Silicon Nanocrystallites in SiO2 Matrix: The Role of Disorder and Size

Abstract

We compare, through first-principles pseudopotential calculations, the structural, electronic and optical properties of different size silicon nanoclusters embedded in a SiO2 crystalline or amorphous matrix, with that of free-standing, hydrogenated and hydroxided silicon nanoclusters of corresponding size and shape. We find that the largest effect on the opto-electronic behavior is due to the amorphization of the embedded nanocluster. In that, the amorphization reduces the fundamental gap while increasing the absorption strength in the visible range. Increasing the nanocluster size does not change substantially this picture but only leads to the reduction of the absorption threshold, following the quantum confinement rule. Finally, through the calculation of the optical absorption spectra both in a indipendent-particle and many-body approach, we show that the effect of local fields is crucial for describing properly the optical behavior of the crystalline case while it is of minor importance for amorphous systems.

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• Local-field effects in silicon nanoclusters
• Energetics and carrier transport in doped Si/SiO2 quantum dots
• Role of strain in interacting silicon nanoclusters
• Local-fields and disorder effects in free-standing and embedded Si nanocrystallites
• Stark effect, polarizability and electroabsorption in silicon nanocrystals
• Electron correlations and silicon nanocluster energetics
• Carrier Multiplication in Silicon Nanocrystals: Theoretical Methodologies and Role of the Passivation
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