168 research outputs found
Photocarrier Drift Mobility Measurements and Electron Localization in Nanoporous Silicon
We report photocarrier time-of-flight measurements in diode structures made of highly porous crystalline silicon. The corresponding electron and hole drift mobilities are very small ð\u3c104 cm2=V sÞ compared to homogeneous crystalline silicon. The mobilities are dispersive (i.e., having a power-law decay with time or length-scale), but are only weakly temperature-dependent. The dispersion parameter lies in the range 0.55–0.65 for both electrons and holes. We conclude that the drift mobilities are limited by the nanoporous geometry, and not by disorder-induced localized states acting as traps. This conclusion is surprising in the context of luminescence models based on radiative recombination of localized excitons
Deposition of Erbium Containing Film in Porous Silicon from Ethanol Solution of Erbium Salt
Electrochemical treatment of porous silicon (PS) in ethanol solution of Er(NO3)3 was investigated to obtain material suitable for optoelectronic application. The voltammograms of n+-type and p-type PS vs. an Ag/AgCl reference electrode were examined and compared with these of a Pt electrode. The basic cathode reactions were marked out the voltammograms: (i) the formation and the adsorption of atomic hydrogen; (ii) the formation of molecular hydrogen; (iii) the electrolysis of water and ethanol. No zones relating to on electrochemical transitions of Er ions were revealed on the voltammograms. Nevertheless, with the cathode polarization, the formation of an Er-containing deposit was observed at the surface of the cathode. The IR and SIMS analysis were used to study the composition of the deposits. The scheme of the electrochemical and chemical reactions at the cathode is discussed
Direct bandgap optical transitions in Si nanocrystals
The effect of quantum confinement on the direct bandgap of spherical Si
nanocrystals has been modelled theoretically. We conclude that the energy of
the direct bandgap at the -point decreases with size reduction: quantum
confinement enhances radiative recombination across the direct bandgap and
introduces its "red" shift for smaller grains. We postulate to identify the
frequently reported efficient blue emission (F-band) from Si nanocrystals with
this zero-phonon recombination. In a dedicated experiment, we confirm the "red"
shift of the F-band, supporting the proposed identification
Charge transfer state emission dynamics in blue-emitting functionalized silicon nanocrystals
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