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With in-depth analysis and the exact conduction mechanism, the oxide thin-film diodes were developed by ALD-assisted interface engineering.

We scrutinized the barrier capability of SiOx, plasma Al2O3 (P-Al2O3)/SiOx, and SiNx/SiOx passivation layers (PLs) on the environmental stabilities of back-channel etched Al-doped InSnZnO (Al-ITZO) TFTs at 85 °C with a relative humidity of 85 % for 30 days. Turn-on voltage (VON) of SiNx/SiOx-passivated TFTs was dramatically shifted to the negative direction and became conductive. Compared to those of SiOx and P-Al2O3/SiOx films, more hydroxyl groups existed at the PL/active interface of SiNx/SiOx-passivated Al-ITZO films. Water vapor transmission rates showed that abnormal behavior was not attributed to barrier capability of PL against the water vapor. When all TFTs were kept at 85 °C for 30 days in an air-drying oven, only the VON of SiNx/SiOx-passivated TFTs shifted negative direction and finally became conductive. Secondary ion mass spectroscopy (SIMS) results revealed that this abnormal behavior originates from the formation of oxygen vacancy due to highly existed hydroxyl group at SiOx/Active interface at an elevated temperature.

Flexible and wearable pressure sensors, which can detect various pressures generated by the human body and convert them into electrical signals, are of great interest because they have a wide variety of applications for an interface between humans and external devices. Elastomeric dielectric materials for commercial piezocapacitive pressure sensors need to be manufactured quickly and easily via cost-effective methods. Herein, we report a piezocapacitive pressure sensor based on a three-dimensional macroporous dielectric layer fabricated by a rapid and facile baking-inspired foaming process. The pressure sensor showed high sensitivities of 0.16 ± 0.03 kPa−1 (at

We report how the intrinsic film stress of Mo source and drain (S/D) electrodes affects the electrical properties of Al doped InZnSnO thin-film transistors (TFTs). By controlling the Ar pressure during the sputtering process, Mo films with different film stresses (1948.2 MPa and 168.8 MPa) were formed. Two kinds of TFTs were fabricated applying these films as S/D electrodes. The TFTs made with the high-stress S/D showed linear mobility ( $\mu _{\text {lin}}$ ) of 29.44 cm2/Vs and hysteresis of 3.39 V while the TFTs with the low-stress S/D showed $\mu _{\text {lin}}$ of 35.25 cm2 /Vs and hysteresis of 1.97 V. Under positive bias temperature stress (1 MV/cm, 60°C, 3600 s), $\text{V}_{\text {on}}$ was 4.48 V and 7.28 V for the TFTs with the low-stress S/D and high-stress S/D, respectively. X-ray photoelectron spectroscopy and finite element (FE) simulation results revealed that oxygen deficient sites in the active layer generated by the film stress of the Mo S/D induced degradation of the device characteristics.

Highly sensitive and flexible pressure sensors were developed based on dielectric membranes composed of insulating microbeads contained within polyvinylidene fluoride (PVDF) nanofibers. The membrane is fabricated using a simple electrospinning process. The presence of the microbeads enhances porosity, which in turn enhances the sensitivity (1.12 kPa

The fingerprint recognition has been widely used for biometrics in mobile devices. Existing fingerprint sensors have already been commercialized in the field of mobile devices using primarily Si-based technologies. Recently, mutual-capacitive fingerprint sensors have been developed to lower production costs and expand the range of application using thin-film technologies. However, since the mutual-capacitive method detects the change of mutual capacitance, it has high ratio of parasitic capacitance to ridge-to-valley capacitance, resulting in low sensitivity, compared to the self-capacitive method. In order to demonstrate the self-capacitive fingerprint sensor, a switching device such as a transistor should be integrated in each pixel, which reduces a complexity of electrode configuration and sensing circuits. The oxide thin-film transistor (TFT) can be a good candidate as a switching device for the self-capacitive fingerprint sensor. In this work, we report a systematic approach for self-capacitive fingerprint sensor integrating Al-InSnZnO TFTs with field-effect mobility higher than 30 cm2/Vs, which enable isolation between pixels, by employing industry-friendly process methods. The fingerprint sensors are designed to reduce parasitic resistance and capacitance in terms of the entire system. The excellent uniformity and low leakage current (−12) of the oxide TFTs allow successful capture of a fingerprint image.

As personal mobile devices have been improved and concept of IoT has been introduced into every objects as well as computers or tablet PCs, the importance of security for personal information has surfaced as a serious issue. For that reason, many related industries have been taking profound interests in fingerprint verification technology. One of the most attractive research should be manufacturing capacitive-typed fingerprint sensor array which is transparent and able to be embedded in the touch panel. The fingerprint sensor based on oxide thin film transistor (TFT) array is one of the solution for the high resolution and high speed operation. Furthermore, this transparent oxide TFT array has price competitiveness due to the simple structure and can be successfully adopted to the flexible IoT devices in comparison to the semiconductor technology based on the silicon. Since capacitive-typed high speed operation fingerprint sensor array consists of 500 ppi resolution pixels with one TFT and one capacitor, low resistance transparent electrode are essential to obtain high transparency. Well-known transparent electrode material, Indium-Tin-Oxide (ITO), has 10Ω/sq of sheet resistance at 150nm-thick that may not be enough to manufacture fingerprint sensor array embedded in the display panels. Representative low-resistance metal, Ag, has difficulty in use not only for electrode of oxide TFT but the sensing electrode due to its low transparency. Within the level that its transparency satisfies requirement, however, inserting Ag layer between both sides of ITO layers definitely helps resistance decreases. For the reduction of capacitance within the array, minimum width of electrode patterns used for the fingerprint sensor array is less than 5㎛ and dry etching process plays a vital role in patterning ITO/Ag/ITO triple layers. Although ITO and Ag can be etched in the same way by dry gas based on Cl, the difference on etch rates of the two materials possibly generates some problem like Ag exposure at the side of etched profile. It can surely cause a great change on the final properties of TFTs, and that is the reason why dry etching process should be a core technology in this case. As mentioned above, Cl2 and Ar are mainly used as etching gas for both ITO and Ag in this study [1], but their etch rates are greatly different from each other. We found out that ITO had been etched five times faster than Ag, so that a protrusion of Ag edge had been inevitable from the ITO edge during the triple dry etching sequences although we had put only 10nm-thick Ag in the middle. To solve this problem, we used two methods mostly to modify dry etching recipe for removing by-product that might be formed by Ag exposure in air; one is using O2 gas instead of Ar as a base gas during main etching, especially later in the process, the other is insertion of additional ashing step with O2gas after the main etching process. In this study, we fabricated top gate structured TFT applied with ITO/Ag/ITO triple stack as a source/drain in order to verify good characteristics of the triple layers as transparent electrode. As described above, we developed the dry etching conditions which didn’t have a bad effect on contact property, and also confirmed final characteristics of the top gate structured TFT. This top gate structured TFT included Indium-Gallium-Zinc-Oxide (IGZO) as an active layer and Al2O3as a gate insulator. TFT post annealed at 300℃ showed mobility, Von, S.S, and hysteresis of 15.6㎤/V.s, 0.3V, 0.1V/dec., and almost 0V, respectively, and moreover, study on stability and analysis depending on various dimensions of TFT channel will be proceeded. Furthermore, we are currently working on analysis of stacked films by TEM to investigate Ag film which may be degenerated during post annealed process or oxidized by exposure in air. Obtaining outstanding TFT properties with ITO/Ag/ITO triple stack as a source/drain layer means that we developed etched profile which does not influence TFT operation at all, and what is more, it can stand comparison with other transparent materials applied to fingerprint sensor embedded display panel. Besides, totally transparent high resolution transistor array will be fully valuable for new transparent display application such as augmented reality. [1] Y.J. Lee, S.D. Park, B.K. Song, S.-G Kim, H.-H, Choe, M.-P. Hong and G.-Y, Yeom, Jpn. J. Appl. Phys., Vol. 42 (2003) pp.286-290 This work was supported by Open Innovation Lab Project from National Nanofab Center (NNFC).

Human tissues are exposed to various mechanical stimuli, and the types and magnitudes of the mechanical stimuli acting on cells and tissues are important factors in controlling the development pathway of cells and tissues. Therefore, giving repetitive mechanical stimuli to culturing cells may provide beneficial effects, such as differentiating target cells or accelerating cell development, by controlling the type of stimulus and its magnitude. Electroactive polymers (EAPs) respond to electrical voltage with significant changes in shape or size and can transfer appropriate (1–20%) mechanical stimuli to cells. In this study, we designed a new type of flexible cell culture device made of silicone (composite) film, and evaluated the actuating strain of the driving portion of the cell culture device according to the pre-stretching condition and the clay nanoparticle (i.e., organically modified montmorillonite, or OMMT) content. The effect of OMMT particles on the electro-mechanical performance of the silicone (composite) film actuators was investigated by adding 0–5% OMMT particles to silicone elastomer using the solvent-assisted mixing method. The effects of these two major variables on actuation strain were quantitatively investigated, and the most appropriate conditions for the driving part of a cell culture device were determined.

Dyeing of a poly(vinyl alcohol) (PVA) film with a high degree hydrolysis (>98%) using Direct Black 22, adichroic organic dye, was investigated under various conditions (dye concentration, salt (Na 2 SO 4 ) concentration, andtemperature). This process could correctly be analyzed using the Freundlich isotherm ( C film =K F C soln1/n ) based on the poremodel. The Freundlich exponent 1/n appeared to be constant over a broad range of salt concentrations, but the Freun-dlich constant K F assumed the maximum value for [Na 2 SO 4 ]=~0.010 M. However, this value was 10 times greater thanthat under the no-salt conditions. Analysis of the adsorption kinetics revealed that only the early stage of dyeing was fol-lowed second-order, with an activation energy of 50.2 kJ/mol. However, gradual deviation from the second-orderoccurred with an increase in the dyeing time. These results indicated that the surfaces of the inner pores in the PVA filmare dyed through multilayer adsorption, which is accompanied by complicated kinetics.Keywords: poly(vinyl alcohol), dichroic dye, dyeing, Freundlich's isotherm, pore model, the second-order kinetics

To achieve the next generation displays, it is becoming increasingly important to develop backplane technology with superior characteristics such as high mobility, high stability, and high transparency. Among the several candidates for suitable backplane in high definition display, amorphous In-Ga-Zn-O (a-IGZO) oxide semiconductor TFTs have attracted much interest due to its high mobility, optical transparency, and large area uniformity. However, due to the intrinsic problem of a-IGZO TFTs caused by oxygen vacancy and hydrogen, it is hard to control of threshold voltage (Vth) and stability under various stress conditions. One of them, hydrogen is the main factor closely related to reliability. According to previous studies, hydrogen acts as positive roles by defect passivation and also play negative roles in creating new defects in a-IGZO active layer. However, incorporation and diffusion of hydrogen into the active layer is an unavoidable issue during the TFTs fabrication, and it is important to control it so that hydrogen plays a positive role. So, in this study, we conducted experiments to verify the effect of hydrogen on the reliability by modifying the Al2O3 gate insulator layer (GI) deposition process using atomic layer deposition (ALD) method. In order to verify the relationship between the hydrogen and electrical properties of a-IGZO TFTs, we fabricated top gate bottom contact (TGBC) structures and applied different GI deposition temperature (Tdep) for controlling the amount of hydrogen. [1] Al2O3 GI deposited using trimethylaluminum (TMA) and H2O precursor. Each Tdep are 200, 250, 270 and 300 degree, respectively. As a result of Al2O3 single thin film analysis using secondary ion mass spectroscopy (SIMS) method, it was confirmed that the Al2O3 thin film deposited at high Tdep has a relatively small amount of hydrogen than the Al2O3 thin film deposited at low Tdep. And then, TFT devices a, b, c, and d were fabricated using Al2O3 GI with different Tdep of 200, 250, 270 and 300 degrees, respectively. As a result, there was no significant difference between the devices. All devices had subthreshold swing (SS), value of 0.178 ~ 0.225 V, turn on voltage (Von) of -0.16 ~ -0.44V, hysteresis of 0.13 ~ 0.27 V and field effect mobility (μFE) of 9.6 ~ 10.55 cm2/Vs. This trend was similar to positive bias temperature stress (PBTS) and negative bias temperature stress (NBTS) reliability. However, the reliability of negative bias illumination stress (NBIS) was significantly different for each device. Under the NBIS condition, the Vth shift of each TFT was -4.36 V for a TFT, -4.36 V for b TFT, -3.72V for c TFT, -2.48 V for d TFT. These results indicate that the NBIS characteristic is improved as the Tdep of Al2O3 GI increases and proves that reliability varies with the amount of hydrogen. This suggests that as hydrogen increases, more hydrogen-induced defects are formed at the interface between GI and a-IGZO active layer, which causes trapping of positive charges. This phenomenon can be explained by non-bridging oxygen hole center (NBOHC) method, which is one of the positive charge trapping models, and the mechanism for the role of hydrogen in the a-IGZO TFTs can be identified. [2] Base on these experimental results, we will propose the way to optimize condition of GI deposition process for high stability and high performance in a-IGZO TFTs. [1] S.J. Yun, K.-H. Lee, J. Skarp, H.-R. Kim and K.-S. Nam, J. Vac. Sci. Technol. A, 15(6) (1997) [2] M. Tsubuku, R. Watanabe, N. Ishihara, H. Kishida, M. Takahashi, S. Yamazaki, Y. Kanzaki, H. Matsukizono, S. Mori, T. Matsue, SID 2013 DIGEST. 169 (2013)