Ultrafast carrier dynamics in p-doped InAs/GaAs Quantum-dot amplifiers

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Magneto-optical Kerr effect, is used to investigate the magnetization of film made of uncoalesced cobalt and cobalt-platinum nanocrystals. For the pure cobalt nanocrystals, different film morphologies are obtained through application of magnetic field during deposition. These morphologies have quite different magnetic properties, which is rationalized by considering dipolar interactions and the associated demagnetizing factor. We show that fast annealing can be used to trigger changes in the particles' crys

Spatially resolved photoluminescence spectra of thin GaAs quantum wells are measured by near-field spectroscopy, and two-energy autocorrelation functions of the spectra are derived. We demonstrate distinctly different autocorrelation functions for a 3-nm-thick quantum well grown on a (311)A surface and for quantum wells grown on (100) substrates. The autocorrelation spectra of the (311)A GaAs quantum well are quantitatively described by a statistical disorder model with a single correlation length of 17 nm

A transmission electron microscopy (TEM) study using weak-beam imaging has been addressed in order to assess the microstructure of NiAl (100) single-crystals subsequently to irradiation at room temperature with 700 keV nickel ions up to 10(15) cm(-2) or 1.5 dpa, namely, defect cluster formation and respective depth distribution. This work shows that the incoming ions undergo channeling along the [100] crystallographic direction and that the actual projected range is approximately 500 nm instead of the 250 n

Optical and transmission electron microscopy have been used to investigate the microdeformation mechanisms in thin films of amorphous semi-aromatic polyamides with different chemical structures and chain lengths. In the chosen range of test temperatures (between 2120 8C and the principal mechanical relaxation temperature, Ta), three successive microdeformation mechanisms were identified: chain scission crazing (CSC) at the lowest temperatures, shear deformation zones (SDZs) at intermediate temperatures and

Relaxor Pb(Sc1/2Nb1/2)O-3 (PSN) thin films without pyrochlore phase were processed from the modified alkoxide solution precursors. The preparation of single phase PSN thin films has a narrow processing window due to the appearance of an undesirable pyrochlore phase and volatility of PbO. Thin film processing has been improved through selection of precursor solutions, heat treatment and optimized deposition-condition are optimized. Especially, the effects of Pt substrates seeded with additional layers upper

We have directly measured, under operating conditions, the distributions of carrier densities and temperatures in a gain-clamped semiconductor optical amplifier designed for operation at 1.55 mum. As expected, longitudinal spatial hole burning is much smaller than in conventional semiconductor optical amplifiers and the effects of gain clamping are clearly evidenced. The amplifier nevertheless shows a sizeable temperature increase for both the lattice and the carriers at high currents, which are attributed

The electronic structure of ex situ grown highly oriented thin films of the quasi-ID organic metal tetrathiafulvalene tetracyanoquinodimethane (TTF-TCNQ) has been characterized by means of temperature-dependent high-resolution angle-resolved photoemission spectroscopy and X-ray photoelectron spectroscopy. Band dispersion near the Fermi level (EF) is observed at low temperatures (similar to 100 K) for as-received samples. At room temperature both charged and neutral TCNQ species (TCNQ(-) and TCNQ(0), respect

We report on efficient, narrow linewidth exciton recombination in GaAs/AlGaAs V-groove quantum wire light-emitting diodes at room temperature. The high efficiency is due to a selective carrier injection mechanism resulting in an estimated internal quantum efficiency of similar to 20% with an electroluminescence (EL) linewidth as narrow as 15 meV. The thermal broadening contribution to the linewidth is 6 meV due to exciton scattering with optical phonons. An analysis of the EL peak shift in a magnetic field

We study the subpicosecond gain dynamics in a high-finesse semiconductor microcavity containing quantum wells by means of degenerate pump-probe spectroscopy. Tuning the optical excitation in resonance with both the exciton and the cavity modes, at high pump fields the probe pulses are strongly amplified near the energy of the empty-cavity mode. At zero probe delay, integration of the probe spectrum yields a net gain of several percents. The coherent nature of the gain is demonstrated by its oscillatory beha

The effects of donor (Nb, Ta) and acceptor (Na, Mg, Fe) dopants on the crystallization mechanism of PZT thin films were investigated. The parameters which control microstructure development were found to be different for donors and accepters. Lead stoichiometry was found to be the critical parameter for donor doped films. Donor substitutions in the perovskite lattice ABO(3), require a compensation by creation of A-site vacancies, Pb1-x/2(Zr,Ti)(1-x) NbxO3, in order to maintain electroneutrality. In the pyro

The title compound, C6H12N4. C9H16O4, undergoes several thermotropic phase transitions. The crystalline structure is layered, with sheets of azelaic acid linked to sheets of hexamethylenetetramine by hydrogen bonds. In the room-temperature phase, the azelaic acid molecules are disordered. By lowering the temperature, this disorder partially disappears. The ordering is clearly observed in reciprocal space where on the rods of diffuse scattering, present in the room-temperature phase, a series of superstructu

An entire microsystem for high accuracy magnetic field measurement based on vertical Hall devices has been simulated. In accordance with existing knowledge about semiconductor physics and experimental results, a functional SPICE- model for a vertical Hall device has been developed. This model was then applied to simulate an existing high accuracy magnetometer, including temperature and non-linearity compensation. The comparison of simulated and measured results shows that the real physical effects as well a

Ultrafast carrier dynamics in p-doped InAs/GaAs Quantum-dot amplifiers

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Magnetic properties of cobalt and cobalt-platinum nanocrystals investigated by magneto-optical Kerr effect

Near-field autocorrelation spectroscopy of disordered semiconductor quantum wells

Channeling effects in heavy-ion irradiated NiAl(100) single-crystals: a TEM assessment in cross-section geometry using weak-beam imaging

Microdeformation mechanisms in thin films of amorphous semi-aromatic polyamides

Sol-gel derived Pb(Sc0.5Nb0.5)O-3 thin films: Processing and dielctric properties

Density clamping and longitudinal spatial hole burning in a gain-clamped semiconductor optical amplifier

Surface characterization of metallic molecular organic thin films: tetrathiafulvalene tetracyanoquinodimethane

Efficient, narrow linewidth excitonic emission at room temperature from GaAs/AlGaAs V-groove quantum wire light-emitting diodes

Net coherent optical gain in strongly pumped semiconductor microcavities

Effect of dopants on the crystallization mechanism of PZT thin films

Phase-transition-induced twinning in the 1 : 1 adduct of hexamethylenetetramine and azelaic acid

Modelling and simulation of a high accuracy magnetometer