Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Radiative emission from multiphoton-excited semiconductor quantum dots
KTH, School of Biotechnology (BIO), Theoretical Chemistry.
KTH, School of Biotechnology (BIO), Theoretical Chemistry.ORCID iD: 0000-0002-2442-1809
KTH, School of Biotechnology (BIO), Theoretical Chemistry.ORCID iD: 0000-0002-1763-9383
2007 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 6, 063712-1-063712-6 p.Article in journal (Refereed) Published
Abstract [en]

Optical transitions in CdS semiconductor quantum dots (QDs) have been studied by the Monte Carlo method based on probability calculations of the time-dependent Schrodinger equation. It has been demonstrated that excited by a continuous-wave laser, an assembly of CdS QDs, whose radii range from 2 to 5 nm centered at 3.7 nm, shows an emission peak around 2.65 eV in the optical emission spectrum, which corresponds to optical transitions among degenerate sublevels close to the ground sublevels in the conduction and valence bands of a CdS QD having a radius of 3.7 nm. For resonant one-photon excitation, the emission peak is very sharp, while for resonant two-photon excitation, the emission peak becomes blueshifted and broadened. The inclusion of the nonradiative electron-phonon processes makes the two-photon excitation peak significantly sharper and shows a better agreement with experimental work, thus demonstrating the upconversion luminescence of the QDs required for many applications including bioimaging.

Place, publisher, year, edition, pages
2007. Vol. 101, no 6, 063712-1-063712-6 p.
Keyword [en]
Continuous wave lasers; Monte Carlo methods; Photons; Radiative transfer; Schrodinger equation; Valence bands; Emission peaks; Ground sublevels; Probability calculations; Two photon excitation
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-8232DOI: 10.1063/1.2715811ISI: 000245317700083Scopus ID: 2-s2.0-34047130675OAI: oai:DiVA.org:kth-8232DiVA: diva2:13497
Note
QC 20100730Available from: 2008-04-18 Created: 2008-04-18 Last updated: 2010-07-30Bibliographically approved
In thesis
1. Optical Properties of Low Dimensional Semiconductor Materials
Open this publication in new window or tab >>Optical Properties of Low Dimensional Semiconductor Materials
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This dissertation presents a serial study on optical properties of different semiconductor materials. Three main types of studies are addressed: The role of doping levels of N and Al atoms in the room-temperature photoluminescence (PL) of 4H-SiC films for optoelectronic applications; the use of a basic Monte Carlo method combined with probability calculations of the time-dependent Schroedinger equation to manifest multi-photon absorption and emission of II-VI compound quantum dots (QDs) for bioimaging; a theoretical quantum chemistry approach to study of structure and optical properties of InGaAsN and GaAs clusters for laser technology applications. 4H-SiC films were grown on AlN/SiC(100) substrates by a chemical vapour deposition (CVD) system. Three well-defined room-temperature PL peaks close to the band-gap energy were observed. By a detailed theoretical analysis of optical transitions in the samples, it was found that the PL peaks are most probably due to the optical transitions between impurity levels and band edges, and the transition between the second minimum of the conduction band and the top of the valance band. Special attention has been paid to effects of doping levels of N and Al impurities. Optical transitions in several II-VI semiconductor QDs have been studied by a quantum Monte Carlo method. We model the QD energy band structure by a spherical square quantum well and the electrons in the conduction band and holes in the valence band by the effective mass approximation. The optical probabilities of optical transitions induced by ultrafast and ultraintense laser pulses are calculated from the time-dependent Schroedinger equation. With the inclusion of the nonradiative electron-phonon processes, the calculated absorption and emission spectra are in agreement with experimental work. The dynamic processes and up-conversion luminescence of the QDs, required for many applications including bio-imaging, are demonstrated. Quantum chemistry is used to study InGaAsN and GaAs nano systems. The molecular structures of a series of dilute-nitride zinc blende InGaNAs clusters are examined from the energy point of view with a semi-empirical method. The optimum cluster configurations are identified by which we can identify the detailed bonding structures and the effects of In mole fraction. After proper geometry construction, an effective central insertion scheme has been implemented to study the electronic band structures of GaAs at the first-principles level. The formation of energy bands and quantum confinement effects have been revealed, thus providing theoretical support for laser design.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. 58 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2008:8
Keyword
Semiconductor, Low dimensional, optics
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-4699 (URN)978-91-7178-909-9 (ISBN)
Public defence
2008-04-29, FA31, Roslagstullsbacken 21, AlbaNova, Stockholm, 14:00
Opponent
Supervisors
Note
QC 20100730Available from: 2008-04-18 Created: 2008-04-18 Last updated: 2010-07-30Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Authority records BETA

Fu, YingÅgren, Hans

Search in DiVA

By author/editor
Han, TiantianFu, YingÅgren, Hans
By organisation
Theoretical Chemistry
In the same journal
Journal of Applied Physics
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 41 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf