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Highly transparent solution processed In-Ga-Zn oxide thin films. Y. Wang • S. W. Liu • X. W. Sun • J. L. Zhao • G. K. L. Goh • Q. V. Vu • H. Y. Yu. 指導教授 : 林克默博士 學生 : 董祐成 日期 :99/08/16. Outline. Introduction Experimental Result and Discussion Conclusion. Introduction.
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Highly transparent solution processed In-Ga-Zn oxide thin films Y. Wang • S. W. Liu • X. W. Sun • J. L. Zhao • G. K. L. Goh • Q. V. Vu • H. Y. Yu 指導教授:林克默博士 學生:董祐成 日期:99/08/16
Outline • Introduction • Experimental • Result and Discussion • Conclusion
Introduction • Transparent oxide semiconductors have attracted much attention as a potential active channel layer material for high performance thin film transistors (TFTs). • Compared to the silicon and organic semiconductors,transparent oxide semiconductors have unique advantages. They are transparent in the visible region due to a large bandgap. They also have a high field effect mobility even for an amorphous structure due to the s-electron conduction .
Experimental • The precursor solution for IGZO film was prepared by dissolving 0.1 M of zinc acetate dehydrate [Zn(OAc)22H2O], 0.1 M indium chloride and 0.0025 M gallium chloride (the atom ratio of Ga: In: Zn = 25: 100: 100) in 2-methoxyethanol. • 2. A 0.1 M monoethanolamine (MEA) was then added in the precursor solution as a sol–gel stabilizer.
3. After thoroughly mixing all components, the solution was stirred at 50 ℃ for 2 h and then aged for 24 h. 4. IGZO solution was then spin-coated for 2 times on the prepared substrate at a speed of 3,000 rpm for 30 s and heated at 300 ℃ in the air for 2 min after each coating.
5. Post-annealing was performed at 400 ~ 800 ℃ for 60 s in oxygen ambient by rapid thermal annealing (RTA) to remove the residual chemicals and improve the quality of the IGZO film. The thickness of the IGZO films was about~30 nm in our experiment.
No peaks can be detected from the IGZO films annealed at lower temperatures (400–600 ℃), indicating an amorphous structure. • 2.The films annealed at higher temperatures (700–800 ℃) show a weak broad peak, indicating a nanocrystalline phasebeing formed.
the sheet resistance is the highest at an intermediate annealing temperature (600 ℃). • It is worth mentioning that, although nanocrystalline phase tends to have a lower mobility through grain boundary scattering, the mobility may not be directly correlated to the nanocrystallite size as the crystal phase (amorphous or nanocrystalline) also affects the mobility. • 3. In our study here, both the mobility and nanocrystallite size increases with the annealing temperature.
the IGZO films are highly transparent in the visible range (400–700 nm) with a transparency of more than 90% for films annealed with a temperature higher than 600 ℃. And the transparency is more than 75% for all films in the range of 300–900 nm.
Conclusion • In conclusion, we have fabricated highly transparent IGZO thin films by solution method using acetate-and chloratebased precursors. • 2.The IGZO films show a phase change from amorphous to nanocrystalline with the increase of the post-annealing temperature. Compared to the nitrate-based IGZO precursor, the chlorate-based precursor increases the phase change temperature of IGZO thin films to 600–700 C.
3. The 600 ℃ annealed IGZO films showed a sheet resistance of 8.4 x 1010 ohm/square and a carrier concentration of 1.9 x 1013 cm-3, which is the most suitable for TFT channel in our experiment.
