Identification of substitutional Li in n-type ZnO and its role as an acceptor

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2011-06
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Mcode
Degree programme
Language
en
Pages
7
1-7
Series
PHYSICAL REVIEW B, Volume 83, issue 24
Abstract
Monocrystalline n-type zinc oxide (ZnO) samples prepared by different techniques and containing various amounts of lithium (Li) have been studied by positron annihilation spectroscopy (PAS) and secondary ion mass spectrometry. A distinct PAS signature of negatively charged Li atoms occupying a Zn-site (Li−Zn), so-called substitutional Li, is identified and thus enables a quantitative determination of the content of LiZn. In hydrothermally grown samples with a total Li concentration of ~2×1017cm−3,LiZn is found to prevail strongly, with only minor influence, by other possible configurations of Li. Also in melt grown samples doped with Li to a total concentration as high as 1.5×1019cm−3, a considerable fraction of the Li atoms (at least 20%) is shown to reside on the Zn-site, but despite the corresponding absolute acceptor concentration of ⩾(2–3)×1018cm−3, the samples did not exhibit any detectable p-type conductivity. The presence of LiZn is demonstrated to account for the systematic difference in positron lifetime of 10–15 ps between Li-rich and Li-lean ZnO materials as found in the literature, but further work is needed to fully elucidate the role of residual hydrogen impurities and intrinsic open volume defects.
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Keywords
Li, positron annihilation, vacancy, ZnO
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Citation
Johansen , K M , Zubiaga , A , Makkonen , I , Tuomisto , F , Neuvonen , P T , Knutsen , K E , Monakhov , E V , Kuznetsov , A Y & Svensson , B G 2011 , ' Identification of substitutional Li in n-type ZnO and its role as an acceptor ' , Physical Review B , vol. 83 , no. 24 , 245208 , pp. 1-7 . https://doi.org/10.1103/PhysRevB.83.245208