Indium tin oxide (ITO) thin films were deposited on polymeric substrates at room temperature by dc reactive magnetron sputtering from an In–Sn (90–10 wt%) alloy target. The electrical, optical, and mechanical properties of ITO films on various substrates such as polycarbonate, acrylic, polyethylene terephthalate, and glass are influenced sensitively by sputtering parameters. Therefore, the dependence of these properties on dc power, working pressure, and partial oxygen content has been systematically investigated. Low dc power was applied to avoid the deformation of polymeric substrates. The electrical resistivity of as-deposited ITO films decreases initially and then increases as oxygen partial pressure (PO2) increases. The optical transmittance at visible wavelength of 550 nm was as much as 85%. The friction force of as-deposited ITO films on various substrates is increased with an increase of dc power, and behaves similarly to the optimum curve of resistivity with increasing PO2.
In this study, the effects of microwave annealing (MWA) on the electrical properties of amorphous In-Ga-Zn-O thin-film transistors (a-IGZO TFTs) are evaluated. To measure the transfer and output characteristics of as-deposited, conventional thermal annealed (CTA), or microwave annealed TFTs, the devices are fabricated by varying the compositional ratios of IGZO films (In 2 O 3 :Ga 2 O 3 :ZnO ¼ 1:1:1, 1:1:2, and 2:1:2 at%). The reliability is evaluated by measuring the threshold voltage shift under the gate bias stress and by analyzing the charge trapping characteristics according to the operating temperature. In addition, the interface trap density of the a-IGZO channel/ gate insulator and the volume density of the shallow trap of the channel layer are extracted to evaluate the difference in trap density according to the channel composition and the variation in the trap density as a result of the annealing process. Lastly, the sub-gap density of states (DOS) of the TFTs is investigated to verify the compositional ratio and the annealing effect on the electrical characteristics and reliability of the devices. Based on these results, it is demonstrated that high-performance a-IGZO TFTs can be fabricated by using the low thermal budget MWA technique and by controlling the composition of the IGZO channel.
In this study, an optimized post-deposition heat treatment method is investigated to improve the electrical, optical, and structural properties of indium-tin-oxide (ITO) thin films applied to transparent electrodes in nextgeneration displays. In order to improve the properties of ITO thin films, heat treatment is performed using conventional thermal annealing (CTA), rapid thermal annealing (RTA), and microwave annealing (MWA). To evaluate the effect of MWA on the ITO thin film, the electrical, optical, and structural characteristics of the thin film are analyzed and compared with those of the films annealed by traditional CTA and RTA. The results show that the electrical and optical characteristics of the ITO thin film improve with the increase in microwave power. In particular, the sheet resistance of the ITO thin film reduces to 4 Â 10 2 Ω sq À1 , despite the microwave power of 250 W and short heat treatment duration of 2.5 min by MWA. In addition, the optical transmittance of the ITO thin film in the visible region increases to 89.5%, superior to the transmittance before heat treatment of 87.5%.
In this paper, we investigate a low thermal budget post-deposition-annealing (PDA) process for amorphous In-Ga-ZnO (a-IGZO) oxide semiconductor thin-film-transistors (TFTs). To evaluate the electrical characteristics and reliability of the TFTs after the PDA process, microwave annealing (MWA) and rapid thermal annealing (RTA) methods were applied, and the results were compared with those of the conventional annealing (CTA) method. The a-IGZO TFTs fabricated with as-deposited films exhibited poor electrical characteristics; however, their characteristics were improved by the proposed PDA process. The CTA-treated TFTs had excellent electrical properties and stability, but the CTA method required high temperatures and long processing times. In contrast, the fabricated RTA-treated TFTs benefited from the lower thermal budget due to the short process time; however, they exhibited poor stability. The MWA method uses a low temperature (100 °C) and short annealing time (2 min) because microwaves transfer energy directly to the substrate, and this method effectively removed the defects in the a-IGZO TFTs. Consequently, they had a higher mobility, higher on-off current ratio, lower hysteresis voltage, lower subthreshold swing, and higher interface trap density than TFTs treated with CTA or RTA, and exhibited excellent stability. Based on these results, low thermal budget MWA is a promising technology for use on various substrates in next generation displays.
We constructed complementary inverters utilizing solution-processed semiconducting single-walled carbon nanotube (scSWCNT) random networks and electrospun In-Ga-Zn-O (IGZO) nanofibers as p-type and n-type thin-film transistor (TFT) channels, respectively. The IGZO nanofiber n-type TFT and scSWCNT random network p-type TFTs show an on-off current ratio of 2.82 × 105 and 1.38 × 105, a threshold voltage of −7.60 and 9.50 V, a subthreshold swing of 380.13 and 391.01 mV/dec, and field effect mobilities of 1.96 and 5.67 cm2/V s for electrons and holes, respectively. In addition, these hybrid-type inverters consisting of n-channel TFTs and p-channel TFTs exhibit excellent complementary metal-oxide-semiconductor (CMOS) operation. Therefore, we expect that the hybrid CMOS-type inverters based on scSWCNT random networks and IGZO nanofibers can be innovative electronic devices for transparent and flexible digital logic circuits.
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