Probing charge carrier density in a layer of photodoped ZnO nanoparticles by spectroscopic ellipsometry

G. Lakhwani, R.F.H. Roijmans, A.J. Kronemeijer, J. Gilot, R.A.J. Janssen, S.C.J. Meskers

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Abstract

Changes in the optical constants of a layer of ZnO nanoparticles (5 nm diameter) induced by UV illumination in O2-free atmosphere are determined by using spectroscopic ellipsometry. The onset of optical absorption of ZnO shifts to higher photon energy after illumination. This is interpreted in terms of a Moss-Burstein shift. From the magnitude of the shift, the charge carrier density in the conduction band after UV illumination was determined to be 2 × 1019 cm-3, about one carrier per particle. Kelvin probe measurements give a lower limit for the density of 1018 cm-3. The free carrier density after illumination is high enough to explain the formation of quasi-ohmic contacts between ZnO and the polymeric p-type conductor poly(3,4-ethylenedioxythiophene) (PEDOT).
Original languageEnglish
Pages (from-to)14804-14810
Number of pages6
JournalJournal of Physical Chemistry C
Volume114
Issue number35
DOIs
Publication statusPublished - 2010

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