• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.491-491
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• 2011

Transparent and flexible electronic devices that are light-weight, unbreakable, low power consumption, optically transparent, and mechanical flexible possibly have great potential in new applications of digital gadgets. Potential applications include transparent displays, heads-up display, sensor, and artificial skin. Recent reports on transparent and flexible field-effect transistors (tf-FETs) have focused on improving mechanical properties, optical transmittance, and performances. Most of tf-FET devices were fabricated with transparent oxide semiconductors which mechanical flexibility is limited. And, there have been no reports of transparent and flexible all-organic tf-FETs fabricated with organic semiconductor channel, gate dielectric, gate electrode, source/drain electrode, and encapsulation for sensor applications. We present the first demonstration of transparent, flexible all-organic sensor based on multifunctional organic FETs with organic semiconductor channel, gate dielectric, and electrodes having a capability of sensing infrared (IR) radiation and mechanical strain. The key component of our device design is to integrate the poly(vinylidene fluoride-triflouroethylene) (P(VDF-TrFE) co-polymer directly into transparent and flexible OFETs as a multi-functional dielectric layer, which has both piezoelectric and pyroelectric properties. The P(VDF-TrFE) co-polumer gate dielectric has a high sensitivity to the wavelength regime over 800 nm. In particular, wavelength variations of P(VDF-TrFE) molecules coincide with wavelength range of IR radiation from human body (7000 nm ~14000 nm) so that the devices are highly sensitive with IR radiation of human body. Devices were examined by measuring IR light response at different powers. After that, we continued to measure IR response under various bending radius. AC (alternating current) gate biasing method was used to separate the response of direct pyroelectric gate dielectric and other electrical parameters such as mobility, capacitance, and contact resistance. Experiment results demonstrate that the tf-OTFT with high sensitivity to IR radiation can be applied for IR sensors.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2007.06a
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• pp.124-124
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• 2007

• Journal of the Semiconductor & Display Technology
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• v.11 no.1
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• pp.29-33
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• 2012

In this study, we have investigated the structural and electrical characteristics of IZO thin films deposited under hydrogen atmosphere on flexible substrate for the OLED (organic light emitting diodes) devices. For this purpose, PES was used for flexible substrate and IZO thin films were deposited by RF magnetron sputtering under hydrogen ambient gases (Ar, $Ar+H^2$) at room temperature. In order to investigate the influences of the hydrogen, the flow rate of hydrogen in argon mixing gas has been changed from 0.1sccm to 0.5sccm. All the samples show amorphous structure regardless of flow rate. The electrical resistivity of IZO films increased with increasing flow rate of $H^2$ under $Ar+H^2$. All the films showed the average transmittance over 85% in the visible range. The OLED device was fabricated with different IZO electrodes made by configuration of IZO/$\acute{a}$-NPD/DPVB/$Alq_3$/LiF/Al to elucidate the performance of IZO substrate. OLED devices with the amorphous-IZO (a-IZO) anode film show good current density-voltage-luminance characteristics. This suggests that flat surface roughness and low electrical resistivity of a-IZO anode film lead to more efficient anode material in OLED devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.5
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• pp.531-535
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• 2023

Mechanoluminescence (ML) is a phenomenon where the application of mechanical force to ML materials generates an electric field and produces light, holding significant promise as an eco-friendly technology. However, challenges in commercializing ML technology has arisen due to its low brightness and short luminous lifetime. To address this, in this work, we enhance ML efficiency by mixing carbon nanotubes (CNTs) into a ZnS: Cu embedded in a polydimethylsiloxane composite ML device. The inclusion of CNTs boosts ML intensity by 98% compared to devices without CNTs, as the increasing CNT fraction elevates conductivity, thereby amplifying ML intensity. However, this increase in CNT fraction also leads to enhanced light absorption within the device. Consequently, we observe a trend where ML intensity rises initially but declines beyond a CNT fraction of 0.0015 wt%. Based on these findings, we anticipate that our research will make valuable contributions to the advancement of electrical powerless mechanoluminescent technology.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.154-154
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• 2012

Flexible complementary inverters based on thin-film transistors (TFTs) are important because they have low power consumption and high voltage gain compared to single type circuits. We have manufactured flexible complementary inverters using pentacene and amorphous indium gallium zinc oxide (IGZO) for the p-channel and n-channel, respectively. The circuits were fabricated on polyimide (PI) substrate. Firstly, a thin poly-4-vinyl phenol (PVP) layer was spin coated on PI substrate to make a smooth surface with rms surface roughness of 0.3 nm, which was required to grow high quality IGZO layers. Then, Ni gate electrode was deposited on the PVP layer by e-beam evaporator. 400-nm-thick PVP and 20-nm-thick ALD Al2O3 dielectric was deposited in sequence as a double gate dielectric layer for high flexibility and low leakage current. Then, IGZO and pentacene semiconductor layers were deposited by rf sputter and thermal evaporator, respectively, using shadow masks. Finally, Al and Au source/drain electrodes of 70 nm were respectively deposited on each semiconductor layer using shadow masks by thermal evaporator. The characteristics of TFTs and inverters were evaluated at different bending radii. The applied strain led to change in voltage transfer characteristics of complementary inverters as well as source-drain saturation current, field effect mobility and threshold voltage of TFTs. The switching threshold voltage of fabricated inverters was decreased with increasing bending radius, which is related to change in parameters of TFTs. Throughout the bending experiments, relationship between circuit performance and TFT characteristics under mechanical deformation could be elucidated.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.171-176
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• 2021

Die-to-wafer (D2W) hybrid bonding in the multilayer semiconductor manufacturing process is one of wafer direct bonding, and various studies are being conducted around the world. A noteworthy point in the current die-to-wafer process is that a lot of voids occur on the bonding surface of the die during bonding. In this study, as a suggested method for removing voids generated during the D2W hybrid bonding process, a flexible mechanism for implementing convex for die bonding to be applied to the bond head is proposed. In addition, modeling of flexible mechanisms, analysis/design/control/evaluation of static/dynamics properties are performed. The proposed system was controlled by capacitive sensor (lion precision, CPL 290), piezo actuator (P-888,91), and dSpace. This flexure mechanism implemented a working range of 200 ㎛, resolution(3σ) of 7.276nm, Inposition(3σ) of 3.503nm, settling time(2%) of 500.133ms by applying a reverse bridge type mechanism and leaf spring guide, and at the same time realized a maximum step difference of 6 ㎛ between die edge and center. The results of this study are applied to the D2W hybrid bonding process and are expected to bring about an effect of increasing semiconductor yield through void removal. In addition, it is expected that it can be utilized as a system that meets the convex variable amount required for each device by adjusting the elongation amount of the piezo actuator coupled to the flexible mechanism in a precise unit.

• Proceedings of the Korean Vacuum Society Conference
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• 2008.08a
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• pp.337-337
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• 2008

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.1
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• pp.87-96
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• 2019

Flexible organic light-emitting diode (OLED) displays with organic thin-film transistors (OTFTs) backplanes have been studied. A gate driver is required to drive the OLED display. The gate driver is integrated into the panel to reduce the manufacturing cost of the display panel and to simplify the module structure using fabrication methods based on low-temperature, low-cost, and large-area printing processes. In this paper, pseudo complementary metal oxide semiconductor (CMOS) logic gates are implemented using OTFTs for the gate driver integrated in the flexible OLED display. The pseudo CMOS inverter and NAND gates are designed and fabricated on a flexible plastic substrate using inkjet-printed OTFTs and the same process as the display. Moreover, the operation of the logic gates is confirmed by measurement. The measurement results show that the pseudo CMOS inverter can operate at input signal frequencies up to 1 kHz, indicating the possibility of the gate driver being integrated in the flexible OLED display.

• Journal of IKEEE
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• v.27 no.4
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• pp.668-678
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• 2023

FlexRay is an in-vehicle network with maximum two channels and maximum transmission speed of 10Mbps per channel. FlexRay exploits TDMA (Time Division Multiple Access) and FTDMA (Flexible Time division Multiple Access) to ensure real-time communication with efficient transmission, so it is used for real-time electronic control of safety-critical vehicular modules such as powertrain. This paper explains FlexRay protocol, time hierarchy, message frame, communication controller, and conformance test in detail based on ISO 17458 standard and FlexRay consortium documents.

• Vacuum Magazine
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• v.1 no.2
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• pp.24-29
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• 2014

Display is a key component in electronic devices. OLED is growing very fast recently due to the explosion of the smart phone market although still LCD is the dominating display technology in the display market at the moment. Also needs for the large area and high resolution TVs and flexible displays are increasing these days. Especially flexible display is expected to be one of the key technologies in mobile devices requiring small device size and large display size. Contrary to the conventional displays, flexible display requires organic materials for the substrate, the active driving element and also for the display element. Plastic film as a substrate, organic semiconductor as an active component of the transistor and organic light emitting materials or electronic paper as a display element are studied actively. In this article, mainly backplane technologies such as substrates and the transistor materials for flexible display will be introduced.