Photoinduced oxygen release and persistent photoconductivity in ZnO nanowires

Jiming Bao, Ilan Shalish, Zhihua Su, Ron Gurwitz, Federico Capasso, Xiaowei Wang, Zhifeng Ren

Research output: Contribution to journalArticlepeer-review

173 Scopus citations

Abstract

Photoconductivity is studied in individual ZnO nanowires. Under ultraviolet (UV) illumination, the induced photocurrents are observed to persist both in air and in vacuum. Their dependence on UV intensity in air is explained by means of photoinduced surface depletion depth decrease caused by oxygen desorption induced by photogenerated holes. The observed photoresponse is much greater in vacuum and proceeds beyond the air photoresponse at a much slower rate of increase. After reaching a maximum, it typically persists indefinitely, as long as good vacuum is maintained. Once vacuum is broken and air is let in, the photocurrent quickly decays down to the typical air-photoresponse values. The extra photoconductivity in vacuum is explained by desorption of adsorbed surface oxygen which is readily pumped out, followed by a further slower desorption of lattice oxygen, resulting in a Zn-rich surface of increased conductivity. The adsorption-desorption balance is fully recovered after the ZnO surface is exposed to air, which suggests that under UV illumination, the ZnO surface is actively "breathing" oxygen, a process that is further enhanced in nanowires by their high surface to volume ratio.

Original languageEnglish
Article number404
Pages (from-to)1-7
Number of pages7
JournalNanoscale Research Letters
Volume6
DOIs
StatePublished - 1 Dec 2011

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics

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