Carrier dynamics within semiconductor nanocrystals

This thesis explores how the carrier dynamics within semiconductor nanocrystals can be directly engineered through specific core-shell design. Emphasis is placed on how material characteristics, such as strain or alloying at a core-shell interface, can influence the exciton energies and the recombin...

Full description

Saved in:
Bibliographic Details
Main Author Fairclough, Simon Michael
Format Dissertation
LanguageEnglish
Published University of Oxford 2012
Subjects
Online AccessGet full text

Cover

Loading…
Abstract This thesis explores how the carrier dynamics within semiconductor nanocrystals can be directly engineered through specific core-shell design. Emphasis is placed on how material characteristics, such as strain or alloying at a core-shell interface, can influence the exciton energies and the recombination dynamics within semiconductor nanocrystals. This study synthesises type-II heterojunction ZnTe/ZnSe core-shell nanocrystals via a diethyl zinc-free synthesis method, producing small size distributions and quantum yields as high as 12%. It was found that the 7% lattice mismatch between the core and shell materials places limitations on the range of structures in which coherent growth is achieved. By developing compositional and strained atomistic core-shell models a variety of physical and optical properties could be simulated and has led to a clear picture of the core-shell architecture to be built. This characterisation provides evidence that the low bulk modulus ZnTe cores are compressed by the higher bulk modulus smaller lattice constant ZnSe shells. Further studies show how strain is manifested in structures with 'sharp' core-shell interfaces and how intentional alloying the interface can influence the growth and exciton energies. A (2-6)-band effective mass model was able to distinguish between the as-grown 'sharp' and 'alloyed' interfaces which indicated that strain accentuates the redshift of the excitonic state whilst reduced strain within an alloyed interface sees a reduced redshift. Single nanocrystal spectroscopy investigations of brightly emitting single graded alloyed nanocrystals and of a size series of commercially available CdSe/ZnS nanocrystals showed almost no fluorescence intermittency (nearly 'non-blinking'). These investigations also identified trion recombination as the main mechanism within the blinking 'off' state. Ultimately this thesis adds to the growing understanding of how specific core-shell architectures manipulate the electronic structure and develops techniques to identify specific material characteristics and how these characteristics influence the physical and optical properties within semiconductor nanocrystals.
AbstractList This thesis explores how the carrier dynamics within semiconductor nanocrystals can be directly engineered through specific core-shell design. Emphasis is placed on how material characteristics, such as strain or alloying at a core-shell interface, can influence the exciton energies and the recombination dynamics within semiconductor nanocrystals. This study synthesises type-II heterojunction ZnTe/ZnSe core-shell nanocrystals via a diethyl zinc-free synthesis method, producing small size distributions and quantum yields as high as 12%. It was found that the 7% lattice mismatch between the core and shell materials places limitations on the range of structures in which coherent growth is achieved. By developing compositional and strained atomistic core-shell models a variety of physical and optical properties could be simulated and has led to a clear picture of the core-shell architecture to be built. This characterisation provides evidence that the low bulk modulus ZnTe cores are compressed by the higher bulk modulus smaller lattice constant ZnSe shells. Further studies show how strain is manifested in structures with 'sharp' core-shell interfaces and how intentional alloying the interface can influence the growth and exciton energies. A (2-6)-band effective mass model was able to distinguish between the as-grown 'sharp' and 'alloyed' interfaces which indicated that strain accentuates the redshift of the excitonic state whilst reduced strain within an alloyed interface sees a reduced redshift. Single nanocrystal spectroscopy investigations of brightly emitting single graded alloyed nanocrystals and of a size series of commercially available CdSe/ZnS nanocrystals showed almost no fluorescence intermittency (nearly 'non-blinking'). These investigations also identified trion recombination as the main mechanism within the blinking 'off' state. Ultimately this thesis adds to the growing understanding of how specific core-shell architectures manipulate the electronic structure and develops techniques to identify specific material characteristics and how these characteristics influence the physical and optical properties within semiconductor nanocrystals.
Author Fairclough, Simon Michael
Author_xml – sequence: 1
  fullname: Fairclough, Simon Michael
BookMark eNotjMkKwjAURbPQhdM_9AcKGZo0LqU4geBG1-VlKA3WBJIU6d9b0NW55y7OGi188HaFaAMxOhsLM3l4O52Kj8u980WyswVvRp1DLDz4oOOUMgxpi5bdDLv7c4Oep-OjuZS3-_naHG6lIpjz0lS0xpLWsrN4z2THjBGqo9gCJ4pxXQmoiKgwgFFScDLfzAqGjayFIFqzDaK_roouu9QPTkWIU2tzH1IbwP2XGtrx1XJJiOTsC7MMQ10
ContentType Dissertation
DBID ABQQS
LLH
DEWEY 620.115
DatabaseName EThOS: Electronic Theses Online Service (Full Text)
EThOS: Electronic Theses Online Service
DatabaseTitleList
Database_xml – sequence: 1
  dbid: LLH
  name: EThOS: Electronic Theses Online Service
  url: http://ethos.bl.uk/
  sourceTypes: Open Access Repository
DeliveryMethod fulltext_linktorsrc
Discipline Engineering
DissertationAdvisor Smith, Jason M
DissertationAdvisor_xml – sequence: 1
  fullname: Smith, Jason M
DissertationDegree Thesis (Ph.D.)
DissertationSchool University of Oxford
ExternalDocumentID oai_ethos_bl_uk_581185
GroupedDBID ABQQS
LLH
ID FETCH-LOGICAL-b1055-d42708278fe0938f3dd6bf20ea51b35c46a41640aadb8651a513e630d87661cc3
IEDL.DBID LLH
IngestDate Tue Apr 04 21:56:16 EDT 2023
IsOpenAccess true
IsPeerReviewed false
IsScholarly false
Language English
LinkModel DirectLink
MergedId FETCHMERGED-LOGICAL-b1055-d42708278fe0938f3dd6bf20ea51b35c46a41640aadb8651a513e630d87661cc3
Notes EPRSC
0000000427460373
OpenAccessLink http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.581185
ParticipantIDs britishlibrary_ethos_oai_ethos_bl_uk_581185
PublicationCentury 2000
PublicationDate 2012
PublicationDateYYYYMMDD 2012-01-01
PublicationDate_xml – year: 2012
  text: 2012
PublicationDecade 2010
PublicationYear 2012
Publisher University of Oxford
Publisher_xml – name: University of Oxford
Score 1.6239291
Snippet This thesis explores how the carrier dynamics within semiconductor nanocrystals can be directly engineered through specific core-shell design. Emphasis is...
SourceID britishlibrary
SourceType Open Access Repository
SubjectTerms alloy
blinking
core-shell nanoparticles
nanocrystals
Nanomaterials
nanoparticle
Nanostructures
quantum dots
semiconductor nanocrystals
strain
type-II heterojunction
Title Carrier dynamics within semiconductor nanocrystals
URI http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.581185
hasFullText 1
inHoldings 1
isFullTextHit
isPrint
link http://utb.summon.serialssolutions.com/2.0.0/link/0/eLvHCXMwlV3LSgMxFL1o3VgRfOKbWbiTlEkmyaQLcdFailTdWOhuyBNLSwbmsfDvTTpd1KW7kFwCuZtzcnNzDsCjHFojcmsQd1YiqrFCgmcUEWwczi12jMbPye8ffDqnbwu22Fp9xZpu813WA7WOv6g-o_bkeNNIWQ9M-dIu_XO7iotdFBOBHLN9OCCBk0Tzgtls2odj1YkBbYsgO2AxOYGj8c4j9ynsWX8G_R3hv3MgI1lFq7jEdIbwdRLroUuf1LFXvfRRhLWsEi99qaufQODW9QXMJ69foynauhcgFU0nkaEkD_iaC2fTYSZcZgxXjqRWMqwypimXgQzRVEqjBGc4TGeWZ2lIXcBMrbNL6PnS2ytIdM7DVkYzzB0dOiLDLUNZoaQM9Edhfg1Pf09dbDJUROnobqTWRbsquozd_Cv6Fg4DRyBd1eEOek3V2vuAw4162GT8F6v2khg
link.rule.ids 230,311,780,885,4052,26562
linkProvider British Library Board
openUrl ctx_ver=Z39.88-2004&ctx_enc=info%3Aofi%2Fenc%3AUTF-8&rfr_id=info%3Asid%2Fsummon.serialssolutions.com&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adissertation&rft.genre=dissertation&rft.title=Carrier+dynamics+within+semiconductor+nanocrystals&rft.DBID=ABQQS%3BLLH&rft.au=Fairclough%2C+Simon+Michael&rft.date=2012&rft.pub=University+of+Oxford&rft.advisor=Smith%2C+Jason+M&rft.inst=University+of+Oxford&rft.externalDBID=n%2Fa&rft.externalDocID=oai_ethos_bl_uk_581185