Chemistry and Charge Trapping at the Interface of Silver and Ultrathin Layers of Zinc Oxide

M Rahamim, H Cohen, E Edri

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Zinc oxide, a wide-band-gap semiconductor, shows intriguing optoelectronic properties when coupled with Ag. Specifically, an absorbance band in the visible range that is not apparent in the separated materials emerges when the interface is formed. Interestingly, photoexcitation of this "interface band"or band-to-band results in a counterintuitive photovoltaic response when a supra/sub-band-gap light is shone. To investigate the origin of this absorbance band and photovoltaic response, we studied in detail the energy-band alignment of ultrathin layers of ZnO (3-60 nm) with Ag. Our analysis indicated that an ‘electrostatic potential cliff' is formed within the first 1-2 nm of ZnO. In addition, oxygen vacancies, presumably generated by AgxO-Zn bonds, form mid-gap acceptor states within these first few nm. Both effects facilitate a valence band-to-defect state optical transition that is confined to the interface region. The second type of defects - hole-trap states associated with zinc hydroxide - are spread throughout the ZnO layer and dominate the supra-band-gap photovoltaic response. These findings have potential implications in emerging technologies such as photocatalytic Ag/ZnO heterostructures that will utilize the long-lived charges for chemical work or other optoelectronic applications.

Original languageEnglish
Pages (from-to)49423-49432
Number of pages10
JournalACS applied materials & interfaces
Volume13
Issue number41
Early online date9 Oct 2021
DOIs
StatePublished - 20 Oct 2021

Keywords

  • Ag-ZnO
  • atomic layer deposition
  • interface defect states
  • surface photovoltage
  • thin films

ASJC Scopus subject areas

  • General Materials Science

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