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The microluminescence surface scan technique ~MSST! is used to investigate the lateral transport of photocarriers in a thin InGaAs-InP quantum well, under high optical excitation intensity ~0.3 to 30 KW/cm) and in the temperature range from 7 to 200 K. The size of the in-plane photocarrier distribution depends on both optical excitation intensity and temperature. A phonon-wind-driven mechanism is used to explain the behavior of the distribution at temperatures below 15 K. Further, the attenuation of the phonon flux during the photocarrier cloud expansion plays a key role in the phonon-wind mechanism. Finally, it is found that the phonon wind becomes quenched at high optical excitation intensity, which is probably correlated to an increasing carrier velocity greater than the sound velocity.

We study excitons bound to quantum wires of ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As embedded in an InP matrix, where the wires vary from 2.93 to 11.72 \AA{} (one to four monolayers) thick and from 25 to 250 \AA{} wide. We combine spectroscopic data from measurements of photoluminescence with variational calculations of the binding energies of excitons to the wires to deduce the wire widths and thicknesses. The widths are then related to the growth times to deduce lateral growth velocities in the vapor-levitation-epitaxial technique. Monolayer growth rates, at \ensuremath{\sim}80 \AA{}/sec, are significantly faster than growth rates for the multilayer wires.

We investigate a magnetic fluid composed of magnetite nanoparticles surfacted with dodecanoic acid molecules and stably dispersed in a hydrocarbon solvent. A comparison between Monte Carlo simulation and different experimental techniques allows us to validate our methodology and investigate the behavior of the surfactant molecules. Our analysis, based on the Langmuir model, suggests that the surfactant grafting number on isolate nanoparticles increases with the nanoparticle concentration, while the grafting on agglomerated nanoparticles presents a more complicated behavior. Our results suggests that, if properly coated and at a certain concentration range, colloids can become stable even in the presence of agglomerates. The role of the Hamaker constant, which controls the van der Waals interaction intensity, was also investigated. We have found that the ratio between grafting and Hamaker constant governs the level of nanoparticle agglomeration.

We have studied the energy-transfer process in InAs self-assembled quantum dots (QD’s) for low and high QD density, analyzing the spectral, spot size and excitation intensity dependence of the spatially resolved low-temperature cw microluminescence. We have observed energy transfer from small QD’s to larger QD’s even outside the excitation region over the sample. An amplified spontaneous emission driven energy-transfer mechanism is used to explain our results.