• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.7
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• pp.494-498
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• 2003

In this paper, the plasma treatment on gate surface has been applied prior to deposition of pentacene and the effects on performance were investigated. The Plasma treatment produced the mobility of 0.05$\textrm{cm}^2$/V.sec which is 10 times larger than the non-treated. The resistance was also reduced from 400K$\Omega$ to 50K$\Omega$. In addition, the standard deviation of performance parameters variation was reduced with the plasma exposure time, which implies that plasma treatment makes the gate surface states be uniform across the whole wafer area. The performance parameters were increased with the exposure time up to 5min, after which they degraded again. Therefore, the optimal exposure time was found to be 5min.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.95-96
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• 2008

A new voltage-driven pixel circuit using soluble-processed organic thin film transistors (OTFTs) for an active matrix organic light emitting diode (AMOLED) is proposed. The proposed circuit is composed of four switching TFTs, one driving TFT and one storage capacitor. The proposed circuit can compensate for the degradation of OLED current caused by the threshold voltage shift of the OTFT. The simulation results show that the variation of OLED current corresponding to a 3V threshold voltage shift is decreased by 30% compared to the conventional 2TlC structure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.182-183
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• 2008

We fabricated a pentacene thin film transistor with Poly-vinylalcohol (PVA) as a dielectric. And we used Poly(9-vinylcarbazole) (PVK) as a buffer layer to improve the electrical characteristics. PVK is a material used often host material for OLED device, as it has good film forming properties, large HOMO-LUMO(highest occupied molecular orbital-lowest unoccupied molecular orbital) bandgap. The performance of a OTFT device with PVA gate dielectric was improved by using the PVK. Field effect mobility, threshold voltage, and on-off current ratio of device with PVK layer were about 0.6 $cm^2$/Vs, -17V, and $5\times10^5$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.61-62
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• 2006

In this paper, it was demonstrated that organic thin- film transistors (OTFTs) were fabricated with the organic adhesion layer between an organic semiconductor and a gate insulator by vapor deposition polymerization (VDP) processing. In order to form polymeric film as an adhesion layer, VDP process was also introduced instead of spin-coating process, where polymeric film was co-deposited by high-vacuum thermal evaporation from 6FDA and ODA followed by curing. The saturated slop in the saturation region and the subthreshold nonlinearity in the triode region were c1early observed in the electrical output characteristics in our organic thin film transistors using the staggered-inverted top-contact structure. Field effect mobility, threshold voltage, and on-off current ratio in 15-nm-thick organic adhesion layer were about $0.5\;cm^2/Vs$, -1 V, and $10^6$, respectively. We also demonstrated that threshold voltage depends strongly on the delay time when a gate voltage has been applied to bias stress.

• Journal of the Korean Applied Science and Technology
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• v.16 no.4
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• pp.313-316
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• 1999

Organic semiconductors based on conjugated thiophene oligomer have great potential to be utilized as an active layer for electronic and optoelectronic devices. In this study, a conjugated oligomer such as ${\alpha}$-sexithiophene (${\alpha}$-6T) thin films was prepared by the Organic Molecular Beam Deposition (OMBD), and various electrode materials were also deposited by a simple vacuum evaporation, respectively. Those films were photolithographically patterned for the electrical measurements. Electrical charact-erization of the thin film transistor with various channel length were executed and the field effect mobility of these thin film transistors were also calculated by the formula using the experimental data.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.418-419
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• 2013

현재, 인듐 주석 산화물(indium tin oxide, ITO) 박막은 가시영역에서 전기적 특성 및 광학적 특성이 우수하기 때문에 평면 디스플레이(flat displays), 박막 트랜지스터(thin film transistors), 태양전지(solar cells) 등을 포함한 광소자에 투명전도성산화물(transparent conducting oxide, TCO) 전극으로 가장 일반적으로 사용되고 있다. 하지만, 이 물질은 밴드갭이 3.4 eV로 다소 작아 다양한 분야의 의료기기, 환경 보호에 응용 가능한 자외선 영역에서 상당히 많은 양의 광흡수가 발생하는 치명적인 문제점을 가지고 있다. 또한, 인듐(Indium)의 급속한 소비는 인듐의 매장량의 한계로 인해 가격을 상승시키는 주요한 원인으로 작용하고 있다. 한편, InGaN 기반의 자외선 발광다이오드 분야에서는 팔라듐(Pd) 기반의 반투명 전극과 은(Ag) 기반의 반사전극을 주로 사용하고 있지만, 낮은 투과도와 낮은 굴절률을 때문에 여전히 자외선 발광다이오드의 광추출 효율(extraction efficiency)에 문제점을 가지고 있다. 따라서 자외선 발광다이오드의 외부양자 효율(external quantum efficiency, EQE)을 높이기 위해 높은 투과도와 GaN와 유사한 굴절률을 가지는 p-형 오믹 전극을 개발해야 한다. 본 연구에서는 초박막의 ITO (16 nm)/Ag (7 nm)/ITO (16 nm) 다층 구조를 갖는 투명전도성 전극을 제작한 후, 열처리 온도에 따른 전기, 광학적 특성에 향상에 대해서 조사하였다. 사용된 산화물/금속/산화물 전극의 구조는 유기발광 다이오드(organic light emitting diode, OLED), 태양전지 등에 많이 사용되는 안정적인 투명 전극을 자외선 LED 소자에 처음 적용하여, ITO의 전체 사용량은 줄이고, ITO 사이에 금속을 삽임함으로써 금속에 의한 전기적 특성 향상과 플라즈몬 효과에 의한 투과도를 높일 수 있는 장점을 가지고 있다. 실험 결과로는, $400^{\circ}C$에서 열처리한 ITO/Ag/ITO 다층 구조는 365 nm에서 84%의 광학적 특성과 9.644 omh/sq의 전기적 특성을 확인하였다. 실험 결과로부터 좀 더 최적화를 수행하면, ITO/Ag/ITO 다층 구조는 자외선 발광다이오드의 투명전도성 전극으로 사용될 수 있을 것이라 기대된다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.6
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• pp.588-593
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• 2023

The advantage of OTFT technology is that large-area circuits can be manufactured on flexible substrates using a low-cost solution process such as inkjet printing. Compared to silicon-based inorganic semiconductor processes, the process temperature is lower and the process time is shorter, so it can be widely applied to fields that do not require high electron mobility. Materials that have utility as electrode materials include carbon that can be solution-processed, transparent carbon thin films, and metallic nanoparticles, etc. are being studied. Recently, a technology has been developed to facilitate charge injection by coating the surface of the Al electrode with solution-processable titanium oxide (TiOx), which can greatly improve the performance of OTFT. In order to commercialize OTFT technology, an appropriate method is to use a complementary circuit with excellent reliability and stability. For this, insulators and channel semiconductors using organic materials must have stability in the air. In this study, carbon-doped Mo (MoC) thin films were fabricated with different graphite target power densities via unbalanced magnetron sputtering (UBM). The influence of graphite target power density on the structural, surface area, physical, and electrical properties of MoC films was investigated. MoC thin films deposited by the unbalanced magnetron sputtering method exhibited a smooth and uniform surface. However, as the graphite target power density increased, the rms surface roughness of the MoC film increased, and the hardness and elastic modulus of the MoC thin film increased. Additionally, as the graphite target power density increased, the resistivity value of the MoC film increased. In the performance of an organic thin film transistor using a MoC gate electrode, the carrier mobility, threshold voltage, and drain current on/off ratio (I_on/I_off) showed 0.15 cm²/V·s, -5.6 V, and 7.5×10⁴, respectively.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1313-1314
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• 2007

This paper presents organic thin-film transistors (OTFTs) with poly(3-hexylthiophene)(P3HT) semiconductor and several polymeric dielectric materials of poly(vinyl phenol)(PVP), poly(vinyl alcohol)(PVA), and polyimide(PI) by using soluble process. The fabricated OTFT's have inverted staggered structure using transmission line method(TLM) pattern. In order to evaluate the electrical characteristics of the OTFT, capacitance-voltage(C-V) and current-voltage(I-V) were measured. C-V graphs were measured at several frequencies of 100 Hz, 1 kHz, and 1 MHz and ID-VDS graphs according to $V_{GS}$. The current on/off ratio and threshold voltage with each of PVP, PVA, and PI based OTFTs were measured to $10^3$, and -0.36, -0.41, and -0.62 V. Also, the calculated mobility with each of PVP, PVA, and PI was 0.097, 0.095, and 0.028 $cm^{2}V^{-1}s^{-1}$, respectively. In the cases of PVP and PVA, the hole mobility of P3HT was in excellent agreement with the published value of 0.1 $cm^{2}V^{-1}s^{-1}$.

• Advanced Industrial SCIence
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• v.1 no.1
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• pp.16-22
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• 2022

Starting with cathode ray tubes, displays are forming markets in the order of active marix organic light emitting diode (AMOLED) after PDP (Plasma Display Panel) and LCD (Liquid Crystal Display). OLED is recognized as a key field for the development of each country preparing for the fourth industrial revolution, and especially Samsung Display and LG Display, which are the top industries in Korea, are leading the market with more than 90% of OLED shares. Currently, AMOLED has moved to the area that can be folded or bent. This technology is possible because TFT (Thin Film Transistor) and OLED may be formed on a flexible substrate. In the future, the technology will move to stretchable displays, and for this, the development of substrate materials is first, and then TFT and OLED devices should also be implemented with stretchable materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05a
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• pp.177-180
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• 2004

In this study, we report a novel encapsulation method for longevity of an organic thin-film transistor (OTFT) using pentaceneby means of an adhesive multiplayerincluded Al film. For encapsulation of OTFTs, the Al film adhered onto the OTFT in a dry nitrogen atmosphere using a proper adhesive. A lifetime, which was defined as the time necessary to reduce mobility to 2% of initial mobility value, was observed from the typical $I_{D-VD}$ characteristics of the field-effect transistor (FET). The initial field effect mobility ${\mu}$ was measured to be $2.0{\times}10^{-1}\;cm^2/Vs$. The characterization was maintained for long times in air. No substantial degeneration occurred. The performance and the stability are probably due to the encapsulation effect.