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報 告 人：陳冠廷
指導老師：林克默 博士
日
期：2010.09.23
Outline
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1. Introduction
2. Experimental procedure
3. Results and discussion
4. Conclusions
Introduction
• In this study, we investigated the influences of gallium
concentration and a rapid thermal annealing process on the
electrical and optical properties of ZnO:Ga (GZO) films
prepared by sol–gel method.
Experimental procedure
• Methanol and zinc acetate were used as start materials.
• Methoxyethanol, which is often used asa solvent and
solubilizing agent in order to achieve better film conductivity,
is purposely avoided because it is known to be toxic and
hazardous.
• Gallium trichloride (GaCl3) served as dopant source to made
the Ga/Zn atomic ratio to be 0.5–5 at.%.
• Monoethanolamine (MEA) with the same molar number as
zinc acetate was added into the sol solution which was then
heated to 50 C, and stirred with a magnetic stones until it was
totally clear. The concentration of solutions was set at 0.3
mol/L.
• The GZO films were deposited by spinning coating on glass
substrates (corning 1737).
• The deposited films were then pre-heated in a RTA furnace for
600 C/10 min.
• The procedures from coating, drying, to first annealing
process were repeated several times so that the sintered films’
thickness could be increased up to the desired value.
• Finally, the films were post-heated in vacuum (~150 mtorr)
for 600 C/1 h.
Results and discussion
Fig. 1 Left: top view of the GZO film; right: cross-section of the
GZO film (1 at.% Ga, 15-layer)
Table 1 Structure properties of the GZO films, Ga/Zn = 0–5
at.%, 15 layers
Fig. 2 X-ray diffraction patterns of ZnO films with different
Gaconcentration, 0.3 mol/L, 15-layer
Fig. 3 Comparison of the thicknesses of the GZO films
measured with SEM and optical methods, 1.0 at.% Ga
Fig. 4 n, μ, ρ in dependence on coating number, 0.3 mol/L,
1.0 at.%Ga
Fig. 5 n, l, q in dependence on Ga concentration, 0.3 mol/L,
15-layer
Fig. 6 Film transmittance with different coating number,
0.3 mol/L, 1.0 at.% Ga
Fig. 7 Film transmittance with different Ga
concentration, 0.3 mol/ L, 15-layer
Conclusions
• In this work, we investigated the influences of gallium
concentration and the infrared heating procedure on thes tructural
as well as opto-electrical properties of the GZO films.
• Experimental results indicate that the RTA process as well as MEA
changed the nucleation and growth behavior of GZO films so that
the RTA-GZO films have higher carrier concentration in comparison
with those prepared by previous fabrication processes .
• Just as expected, Ga, compared with Al, caused less distortion of
ZnO crystal lattices and thus led to higher mobility.
• Moreover, the influence of Ga/Zn ratio on carrier concentration was
not noticeable. On the contrary, excess gallium concentration
significantly reduced carrier mobility due to higher impurity
scattering. The highest conductivity appeared at 1.0 at.% Ga.
• The resistivity of the GZO film was down to 2.20 ×10-3 Ω cm while
the transmittance was over 80%.
“Thanks
for your attention”