The x-ray absorption near edge structures of amorphous ZnO (a-ZnO) films were examined. The near-edge structure, which reflects the virtual electron hopping interactions in the photoabsorption final states, increased in intensity compared to crystalline ZnO. Theoretical path-by-path analyses revealed that this reflects the extinction of the multiple hopping processes found in paths such as ZnOOZn or ZnOZnZn while the Zn–(O or Zn) hopping interactions remain. This suggests that the structural disorders in a-ZnO can induce the localization of the conduction band through the limited hopping interactions.

1.
Transparent Conductive Zinc Oxide: Basics and Applications in Thin Film Solar Cells
, edited by
K.
Ellmer
,
A.
Klein
, and
B.
Rech
(
Springer
,
New York
,
2008
).
2.
K.
Ellmer
,
J. Phys. D: Appl. Phys.
34
,
3097
(
2001
).
4.
A. R.
Hutson
,
Phys. Rev.
108
,
222
(
1957
).
5.
P.
Wagner
and
R.
Helbig
,
J. Phys. Chem. Solids
35
,
327
(
1974
).
6.
H.
Böttger
and
V. V.
Bryksin
,
Hopping Conduction in Solids
(
VCH Verlagsgesellschaft
,
Weinheim, Germany
,
1985
).
7.
H. -H.
Hsieh
and
C. -C.
Wu
,
Appl. Phys. Lett.
91
,
013502
(
2007
).
8.
R.
Martins
,
P.
Barquinha
,
I.
Ferreira
,
L.
Pereira
,
G.
Gonçalves
, and
E.
Fortunato
,
J. Appl. Phys.
101
,
044505
(
2007
).
9.
N.
Mott
,
Conduction in Non-Crystalline Materials
(
Clarendon
,
Oxford
,
1993
).
10.
D. -Y.
Cho
,
J. H.
Kim
,
K. D.
Na
,
J.
Song
,
C. S.
Hwang
,
B. -G.
Park
,
J. -Y.
Kim
,
C. -H.
Min
, and
S. -J.
Oh
,
Appl. Phys. Lett.
95
,
261903
(
2009
).
11.
H. S.
Hsu
,
J. C. A.
Huang
,
Y. H.
Huang
,
Y. F.
Liao
,
M. Z.
Lin
,
C. H.
Lee
,
J. F.
Lee
,
S. F.
Chen
,
L. Y.
Lai
, and
C. P.
Liu
,
Appl. Phys. Lett.
88
,
242507
(
2006
).
12.
A. L.
Ankudinov
,
B.
Ravel
,
J. J.
Rehr
, and
S. D.
Conradson
,
Phys. Rev. B
58
,
7565
(
1998
).
13.
F.
Decremps
,
F.
Datchi
,
A. M.
Saitta
,
A.
Polian
,
S.
Pascarelli
,
A.
Di Cicco
,
J. P.
Itié
, and
F.
Baudelet
,
Phys. Rev. B
68
,
104101
(
2003
).
14.
P. A.
Lee
,
P. H.
Citrin
,
P.
Eisenberger
, and
B. M.
Kincaid
,
Rev. Mod. Phys.
53
,
769
(
1981
).
You do not currently have access to this content.