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報 告 人：王禮國
指導老師：林克默 博士
日
期：2010.08.16.
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Outline
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1. Introduction
2. Experimental procedure
3. Results and discussion
4. Conclusions
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Introduction
• Transparent conductive Al-doped ZnO films were deposited by
the sol–gel method. The growth mechanism of the film
microstructure and its influences on the electrical properties
were discussed.
• Zinc oxide and doped zinc oxide films have received extensive
attention in recent years due to their excellent optical and
electrical properties .
• Several deposition methods such as sputtering technique
pulsed laser deposition,thermal plasma,MOCVD,spray
pyrolysis and sol–gel method have been investigated and
compared for deposition of the AZO films.
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Experimental procedure
In our experiments, Zinc acetate dihydrate was used as a
starting material,lsopropyl alcohol and aluminum nitrate
served as the solvent and dopant sources, respectively.The
Al/Zn ratio in the solution was varied from 1% to 4%.The
solution concentration was 0.3 and 0.5 mol/l.
After being deposited on glass by dip-coating,the films
were first dried at 70 °C for 10 min to evaporate the solvent
partially.After wards, the films were heated in a furnace at
500–700 °C for 1 h in air (pre-heat treatment).
The procedures from coating, drying, to annealing were
repeated 2–5 times so that the sintered film thickness could
be up to 400 nm. These films were then annealed in vacuum
(∼ 1 mtorr) at 500–700 °C for 1 h (post-heat treatment).
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X-ray diffraction patterns of AZO films in
dependence of the number of layers, 0.5
mol/l, Al/Zn=1 at.%.
The relative intensity changes of the
(002) peaks indicated that the
preferred growth orientation of ZnO
crystal was restrained by the film itself.
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Due to the growth mechanism, the
samples' crystallite size grew slightly along
with the increasing number of film layers. In
contrast, the Al concentration affected the
crystallite size considerably.
Film resistivity versus layer number under
different procedure conditions.
Pre-heat treatment 600 °C, 0.3 mol/l open
symbols, 0.5 mol/l closed symbols.
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Samples’lattice deformation versus layer
number , the samples were
preheated by 600 °C in air, and post heated by
600 °C under vacuum (∼1 mtorr).
Comparison of film transmittances, 5 layers.
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Conclusions
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In this study, it was found that the c-oriented growth of ZnO crystal was disturbed during
the multi-layered dip-coating process. This process did not enable the crystallite size to grow
obviously, but it could allow crystallite and Al atoms to find the suitable positions and led to a
better film quality. The change of the microstructures affected the carrier concentration more
considerably than the carrier mobility.
The higher dopant concentration led to smaller crystallite size. We also found that the
effective Al concentration of AZO films was much lower than the dopant concentration. This
agreed well with the measured carrier concentration. It means that most of the Alatoms did
not replace the lattice positions of the Zn atoms. Thus, we believe that film conductivity can
be enhanced by way of the well directed growth and the controlling of the dopant distribution.
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Thank you for your attention
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