Surface origin of high conductivities in undoped In2O3 thin films.
The microscopic cause of conductivity in transparent conducting oxides like ZnO, In{2}O{3}, and SnO{2} is generally considered to be a point defect mechanism in the bulk, involving intrinsic lattice defects, extrinsic dopants, or unintentional impurities like hydrogen. We confirm here that the defect theory for O-vacancies can quantitatively account for the rather moderate conductivity and off-stoichiometry observed in bulk In{2}O{3} samples under high-temperature equilibrium conditions. However, nominally undoped thin-films of In{2}O{3} can exhibit surprisingly high conductivities exceeding by 4-5 orders of magnitude that of bulk samples under identical conditions (temperature and O{2} partial pressure). Employing surface calculations and thickness-dependent Hall measurements, we demonstrate that surface donors rather than bulk defects dominate the conductivity of In{2}O{3} thin films.
National Renewable Energy Laboratory, Golden, Colorado 80401, USA.
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S
Lany
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A
Zakutayev
T O
TO
Mason
J F
JF
Wager
K R
KR
Poeppelmeier
J D
JD
Perkins
J J
JJ
Berry
D S
DS
Ginley
A
A
Zunger