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The Elastic Continuum Limit of the Tight Binding Model
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作者 Weinan E Jianfeng LU 《Chinese Annals of Mathematics,Series B》 SCIE CSCD 2007年第6期665-676,共12页
The authors consider the simplest quantum mechanics model of solids, the tight binding model, and prove that in the continuum limit, the energy of tight binding model converges to that of the continuum elasticity mode... The authors consider the simplest quantum mechanics model of solids, the tight binding model, and prove that in the continuum limit, the energy of tight binding model converges to that of the continuum elasticity model obtained using Cauchy-Born rule. The technique in this paper is based mainly on spectral perturbation theory for large matrices. 展开更多
关键词 Continuum limit Elasticity theory Cauchy-Born rule tight binding model
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Surface brightens up Si quantum dots: direct bandgap-like size-tunable emission 被引量:1
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作者 Katerina Dohnalova Alexander N Poddubny +5 位作者 Alexei A Prokofiev Wieteke DAM de Boer Chinnaswamy P Umesh Jos MJ Paulusse Han Zuilhof Tom Gregorkiewicz 《Light(Science & Applications)》 SCIE EI CAS 2013年第1期242-247,共6页
Colloidal semiconductor quantum dots(QDs)constitute a perfect material for ink-jet printable large area displays,photovoltaics,light-emitting diode,bio-imaging luminescent markers and many other applications.For this ... Colloidal semiconductor quantum dots(QDs)constitute a perfect material for ink-jet printable large area displays,photovoltaics,light-emitting diode,bio-imaging luminescent markers and many other applications.For this purpose,efficient light emission/absorption and spectral tunability are necessary conditions.These are currently fulfilled by the direct bandgap materials.Si-QDs could offer the solution to major hurdles posed by these materials,namely,toxicity(e.g.,Cd-,Pb-or As-based QDs),scarcity(e.g.,QD with In,Se,Te)and/or instability.Here we show that by combining quantum confinement with dedicated surface engineering,the biggest drawback of Si—the indirect bandgap nature—can be overcome,and a‘direct bandgap’variety of Si-QDs is created.We demonstrate this transformation on chemically synthesized Si-QDs using state-of-the-art optical spectroscopy and theoretical modelling.The carbon surface termination gives rise to drastic modification in electron and hole wavefunctions and radiative transitions between the lowest excited states of electron and hole attain‘direct bandgap-like’(phonon-less)character.This results in efficient fast emission,tunable within the visible spectral range by QD size.These findings are fully justified within a tight-binding theoretical model.When the C surface termination is replaced by oxygen,the emission is converted into the well-known red luminescence,with microsecond decay and limited spectral tunability.In that way,the‘direct bandgap’Si-QDs convert into the‘traditional’indirect bandgap form,thoroughly investigated in the past. 展开更多
关键词 direct bandgap optical spectroscopy OPTOELECTRONICS organic capping silicon quantum dots tight binding model
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