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Photoluminescence of compact GeSi quantum dot groups with increased probability of finding an electron in Ge.

ABSTRACT: The photoluminescence (PL) of the combined Ge/Si structures representing a combination of large (200-250?nm) GeSi disk-like quantum dots (nanodisks) and four-layered stacks of compact groups of smaller (30?nm) quantum dots grown in the strain field of nanodisks was studied. The multiple increase in the PL intensity was achieved by the variation of parameters of vertically aligned quantum dot groups. The experimental results were analyzed on the basis of calculations of energy spectra, electron and hole wave functions. It was found that the quantum dot arrangement in compact groups provides the effective electron localization in ?_x,y-valleys with an almost equal probability of finding an electron in the Si spacer and Ge barrier. As a result, the main channels of radiative recombination in the structures under study correspond to spatially direct optical transitions.

SUBMITTER: Zinovieva AF

PROVIDER: S-EPMC7283240 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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Photoluminescence of compact GeSi quantum dot groups with increased probability of finding an electron in Ge.

Zinovieva A F AF Zinovyev V A VA Nenashev A V AV Teys S A SA Dvurechenskii A V AV Borodavchenko O M OM Zhivulko V D VD Mudryi A V AV

Scientific reports 20200609 1

The photoluminescence (PL) of the combined Ge/Si structures representing a combination of large (200-250 nm) GeSi disk-like quantum dots (nanodisks) and four-layered stacks of compact groups of smaller (30 nm) quantum dots grown in the strain field of nanodisks was studied. The multiple increase in the PL intensity was achieved by the variation of parameters of vertically aligned quantum dot groups. The experimental results were analyzed on the basis of calculations of energy spectra, electron a ...[more]

PMID: 32518243

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Project description:Charge transfer processes with semiconductor quantum dots (QDs) have generated much interest for potential utility in energy conversion. Such configurations are generally nonbiological; however, recent studies have shown that a redox-active ruthenium(II)-phenanthroline complex (Ru2+-phen) is particularly efficient at quenching the photoluminescence (PL) of QDs, and this mechanism demonstrates good potential for application as a generalized biosensing detection modality since it is aqueous compatible. Multiple possibilities for charge transfer and/or energy transfer mechanisms exist within this type of assembly, and there is currently a limited understanding of the underlying photophysical processes in such biocomposite systems where nanomaterials are directly interfaced with biomolecules such as proteins. Here, we utilize redox reactions, steady-state absorption, PL spectroscopy, time-resolved PL spectroscopy, and femtosecond transient absorption spectroscopy (FSTA) to investigate PL quenching in biological assemblies of CdSe/ZnS QDs formed with peptide-linked Ru2+-phen. The results reveal that QD quenching requires the Ru2+ oxidation state and is not consistent with Förster resonance energy transfer, strongly supporting a charge transfer mechanism. Further, two colors of CdSe/ZnS core/shell QDs with similar macroscopic optical properties were found to have very different rates of charge transfer quenching, by Ru2+-phen with the key difference between them appearing to be the thickness of their ZnS outer shell. The effect of shell thickness was found to be larger than the effect of increasing distance between the QD and Ru2+-phen when using peptides of increasing persistence length. FSTA and time-resolved upconversion PL results further show that exciton quenching is a rather slow process consistent with other QD conjugate materials that undergo hole transfer. An improved understanding of the QD-Ru2+-phen system can allow for the design of more sophisticated charge-transfer-based biosensors using QD platforms.

Dataset Information

Photoluminescence of compact GeSi quantum dot groups with increased probability of finding an electron in Ge.

Publications

Photoluminescence of compact GeSi quantum dot groups with increased probability of finding an electron in Ge.

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