means of alternate supply of Si2H6 and SiCl4 gas sources. The growth rate was saturated at 2 ML per cycle at these temperatures and for Si2H6 exposure time over 120 s. The smooth surface (∼0.26 nm in arithmetic average roughness) was obtained under the self-limiting condition irrespective of a film thickness up to 6.5 nm. © 2001 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Sputtered silver oxide layers for surface-enhanced Raman spectroscopy

D. Büchel, C. Mihalcea, T. Fukaya, N. Atoda, J. Tominaga, T. Kikukawa, and H. Fuji

Appl. Phys. Lett. 79, 620 (2001); http://dx.doi.org/10.1063/1.1389513 (3 pages) | Cited 29 times

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We present results of reactively sputtered silver oxide thin films as a substrate material for surface-enhanced Raman spectroscopy (SERS). Herein, we show that deposited layers develop an increasingly strong SERS activity upon photoactivation at 488 nm. A benzoic acid/2-propanol solution was used to demonstrate that the bonding of molecules to SERS active sites at the surface can be followed by investigating temporal changes of the corresponding Raman intensities. Furthermore, the laser-induced structural changes in the silver oxide layers lead to a fluctuating SERS activity at high laser intensities which also affects the spectral features of amorphous carbon impurities. © 2001 American Institute of Physics.
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78.30.-j Infrared and Raman spectra
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.-a Thin film structure and morphology
82.80.Gk Analytical methods involving vibrational spectroscopy
81.15.Cd Deposition by sputtering
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