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Polarity-dependent photoemission of in situ cleaved zinc oxide single crystals

Published online by Cambridge University Press:  30 July 2012

Robert Heinhold  and
Martin Ward Allen
Robert Heinhold*
Affiliation:
Department of Electrical and Computer Engineering, University of Canterbury, Christchurch 8140, New Zealand; and The MacDiarmid Institute for Advanced Materials and Nanotechnology, Christchurch 8140, New Zealand
Martin Ward Allen*
Affiliation:
Department of Electrical and Computer Engineering, University of Canterbury, Christchurch 8140, New Zealand; and The MacDiarmid Institute for Advanced Materials and Nanotechnology, Christchurch 8140, New Zealand
*
a)Address all correspondence to these authors. e-mail: [email protected]
b)e-mail: [email protected]
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Abstract

X-ray photoemission spectroscopy using synchrotron radiation from 100 to 1486.6 eV was used to investigate polarity-dependent differences between the Zn-polar (0001) and the O-polar () faces of ultrahigh vacuum cleaved hydrothermally grown ZnO single crystals. The cleaved polar surfaces showed a characteristic polarity effect in that the intensity of emission from the lowest binding energy O 2p related valence band states was significantly stronger on the Zn-polar face, even when the cleaved surfaces were imperfect with irregular nonatomically flat features. A residual submonolayer hydroxyl termination of approximately 0.5 ML was observed on both the Zn-polar and O-polar surfaces immediately after cleaving. The near-surface downward band bending on the O-polar face was removed by the cleaving process leaving almost flat bands, while on the cleaved Zn-polar face, emission from states above the valence band edge was observed.

Keywords

ZnOx-ray photoelectron spectroscopypolarityhydroxyl coverageZn-polarO-polar
Type
Articles
Information
Journal of Materials Research , Volume 27 , Issue 17: Focus Issue: Oxide Semiconductors , 14 September 2012 , pp. 2214 - 2219
Copyright
Copyright © Materials Research Society 2012

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