Silicon nanocrystals (NCs) represent one of the most promising material systems for light emission applications in microphotonics. In recent years, several groups have reported on the observation of optical gain or stimulated emission in silicon NCs or in porous silicon (PSi). These results suggest that silicon-NC-based waveguide amplifiers or silicon lasers are achievable. However, in order to obtain clear and reproducible evidence of stimulated emission, it is necessary to understand the physical mechanisms at work in the light emission process. In this paper, we report on the detailed theoretical aspects of the energy levels and recombination rates in doped and undoped Si NCs, and we discuss the effects of energy transfer mechanisms. The theoretical calculations are extended toward computational simulations of ensembles of interacting nanocrystals. We will show that inhomogeneous broadening and energy transfer remain significant problems that must be overcome in order to improve the gain profile and to minimize nonradiative effects. Finally, we suggest means by which these objectives may be achieved.

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Abstract— Chemiluminescence in the visible region during liquid‐phase hydrocarbon oxidation is excited by peroxy radical disproportionation; a carbonyl compound, P, in the triplet state is the emitter. Several types of energy transfer from P to acceptors are considered. These provide valuable information (lifetimes, rate constants, emission yields) relevant to triplet state molecules. The excitation yields are estimated making use of this information, the absolute chemiluminescence intensities and the reaction rates. Electronic excitation of P, vibrational excitation of ground state P and reverse decomposition of an intermediate complex into initial peroxy radicals are considered as competing processes strongly dependent on transformation of chemical energy into vibrations.

The valley-orbit splitting in silicon quantum dots with shallow donors has been theoretically studied. In particular, the chemical-shift calculation was carried out within the frames of k · p approximation for singleand many-donor cases. For both cases, the great value of the chemical shift has been obtained compared to its bulk value. Such increase of the chemical shift becomes possible due to the quantum confinement effect in a dot. It is shown for the single-donor case that the level splitting and chemical shift strongly depend on the dot radius and donor position inside the nanocrystal. In the many-donor case, the chemical shift is almost proportional to the number of donors.

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