Effect of controlled oxidation processes on the emission and excitation of porous silicon
Rigakis, Nikolaos
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https://hdl.handle.net/2142/30766
Description
Title
Effect of controlled oxidation processes on the emission and excitation of porous silicon
Author(s)
Rigakis, Nikolaos
Issue Date
1997
Director of Research (if dissertation) or Advisor (if thesis)
Nayfeh, Munir H.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
quantum confinement
quantum efficiency
porous silicon
crystalline silicon
luminescence
Language
en
Abstract
The strong luminescence activity of porous silicon prepared by anodization of
silicon in HF is a remarkable phenomenon, considering the fact that ordinary crystalline silicon is not at all an efficient light emitter due to the indirect character of its bandgap. In spite of the intense theoretical and experimental activity, the basic mechanism responsible for this efficient luminescence is still under debate. Nevertheless, there is a growing consensus that quantum confinement in nanocrystallites is an important element of this mechanism. However, there are two competing models, both based on quantum confinement, namely bulk-like radiative recombination and novel radiative surface state recombination. In small crystallites the number of surface atoms is a sizeable fraction of the total and therefore surface conditions (both type and quality) are expected to play an important role. We have performed time-resolved emission in the JLSec regime and excitation measurements of porous silicon and studied the quantum efficiency under various surface oxidation
treatments. We have found that, although the overall quantum efficiency (and hence the brightness of the porous surface) can vary a lot as a function of surface conditions, the time behavior of the luminescence is only weakly affected by these conditions. This leads to the conclusion that the emitting states are pretty much unaffected by the various surface treatments and consequently we believe that most likely one or both of the radiatively recombining carriers are localized.
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