We have studied the effect of thickness on the structural, optical and electrical properties of
In2O3:Sn (ITO) thin films. Two series of ITO thin films have been deposited onto glass
substrates by DC sputtering at two
partial pressures of oxygen (ppo): 4 × 10−4
and 4.75 × 10−4 mbar.
Each series consists of samples with
thickness ranging from 306 nm to 1440 nm. We observed a
change of texture with thickness; the
thinner films grow with a 〈111〉
preferred orientation;
however as the thickness increased,
the preferred orientation becomes in the
〈100〉 direction.
The lattice constant and the grain
size have also been obtained from the X-ray spectra. The
energy gap, Eg,
has been obtained from the transmission curve;
Eg is found to decrease with
increasing thickness for both series.
The electrical resistivity ρ has been studied as a function of
thickness, ppo and temperature (T).
The temperature was varied from room temperature (RT)
to
450 °C and back to RT;
a hysteresis effect was observed in the ρvs.T
curve. Also, a minimum
in ρ was observed, in all these samples,
in the temperature range 260 to 280 °C. For these
temperatures, we have studied the effect of annealing time on the electrical resistivity for
samples having both textures. We noted that ρ increased with annealing time and reaches a
saturation value equal to the RT temperature value.
Hall effect experiments were done on all
these samples. The concentration n and the mobility μH were obtained. These parameters are
found to be sensitive to the thickness and the texture of these films. All these results will be
correlated and discussed.