Electronic processes in doped ZnO nanopowders and transparent ceramics
L.Grigorjeva
1
, K.Smits
1
, A.Zolotarjovs
1
, E.Gorokhova
2
, S. B. Eron’ko
2
, P.Rodnyi
3
,
K.Chernenko
3
1
Institute of Solid State Physics, University of Latvia, Riga, Latvia
2
JSC "RTIOM RSC " S.I.Vavilov SO, Saint-Petersburg, Russia
3
State Polytechnical University, Saint-Petersburg, Russia
E-mial:
The luminescence spectroscopy is useful for the investigation the doping processes in ZnO.
The present study is devoted to electronic processes in ZnO nanocrystals (NC) and
transparent ceramics undoped and doped with In or Ga.
The excitonic and donor-acceptor pair (DAP) luminescence at the low temperatures were
studied and analysed. The shallow electron and hole traps are responsible for DAP
luminescence with maxima at 3.21 eV and existence of these traps is very important for
conductivity mechanisms. We use the radioluminescence and thermostimulate luminescence
(TSL) methods for the analysis of the shallow traps in ZnO. The activation energies for the
traps for different ZnO materials including ZnO crystals were obtained from TSL glow
curves.
The ZnO NC was prepared by solar physical vapour deposition (SPVD) method [1]. The
method allows preparing ZnO NC in tetrapod form; the doping was done during SPVD
process. Transparent ZnO ceramics were prepared in two stages: first, the powder was
pressed in air under 12MPa during 15 min and the second stage is hot pressing in vacuum at
temperature ~1000
o
C under pressure 100-200 MPa for 60 minutes [2].
Radioluminiscence spectra were measured at 8K the positions of ExD
0
, 1LOEx, DAP and its
phonon replicas were obtained for studied samples. The ratio of luminescence intensities of
ExD
0
and deep level defect luminescence were analysed.
In ZnO single crystal the main TSL peak is in temperature region 30-50K with thermal
activation energy ~30 meV. The spectrum of this TSL peak is peaking at ~600 nm and its
origin is defect recombination. In ceramics and NC the TSL and its spectra were studied for
shallow traps identification. The models of electronic processes in ZnO are proposed.
Acknowledgments
This project has received funding from the European Union Seventh Framework Programme
for research technological development and demonstration under grant agreement no 312643
and ERANET-RUS ID N360.
References
[1] K.Smits, L.Grigorjeva, D.Millers, K.Kundzins, R.Ignatans, J.Grabis., C.Monty. Opt.Mat.
2014, v.37, 251-256.
[2] P.A.Rodnyi, E.I.Gorokhova, K.A.Chernenko, I.V.Khoduk. IOP Conf.Series: Mater.
Sci.and Engin. 2012, v.38, 012002.
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