In this work, the influence of copper on amorphous type Indium-Gallium-Zinc-Oxide (a-IGZO) thin-film transistor's (TFTs) transfer curve is studied. The I D -V G curves of a-IGZO TFTs with source/drain in the structures of Cu/Ti and Ti/Al/Ti are compared. The results show that the copper greatly deteriorates the performance of the TFTs. The presence of the copper in the channel region of the device is verified by SIMS analysis. A Cu-dipping experiment is conducted by dipping devices into the solution of CuSO 4 to confirm the role of copper in the deterioration of the I D -V G curves. The hypothesis is also verified through ATLAS device simulator.Indium-Gallium-Zinc-Oxide (a-IGZO) thin-film transistors (TFTs) have attracted great attention for the impressive transparent and high carrier mobility characteristics. They can serve in switching pixel or peripheral circuit application for active-matrix liquid crystal displays (AMLCDs) in the next generation. 1, 2 With the increase of display size, resolution, and the operating frequency in television and 3D display, Cu is applied to replace Al for the reduction of resistance loading in the signal metal bus. Many attempts have been made to incorporate Cu into the amorphous silicon TFT array fabrication. [3][4][5] The process implementation of using Cu as the source/drain (S/D) metal of a-IGZO TFT is also an interesting topic to study. However, most of the previous papers about a-IGZO TFT with the application of Cu emphasized on the contact resistance and the quality of the surface between Cu and a-IGZO. 6-10 In the present work, the influence of Cu diffusion to the electrical properties of a-IGZO TFT is observed and studied. Device and ExperimentThe experimental work was based on the bottom-gate TFT devices of back-channel-etch (BCE) structure with symmetrical S/D fabricated on the glass substrate. Shaped Ti/Al/Ti (50/200/50 nm) gate electrodes were capped with 400-nm-thick SiNx gate dielectric, which was deposited by plasma enhanced chemical vapor deposition (PECVD) at 370 • C. The active layer of 60-nm-thick a-IGZO film was deposited by DC magnetron sputtering system using a target of In:Ga:Zn = 1:1:1 in atomic ratio with the O 2 /Ar ratio about 6%. For the S/D metals, both samples of Ti/Al/Ti (50/200/50 nm) and Cu/Ti (200/50 nm) were prepared by DC sputtering at room temperature. Then, the devices are capped with passivation at 280 • C as protection layer to avoid the disturbance of outside surrounding. After that, via holes and ITO were patterned and shaped for device measurement. The final annealing step was conducted at 280 • C for 1 hour in the oven. In this study, the electrical characteristics are measured by Agilent 4156-C system at 25 • C in dark under 1 atmosphere pressure. The threshold voltage (V T ) is defined by the gate voltage (V G ) when the size-normalized drain current I D reaches 10 −9 A. The subthreshold swing (S.S) and effective field mobility (μ) are extracted at drain voltage V D = 1V. Transfer CharacteristicsFigure 1a and 1b show the electrical ...

Abstract-A dual-gate amorphous InGaZnO 4 (a-IGZO) thinfilm transistor (TFT) has two gate electrodes. The primary gate electrode is at the bottom, and the other is on the top. The drain current of the TFT can be controlled by both the bottom and top gates. This phenomenon provides great flexibility for the circuit design. In this letter, we propose the differential amplifier circuit using the top gate of the dual-gate a-IGZO TFT as an input for positive feedback to boost the gain. It is experimentally verified that the gain of the differential amplifier circuit is increased three times larger than those without the feedback loop.Index Terms-Differential amplifier circuit, dual-gate amorphous InGaZnO 4 (a-IGZO) thin-film transistor (TFT).

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In addition to the gate electrode at the bottom, a dual-gate InGaZnO 4 (a-IGZO) thin film transistor (TFT) has a secondary gate electrode on the top. The threshold voltage of the TFT using the bottom-gate in its normal operation can be controlled by the top-gate. Based on this phenomenon, a new concept of using the top-gate to compensate threshold voltage variation is proposed. This new technique is demonstrated in two pixel circuits of active-matrix organic light-emitting diode and verified by the measurement results.

We have measured the pitch of cholesteryl propionate-nonanoate mixture at different weight ratio for various temperature. The pitch of ternary mixture, cholesteryl propionate, nonanoate and myristate, was also measured as a function of temperature and concentration of cholesteryl myristate when the weight ratio of propionate and nonanoate is kept equal. The molar twisting power (p) was calculated by employing Bak and Labes' equation and the relation between twisting power and temperatures is found to be linear for cholesteryl propionate, nonanoate and myristate in the temperature range away from transitions.For the mixture with smectic mesophase the temperature coefficient of the pitch is anomalous. The v (critical exponent describing the divergence of the smectic correlation length) for cholesteryl nonanoate is found to be 0.611 which is in excellent agreement with de Gennes' prediction. I NTR 0 DU CTlO NIt is well known that the pitch of cholesterics can be changed by pressure, temperature and concentration. In the binary mixture of the cholesteric liquid crystal, the relation between pitch, temperature and concentration has been investigated by many auth01-s.'~~ Chen and Chou8 also had calculated the molar twisting power of cholesteryl propionate and acetate by using the equation derived by Bak and Labes. They found that the molar twisting power is linear in temperature for the temperature range which is away from the transitions. The dependence of pitch on concentration had been studied theoretically by many people.9P13 Bak