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Surface brightens up Si quantum dots: direct bandgap-like size-tunable emission

Light(Science & Applications) 2013年第1期2卷 242-247页

作者： Katerina Dohnalova Alexander N Poddubny alexei a prokofiev Wieteke DAM de Boer Chinnaswamy P Umesh Jos MJ Paulusse Han Zuilhof Tom Gregorkiewicz Van der Waals-Zeeman Institute University of AmsterdamNL-1098 XH AmsterdamThe Netherlands Laboratory of Organic Chemistry Wageningen University6703 HB WageningenThe Netherlands Department of Chemical and Materials Engineering King Abdulaziz UniversityJeddahSaudi Arabia Ioffe Physical-Technical Institute RAS 26 Polytechnicheskaya194021 Saint-PetersburgRussia Current address:MIRA Institute Department of Biomedical ChemistryUniversity of TwenteBuilding Zuidhorst EnschedeThe Netherlands

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 *** this purpose,efficient light emission/absorption and spectral tunability are necessary *** are currently fulfilled by the direct bandgap ***-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 *** 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 *** demonstrate this transformation on chemically synthesized Si-QDs using state-of-the-art optical spectroscopy and theoretical *** 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)*** results in efficient fast emission,tunable within the visible spectral range by QD *** findings are fully justified within a tight-binding theoretical *** the C surface termination is replaced by oxygen,the emission is converted into the well-known red luminescence,with microsecond decay and limited spectral *** that way,the‘direct bandgap’Si-QDs convert into the‘traditional’indirect bandgap form,thoroughly investigated in the past.

关键词： direct bandgap optical spectroscopy optoelectronics organic capping silicon quantum dots tight binding model

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