The case study of a 32-atoms Si nanocrystallite (NC) embeddedin a SiO2 matrix, both crystalline and amorphous, or freestandingwith different conditions of passivation and strain isanalyzed through ab-initio approaches. The Si32/SiO2 heterojunctionshows a type I band offset highlighting a separationbetween the NC plus the interface and the matrix around. Theconsequence of this separation is the possibility to correctlyreproduce the low energy electronic and optical properties ofthe composed system simply by studying the suspended NCplus interface oxygens with the appropriate strain. Moreover,through the definition of an optical absorption threshold wefound that, beside the quantum confinement trend, theamorphization introduces an additional redshift that increaseswith increasing NC size, i.e. the gap tends faster to the bulklimit. Finally, the important changes in the calculated DFTRPAoptical spectra upon inclusion of local fields point towardsthe need of a proper treatment of the optical response of theinterface region.

Local-fields and disorder effects in free-standing and embedded Si nanocrystallites / Guerra, Roberto; Degoli, Elena; M., Marsili; O., Pulci; Ossicini, Stefano. - In: PHYSICA STATUS SOLIDI B-BASIC RESEARCH. - ISSN 0370-1972. - STAMPA. - 247:(2010), pp. 2113-2117. [10.1002/pssb.200983926]

Local-fields and disorder effects in free-standing and embedded Si nanocrystallites

GUERRA, Roberto;DEGOLI, Elena;OSSICINI, Stefano
2010

Abstract

The case study of a 32-atoms Si nanocrystallite (NC) embeddedin a SiO2 matrix, both crystalline and amorphous, or freestandingwith different conditions of passivation and strain isanalyzed through ab-initio approaches. The Si32/SiO2 heterojunctionshows a type I band offset highlighting a separationbetween the NC plus the interface and the matrix around. Theconsequence of this separation is the possibility to correctlyreproduce the low energy electronic and optical properties ofthe composed system simply by studying the suspended NCplus interface oxygens with the appropriate strain. Moreover,through the definition of an optical absorption threshold wefound that, beside the quantum confinement trend, theamorphization introduces an additional redshift that increaseswith increasing NC size, i.e. the gap tends faster to the bulklimit. Finally, the important changes in the calculated DFTRPAoptical spectra upon inclusion of local fields point towardsthe need of a proper treatment of the optical response of theinterface region.
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2113
2117
Local-fields and disorder effects in free-standing and embedded Si nanocrystallites / Guerra, Roberto; Degoli, Elena; M., Marsili; O., Pulci; Ossicini, Stefano. - In: PHYSICA STATUS SOLIDI B-BASIC RESEARCH. - ISSN 0370-1972. - STAMPA. - 247:(2010), pp. 2113-2117. [10.1002/pssb.200983926]
Guerra, Roberto; Degoli, Elena; M., Marsili; O., Pulci; Ossicini, Stefano
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11380/636118
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