The Structure and properties of amorphous p-type ZnO-IrO
2
thin films
J. Purans
1
, M. Zubkin
1
, J. Gabrusenoks
1
, G. Cikvaidze
1
, R. Kalendarev
1
, A. Azens
1
, A.
Zitolo
2
, K. Pudzs
1
, A. Anspoks
1
1
Institute of Solid State Physics, University of Latvia, Riga, Latvia
2
Synchrotron SOLEIL, l'Orme des Merisiers, Saint-Aubin, Gif-sur-Yvette, France
E-mail
Although doped ZnO thin films are promising
n
-type TCO materials, obtaining
p-
type
ZnO thin films is an important milestone in the development of transparent electronics [1,2].
In this work we will summarize our research on the ZnO-IrO
2
thin films [3,4] and compared
with the published theoretical models [5,6].
A series of amorphous and nano-crystalline p-type and n-type ZnO-IrO
2
thin films
were deposited on solid (glass, Si,Ti) and flexible substrates by reactive DC magnetron co-
sputtering at RT and 300°C. The amorphous to nano-crystalline transition and the structure of
ZnO-IrO
2
thin films were investigated by X-ray diffraction, Hall transport and Seebeck
measurement, UV-VIS, Raman and Infrared spectroscopies. Moreover, femtometer accuracy
in the determination of interatomic distances is now attainable [7,8], therefore additional
information on the structure can be obtained from EXAFS and XANES spectra measured at
the Synchrotron Radiation facility (SOLEIL, France).
A model of the amorphous ZnO structure as a diamond-like network of ZnO
4
tetrahedra is suggested, while the amorphous ZnO-IrO
2
structure is suggested as penetrated
networks of distorted ZnO
4
and IrO
6
polyhedra. Finally at high concentration of IrO
2
, the
structure is a rutile-like network of IrO
6
octahedra. Mechanisms for the transport properties
(n- and p-type) observed in the amorphous and nano-cristalline thin films will be presented,
highlighting a structure-property and iridium valence states relationships. These models will
be compared with the structural models of a-ZnO-SnO
2
and a-ZnO-In
2
O
3
.
References
1. K. Ellmer, Nature Photonics 6, 809 (2012).
2. E. Fortunato, D. Ginley, H. Hosono and D. C. Paine, MRS Bulletin 32, 242 (2007).
3. M. Zubkins, R. Kalendarev, J. Gabrusenoks, K. Vilnis, A. Azens and J. Purans, Phys. Status Solidi C 11,
1493 (2014).
4. M. Zubkins, R. Kalendarev, J. Gabrusenoks, K. Smits, K. Kundzins, K. Vilnis, A. Azens and J. Purans, IOP
Conf. Series: Materials Science and Engineering 77, 012035 (2015).
5. Dekkers M, Rijnders G and Blank D G A 2007 Appl. Phys. Lett. 90 021903
6. D. M. Ramo and P. D. Bristowe, J. Chem. Phys. 141, 084704 (2014).
7. J.Purans, N. D.Afify, G.Dalba, R.Grisenti, S.De Panfilis, A.Kuzmin, V.I.Ozhogin, F.Rocca, A.Sanson, S. I.
Tiutiunnikov, P.Fornasini, Phys.Rev.Lett., 100, 00055901 (2008).
8. J. Purans, P. Fornasini, S. E. Ali, G. Dalba, A. Kuzmin, and F. Rocca, Phys. Rev. B 92, 014302 (2015).
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