Spectroscopy and control of near-surface defects in conductive thin film ZnO

Leah L. Kelly, David A. Racke, Philip Schulz, Hong Li, Paul Winget, Hyungchul Kim, Paul Ndione, Ajaya K. Sigdel, Jean Luc Brédas, Joseph J. Berry, Samuel Graham, Oliver L A Monti Masel

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

The electronic structure of inorganic semiconductor interfaces functionalized with extended π-conjugated organic molecules can be strongly influenced by localized gap states or point defects, often present at low concentrations and hard to identify spectroscopically. At the same time, in transparent conductive oxides such as ZnO, the presence of these gap states conveys the desirable high conductivity necessary for function as electron-selective interlayer or electron collection electrode in organic optoelectronic devices. Here, we report on the direct spectroscopic detection of a donor state within the band gap of highly conductive zinc oxide by two-photon photoemission spectroscopy. We show that adsorption of the prototypical organic acceptor C60 quenches this state by ground-state charge transfer, with immediate consequences on the interfacial energy level alignment. Comparison with computational results suggests the identity of the gap state as a near-surface-confined oxygen vacancy.

Original languageEnglish (US)
Article number094007
JournalJournal of Physics Condensed Matter
Volume28
Issue number9
DOIs
StatePublished - Feb 12 2016

Fingerprint

Conductive films
Surface defects
surface defects
Spectroscopy
Zinc Oxide
Thin films
Electrons
Point defects
Oxygen vacancies
Photoelectron spectroscopy
thin films
Zinc oxide
Interfacial energy
Optoelectronic devices
Oxides
Electron energy levels
Ground state
spectroscopy
Electronic structure
Charge transfer

Keywords

  • gap state
  • hybrid organic/inorganic interface
  • two-photon photoemission
  • ZnO

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Materials Science(all)

Cite this

Spectroscopy and control of near-surface defects in conductive thin film ZnO. / Kelly, Leah L.; Racke, David A.; Schulz, Philip; Li, Hong; Winget, Paul; Kim, Hyungchul; Ndione, Paul; Sigdel, Ajaya K.; Brédas, Jean Luc; Berry, Joseph J.; Graham, Samuel; Monti Masel, Oliver L A.

In: Journal of Physics Condensed Matter, Vol. 28, No. 9, 094007, 12.02.2016.

Research output: Contribution to journalArticle

Kelly, LL, Racke, DA, Schulz, P, Li, H, Winget, P, Kim, H, Ndione, P, Sigdel, AK, Brédas, JL, Berry, JJ, Graham, S & Monti Masel, OLA 2016, 'Spectroscopy and control of near-surface defects in conductive thin film ZnO', Journal of Physics Condensed Matter, vol. 28, no. 9, 094007. https://doi.org/10.1088/0953-8984/28/9/094007
Kelly, Leah L. ; Racke, David A. ; Schulz, Philip ; Li, Hong ; Winget, Paul ; Kim, Hyungchul ; Ndione, Paul ; Sigdel, Ajaya K. ; Brédas, Jean Luc ; Berry, Joseph J. ; Graham, Samuel ; Monti Masel, Oliver L A. / Spectroscopy and control of near-surface defects in conductive thin film ZnO. In: Journal of Physics Condensed Matter. 2016 ; Vol. 28, No. 9.
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