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Ab INITIO CALCULATIONS OF HYDROGEN IMPURITES
IN ZnO
A. Useinov1, A. Sorokin2, Y.F. Zhukovskii2, E. A.
Kotomin2, F. Abuova1, A.T. Akilbekov1, J.
Purans2 L. N. Gumilyov Eurasian National
University, 3 Munaitpasova, Astana,
Kazakhstan Institute of Solid State Physics, 8
Kengaraga str., University of Latvia, Riga
This study was supported by ERAF project Nr.
2010/0272/2DP/2.1.1.1.0/10/APIA/VIAA/088
Introduction
Details of calculation method
Zinc oxide modified by varios metallic dopants
can be used as suitable low-cost substitute for
indium-tin oxide when manufacturing the solar
batteries and optoelectronic devices 1.
Therefore, the atomic and electronic structure of
defective ZnO continues to attract great
attension due to a number of promising
technological applications. In this study, we
present analyze the influence of neutral H
impurity defects on the redistribution of the
electronic charge, the band structure and energy
of defect in the ZnO bulk. Special attention is
paid to an interstitial hydrogen atom (Hi) 3.
Interstitial and substitutional H have been shown
by first-principles calculations to be shallow
donors, which contribute to the n-type
conductivity in ZnO. When ZnO is doped by H, its
electrical conductivity increases simultaneously
with retain of high optical transparency.
large-scale ab initio DFT calculations have been
performed using the formalism of linear
combination of localized atomic functions (LCAO)
including optimized atomic basis sets combined
PBE0 hybrid exchange-correlation functional, as
implemented into CRYSTAL09 code 2. For periodic
system, The reciprocal space integration was
performed by sampling the Brillouin zone with an
2 2 1 Pack-Monkhorst mesh. To achieve high
accuracy, large enough tolerances of 7, 7, 7, 7,
and 14 were chosen for the Coulomb overlap,
Coulomb penetration, exchange overlap, first
exchange pseudo-overlap, and second exchange
pseudo-overlap, respectively.
To describe the electron density redistribution
we have been constricted a difference charge
density maps projected on characteristic plane of
defect as shown in Fig. 3
Interstitial H in ZnO bulk
In this study the ZnO bulk described with
periodic 3 3 2 supercell models (see Fig.1).
The lattice parameters of supercell a 3.28 and
c 5.18 Å. The H dopants concentration 1.4.
Fig. 3 The total and difference electronic
density distributions for H impurity.
Redistribution of the electronic density to
describe of ground impurity H atom clearly shows
some transfer of charge toward the channel inside
ZnO lattice which contributes to the n type
conductivity in accordance with earlier performed
theoretical study 4, thus electrical
conductivity increase.
Fig. 1. Arrangement of the interstitial hydrogen
atom Hi in the 332 supercell of ZnO
To estimate electronic properties of interstitial
hydrogen atom, we optimize position of Hi per
332 supercell with frozen geometry of lattice.
We have constricted the electronic charge
redistribution (see Fig.3) under influence of H
impurity and density of states (see Fig.2).
b
a

• Conclusions
• Hybrid exchange-correlation functionals provide
  much better correlation of calculated band
  structures with experiment, including width of
  band gap and position of defect levels.
• Our calculations showed that hydrogen creates a
  H-O with O atom and leads to the delocalization
  of electronic charge on the nearest atoms.
• As in earlier studies, we confirm that the
  impurity hydrogen Hi give rise to shallow levels,
  close to the conduction band minimum of ZnO,
  which can explain the increase of the electrical
  conductivity.

Fig. 2. Density of states (DOS) of a perfect (a)
and the one H impurity (b) in ZnO 3 3 2
supercell
Bond length between the oxygen atom and hydrogen
is 1.561 Å. The shift of the hydrogen atom in the
bulk ZnO is x 0.09052 Å  in the opposite
direction of the nearby oxygen atom. For
calculate of defect formation energy we have
consider follow expression Where
defect formation energy, total energy of
defective structure,
energy of a perfect crystal and
energy of isolated H atom. The calculated
formation energy of defect is found to be 1.13
eV.
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C.W. Litton, G. Gantwell, W.C. Harsch, Phys. Rev.
B 60, 2340 (1999). 2. R. Dovesi, V.R. Saunders,
C. Roetti, et al. CRYSTAL-2009 Users Manual
(University of Torino, 2009). 3. Mao-Hua Du and
Koushik Biswas, Phys. Rev. Letters, PRL 106,
115502 (2011) 4. Federico Gallino, Gianfranco
Pacchioni, and Cristiana Di Valentin, J. Chem.
Phys., 133, 144512 (2010)