Calculation of the energy spectrum of nano-meter-sized silicon

Vladimir Gavrilenko, Peter Vogl, Frederick Koch

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

10 Scopus citations

Abstract

A large number of experiments on porous silicon has reliably demonstrated that the onset of optical absorption is shifted to energies significantly above the band edge of bulk Si. This increased transparency of the small nanometer-sized crystallites with their H-covered surfaces is a fact that asks for theoretical interpretation. Handwaving arguments about quantum size effect can only be a qualitative guide. We present here a tight binding calculation of a Si slab with nanometer dimensions covered with hydrogen. This is a model system for one-dimensional confinement. We consider the effect on the electron energy structure, the total and local densities of states of Si covered with hydrogen in two phases: monohydride - Si: H (2×1) symmetric dimer, and dihydride phases - Si: H2 (1×1) A total energy minimization method in the framework of the self-consistent tight binding theory has been used to investigate the structural reconstruction of the Si-surface after the adsorption of hydrogen. We find, that the band gap of the slab covered with H on both sides (monohydride phase) shifts to higher energies (typically approximately 1.8 eV for 1.16 nm thick slab). The adsorption of hydrogen removes all the electronic states from the gap for both phases investigated. In nanometer sized slabs the lowest electronic states in the conduction band are localized on the surface Si-atoms, in contrast to thicker slabs. We discuss the implication of this model calculation to light emission in porous Si.

Original languageEnglish
Title of host publicationMaterials Research Society Symposium Proceedings
PublisherPubl by Materials Research Society
Pages431-436
Number of pages6
ISBN (Print)1558991786
StatePublished - 1993
EventProceedings of the Second Symposium on Dynamics in Small Confining Systems - Boston, MA, USA
Duration: 30 Nov 19924 Dec 1992

Publication series

NameMaterials Research Society Symposium Proceedings
Volume283
ISSN (Print)0272-9172

Conference

ConferenceProceedings of the Second Symposium on Dynamics in Small Confining Systems
CityBoston, MA, USA
Period30/11/924/12/92

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