Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Non-radiative and Relaxation Processes
Abstract This chapter deals with the importance of non-radiative processes which can severely limit the luminescence properties of nanocrystals. We give two detailed examples of such processes: multi-phonon capture at surface point defects and Auger recombination of electron—hole pairs. Both are known to play a central role not only for silicon but also III–V and II–VI semiconductor nanocrystals embedded in different types of matrices. As a typical example of surface point defect, we choose the dangling bond for silicon crystallites in a SiO2 matrix. The reason is that the properties of such defects at the planar Si—SiO2 interface are well-known. Extrapolation of these results shows that one dangling bond is enough to kill the luminescence of the crystallites. In the second part, we describe a calculation of a phonon assisted Auger recombination process. This turns out to be efficient, in the nanosecond to 10 picosecond range for small crystallites, which is shown to explain several experimental observations on nanostructures. Finally, we concentrate on hot carrier relaxation processes. We first discuss the predicted existence of a phonon bottleneck for small crystallites which is an intrinsic effect limiting their optical properties. We end up this section by reviewing different processes which can overcome this limitation, again based essentially on Auger processes or capture on point defects followed by re-emission.
Non-radiative and Relaxation Processes
Abstract This chapter deals with the importance of non-radiative processes which can severely limit the luminescence properties of nanocrystals. We give two detailed examples of such processes: multi-phonon capture at surface point defects and Auger recombination of electron—hole pairs. Both are known to play a central role not only for silicon but also III–V and II–VI semiconductor nanocrystals embedded in different types of matrices. As a typical example of surface point defect, we choose the dangling bond for silicon crystallites in a SiO2 matrix. The reason is that the properties of such defects at the planar Si—SiO2 interface are well-known. Extrapolation of these results shows that one dangling bond is enough to kill the luminescence of the crystallites. In the second part, we describe a calculation of a phonon assisted Auger recombination process. This turns out to be efficient, in the nanosecond to 10 picosecond range for small crystallites, which is shown to explain several experimental observations on nanostructures. Finally, we concentrate on hot carrier relaxation processes. We first discuss the predicted existence of a phonon bottleneck for small crystallites which is an intrinsic effect limiting their optical properties. We end up this section by reviewing different processes which can overcome this limitation, again based essentially on Auger processes or capture on point defects followed by re-emission.
Non-radiative and Relaxation Processes
Dr. Delerue, Christophe (Autor:in) / Dr. Lannoo, Michel (Autor:in)
01.01.2004
16 pages
Aufsatz/Kapitel (Buch)
Elektronische Ressource
Englisch
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