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Defects in Irradiated ZnO Thin Films Studied by Photoluminescence and Photoconductivity

Published online by Cambridge University Press:  01 February 2011

Reinhard Schwarz ,
Rachid Ayouchi ,
Marta Brandão ,
Carlos Marques ,
Eduardo Alves ,
Melanie Pinnisch ,
Detlev Hofmann  and
Bruno Meyer
Reinhard Schwarz
Affiliation:
rschwarz@fisica.ist.utl.pt, Instituto Superior Tecnico, Departamento de Fisica, Lisbon, Portugal
Rachid Ayouchi
Affiliation:
rachid.ayouchi@ist.utl.pt, Instituto Superior Tecnico, Departamento de Fisica, Lisbon, Portugal
Marta Brandão
Affiliation:
martamrbrandao@gmail.com, Instituto Superior Tecnico, Departamento de Fisica, Lisbon, Portugal
Carlos Marques
Affiliation:
cmarques@itn.mctes.pt, Instituto Tecnologico e Nuclear, Sacavem, Portugal
Eduardo Alves
Affiliation:
ealves@itn.mctes.pt, Instituto Tecnologico e Nuclear, Sacavem, Portugal
Melanie Pinnisch
Affiliation:
Melanie.Pinnisch@physik.uni-giessen.de, University of Giessen, Institut of Applied Physics I, Giessen, Germany
Detlev Hofmann
Affiliation:
detlev.m.hofmann@exp1.physik.uni-giessen.de, University of Giessen, Institut of Applied Physics I, Giessen, Germany
Bruno Meyer
Affiliation:
Bruno.K.Meyer@exp1.physik.uni-giessen.de, University of Giessen, Institut of Applied Physics I, Giessen, Germany
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Abstract

Pulsed-laser-deposited ZnO thin films were exposed to a 1.5 MeV helium ion beam to study the changes in radiative and non-radiative recombination. We first measured photoluminescence (PL) spectra at 4.2 K excited with the 325 nm line of a HeCd laser. The as-deposited films showed a donor-bound exciton peak at 3.3567 eV attributed to Zn interstitials. After irradiation the donor-bound-exciton dominated PL spectra shifted to acceptor-bound behaviour with a signal at 3.3519 eV, tentatively attributed to Li or Na acceptors. In contrast to the approximately 30 % decrease of the PL signal near the band edge, we observed a strong concomitant enhancement of the green/orange PL band, located between 2.1 eV and 2.8 eV, by a factor of over 4. Candidates for those transitions are Li impurities and/or O vacancies. For comparison, the steady-state photocurrent decreased strongly in the irradiated region, which can also be attributed to increased non-radiative recombination through oxygen-related defects.

Keywords

defectslaser ablationoptoelectronic
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1268: Symposium EE – Defects in Inorganic Photovoltaic Materials , 2010 , 1268-EE01-05
Copyright
Copyright © Materials Research Society 2010

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