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We studied the effect of X-ray irradiation on the negative threshold voltage shift of bottom-gate a-IGZO TFT. Based on spectroscopic analyses, we found that this behavior was caused by hydrogen incorporation and oxygen vacancy ionization.

We have developed roll printing process for low cost TFT LCD fabrication. Pattern position accuracy which is the most important issue for successful printing process could be improved by remodeling the blanket structure and the physical property of PDMS. Through improving printing pattern accuracy, we were able to print all layers of TFT and CF on substrates and a 15 inch XGA TFT LCD panel adopting TN mode was successfully fabricated.

We report on a characterization method to quantitatively estimate the interfacial trap density of states (DOS) in thin-film transistors (TFTs): photon-probe capacitance-voltage (CV ) measurement. The photo-CV method was compared to photoexcited charge-collection spectroscopy, which is another photon-probe method using current-voltage (I-V ) measurement to meet the same purpose. Here, we directly characterized the DOS of amorphous-Si-and amorphous-InGaZnO-based TFTs using the photon-probe CV measurement, and the results turned out to mainly focus the trap DOS at channel/dielectric interface. On the one hand, the DOS profile by photon-probe I-V method appeared to give additional trap information from the transistor back channel. Index Terms-Amorphous InGaZnO (a-IGZO), amorphous Si (a-Si), density of states (DOS), thin-film transistor (TFT).