Size, oxidation, and strain in small Si/SiO2 nanocrystals

Abstract

The structural, electronic and optical properties of Si nanocrystals of different size and shape, passivated with hydrogens, OH groups, or embedded in a SiO2 matrix are studied. The comparison between the embedded and free, suspended nanocrystals shows that the silica matrix produces a strain on the embedded NCs, that contributes to determine the band gap value. By including the strain on the hydroxided nanocrystals we are able to reproduce the electronic and optical properties of the full Si/SiO2 systems. Moreover we found that, while the quantum confinement dominates in the hydrogenated nanocrystals of all sizes, the behaviour of hydroxided and embedded nanocrystals strongly depends on the interface oxidation degree, in particular for diameters below 2 nm. Here, the proportion of NC atoms at the Si/SiO2 interface becomes relevant, producing surface-related states that may affect the quantum confinement appearing as inner band gap states and then drastically changing the optical response of the system.

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Cited by in corpus (10)

• Theoretical analysis of electronic band structure of 2-to-3-nm Si nanocrystals
• Preferential positioning of dopants and co-dopants in embedded and freestanding Si nanocrystals
• High Luminescence in Small Si/SiO2 Nanocrystals: A Theoretical Study
• Doped and Codoped Silicon Nanocrystals: the Role of Surfaces and Interfaces
• Optical absorption and emission of silicon nanocrystals: From single to collective response
• Local-field effects in silicon nanoclusters
• Energetics and carrier transport in doped Si/SiO2 quantum dots
• Role of strain in interacting silicon nanoclusters
• Electronic Structure Shift of Deep Nanoscale Silicon by SiO${}_2$- vs. Si${}_3$N${}_4$-Embedding as Alternative to Impurity Doping
• Excitation transport in quantum devices: analytical time-dependent non-equilibrium green function algorithm