Effect of Aluminium Oxide (Al
2
O
3
) surface layers on Tin doped Indium
Oxide (ITO) thin films
Getnet K. Deyu, Hans F. Wardenga, Andreas Klein
Technical University of Darmstadt, Institute of Materials Science, Surface Science Division
Jovanka-Bontschits-Straße 2, D-64287 Darmstadt, Germany
E-mail
We have studied the influence of 1 nm thin Al
2
O
3
layers grown by atomic layer deposition
onto magnetron sputtered Sn-doped In
2
O
3
(ITO) thin films. The film thickness of the ITO
layers was varied from 10-200 nm and substrate temperatures during deposition from room
temperature to 400°C. The samples were analysed using X-ray photoelectron spectroscopy,
4-point conductivity and Hall effect measurements. In addition, 4-point conductivity
measurements in Ar atmosphere during ramping temperature from room temperature up to
500°C and subsequently cooling down to room temperature was conducted. In these
experiments samples with and without Al
2
O
3
were measured simultaneously. The Al
2
O
3
deposition leads to a reduction of the ITO surfaces, which is accompanied by a significant
increase of conductivity for film thickness up to 50 nm and substrate temperatures up to
200°C. ITO films deposited at room temperature show an increase of conductivity by up to a
factor of 2 after Al
2
O
3
deposition. For lower film thickness, the conductivity is comparable to
that of films deposited at 400°C. In contrast to uncoated samples, the conductivity of low
temperature films with Al
2
O
3
coating increased after temperature ramping, which is
associated to a blocking of oxygen incorporation by the Al
2
O
3
film. Thin Al
2
O
3
coatings
therefore offer a new approach to manipulate and stabilize electrical conductivity of TCO
thin films.
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