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Mid-Gap Electronic States in Zn1-xMnxO.
Physical Review B (2010)
  • C. A Johnson
  • Kevin R. Kittilstved, University of Massachusetts - Amherst
  • T. C Kaspar
  • T. C Droubay
  • S. A Chambers
  • G. M Salley
  • D. R Gamelin

Electronic absorption, magnetic circular dichroism (MCD), photoconductivity, and valence-band x-ray photoelectron (XPS) spectroscopic measurements were performed on epitaxial Zn1−xMnxO films to investigate the origin of the mid-gap band that appears upon introduction of Mn2+ into the ZnO lattice. Absorption and MCD spectroscopies reveal Mn2+-related intensity at energies below the first excitonic transition of ZnO, tailing well into the visible energy region, with an onset at ∼2.2 eV. Photoconductivity measurements show that excitation into this visible band generates mobile charge carriers, consistent with assignment as a Mn2+/3+ photoionization transition. XPS measurements reveal the presence of occupied Mn2+ levels just above the valence-band edge, supporting this assignment. MCD measurements additionally show a change in sign and large increase in magnitude of the excitonic Zeeman splitting in Zn1−xMnxO relative to ZnO, suggesting that sp-d exchange in Zn1−xMnxO is not as qualitatively different from those in other II-VI diluted magnetic semiconductors as has been suggested. The singular electronic structure feature of Zn1−xMnxO is the presence of this Mn2+/3+ ionization level within the gap, and the influence of this level on other physical properties of Zn1−xMnxO is discussed.

Publication Date
Publisher Statement
Doi:10.1103/PhysRevB.82.115202 Copyright 2010 by The American Physical Society.
Citation Information
C. A Johnson, Kevin R. Kittilstved, T. C Kaspar, T. C Droubay, et al.. "Mid-Gap Electronic States in Zn1-xMnxO." Physical Review B Vol. 82 Iss. 11 (2010)
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