Highly transparent solution processed In-Ga-Zn oxide thin films 指導教授 : 林克默博士 學生 : 董祐成 日期 :99/08/16 Y. Wang S. W. Liu X. W. Sun J. L. Zhao G. K. L. Goh Q. V. Vu H. Y. Yu

Outline Introduction Experimental Result and Discussion Conclusion

Introduction 1.Transparent oxide semiconductors have attracted much attention as a potential active channel layer material for high performance thin film transistors (TFTs). 2.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 1.The precursor solution for IGZO film was prepared by dissolving 0.1 M of zinc acetate dehydrate [Zn(OAc) 2 2H2O], 0.1 M indium chloride and 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.

Result and Discussion

1.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.

1.the sheet resistance is the highest at an intermediate annealing temperature (600 ℃ ). 2.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 1.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 ohm/square and a carrier concentration of 1.9 x cm -3, which is the most suitable for TFT channel in our experiment.

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