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1 Jan 2008

Volume 103, Issue 1, Articles (01xxxx)

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Kinetic phase diagrams of GaN-based polariton lasers

D. Solnyshkov, H. Ouerdane, and G. Malpuech

J. Appl. Phys. 103, 016101 (2008); http://dx.doi.org/10.1063/1.2822148 (3 pages) | Cited 12 times

Online Publication Date: 3 January 2008

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The simulations of polariton relaxation and Bose condensation in GaN microcavities (both bulk and with quantum wells) are performed by solving semiclassical Boltzmann equations. A complete set of kinetic phase diagrams for the most important parameters is calculated. We show that such cavities can operate as low-threshold polariton lasers at room temperature. The lasing threshold of cavity with quantum wells is found to be about ten times smaller than that of a bulk cavity.
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42.55.Sa Microcavity and microdisk lasers
42.55.Px Semiconductor lasers; laser diodes
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.21.Fg Quantum wells
81.30.Dz Phase diagrams of other materials

Enhanced dielectric response of ZrO2 upon Ti doping and introduction of O vacancies

Gargi Dutta, K. P. S. S. Hembram, G. Mohan Rao, and Umesh V. Waghmare

J. Appl. Phys. 103, 016102 (2008); http://dx.doi.org/10.1063/1.2829777 (3 pages) | Cited 3 times

Online Publication Date: 4 January 2008

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We determine the electronic properties and dielectric response of zirconia (ZrO2) with oxygen vacancies (O vacancies) and Ti doping using first-principles density functional theory calculations based on pseudopotentials and a plane wave basis. We find significantly enhanced static dielectric response in zirconia with Ti doping and introduction of oxygen vacancies. Softening of phonon modes are responsible for the enhanced dielectric response of doped samples compared to pure zirconia.
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77.22.Ch Permittivity (dielectric function)
61.72.up Other materials
61.72.jd Vacancies
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Digital communication using Ge metal-insulator-semiconductor light-emitting diodes and photodetectors

T.-H. Cheng, M. H. Liao, Lingyen Yeh, T.-L. Lee, M.-S. Liang, and C. W. Liu

J. Appl. Phys. 103, 016103 (2008); http://dx.doi.org/10.1063/1.2817537 (3 pages) | Cited 2 times

Online Publication Date: 4 January 2008

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Both Ge light-emitting diodes and photodetectors are demonstrated by using the same metal-insulator-semiconductor (MIS) tunneling structure. A Ge MIS tunneling diode biased at the accumulation region is used as a light-emitting device and a Ge MIS tunneling diode biased at the inversion region is used as a photodetector. The ultrathin gate oxide film used in the MIS tunneling diode was grown by liquid phase deposition at 50 °C to lower the thermal budget. A Ge light-emitting diode has a higher quantum efficiency than a similar Si device (at least one order of magnitude stronger) due to the higher radiative recombination coefficient. With the detection of the Ge MIS photodetector, the data communication in free space is reported and demonstrated for the first time.
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85.60.Jb Light-emitting devices
85.60.Gz Photodetectors (including infrared and CCD detectors)
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Localization of He induced nanovoids in buried Si1−xGex thin films

D. D’Angelo, S. Mirabella, E. Bruno, A. Terrasi, C. Bongiorno, F. Giannazzo, V. Raineri, G. Bisognin, and M. Berti

J. Appl. Phys. 103, 016104 (2008); http://dx.doi.org/10.1063/1.2826994 (3 pages) | Cited 4 times

Online Publication Date: 7 January 2008

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The localization of voids in thin Si1−xGex layers after He+ implantation and thermal annealing is reported. A Si/Si1−xGex multilayer grown onto (001) Si was implanted with He+ in the 10−30 keV range, with fluences from 7×1015 up to 1×1016 cm−2, and annealed at 800 °C for 1 h. Samples were analyzed by transmission electron microscopy, showing void formation only within the two layers containing Ge or at the film/substrate interface. Our results support the idea that the compressive strain in the Si1−xGex layers induces the nucleation of small cavities and the growth of voids by a mechanism where vacancies are stabilized by He.
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61.72.U- Doping and impurity implantation
61.72.Qq Microscopic defects (voids, inclusions, etc.)
62.20.F- Deformation and plasticity
61.72.jd Vacancies
61.72.Cc Kinetics of defect formation and annealing
81.40.Lm Deformation, plasticity, and creep

Effect of nanoscale confinement on the β−α phase transition in Ag2Se

Vincent Leon, Yang Ren, and Marie-Louise Saboungi

J. Appl. Phys. 103, 016105 (2008); http://dx.doi.org/10.1063/1.2822135 (3 pages)

Online Publication Date: 9 January 2008

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The confinement of silver selenide was investigated using mesoporous silica. Results from x-ray diffraction and electron microscopy show that the confined material still exhibits a β−α transition similar to the one that takes place in the bulk crystalline state but with a transition temperature that depends significantly on the confinement conditions. Decreasing the pore size leads to an increase of the transition temperature, opposite to the behavior of the melting point observed in several metallic and organic materials. In the free particles, on the other hand, no size dependence is observed with particle sizes down to 4 nm.
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61.46.-w Structure of nanoscale materials
64.70.K- Solid-solid transitions

Chirality dependence of the adsorption of H2 on 4 Å carbon nanotubes

L. Miao, H. J. Liu, Y. W. Wen, X. Zhou, and C. Z. Hu

J. Appl. Phys. 103, 016106 (2008); http://dx.doi.org/10.1063/1.2829779 (3 pages) | Cited 4 times

Online Publication Date: 11 January 2008

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Density functional calculations and the nudged elastic band technique are used to study the adsorption of H2 on 4 Å single-wall carbon nanotubes. It is found that both the chemical and physical adsorptions of H2 are possible and the calculated adsorption barriers are considerably lower than those of larger diameter nanotubes. There is a strong chirality dependence of the energy barriers, and the (5,0) tube seems to be the best choice for the hydrogen storage among three kinds of 4 Å nanotubes.
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68.43.Mn Adsorption kinetics
61.46.Fg Nanotubes
84.60.-h Direct energy conversion and storage

A succession of relaxor ferroelectric transitions in Ba0.55Sr0.45TiO3

Satyendra Singh, Satendra Pal Singh, and Dhananjai Pandey

J. Appl. Phys. 103, 016107 (2008); http://dx.doi.org/10.1063/1.2827506 (3 pages) | Cited 7 times

Online Publication Date: 15 January 2008

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We present here the results of frequency dependent dielectric, polarization, and powder x-ray powder diffraction studies in the 300–100 K temperature range for Ba0.55Sr0.45TiO3. The dielectric results indicate a succession of three relaxor ferroelectric transitions accompanying the cubic to tetragonal to orthorhombic to rhombohedral phase transitions confirmed by x-ray diffraction studies.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
77.22.Ej Polarization and depolarization
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