• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.571-574
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• 2009

Metal oxide/metal bilayer structures are explored as contacts with a low injection barrier in organic thin-film transistors (OTFTs) in an effort to realize their true potential for low-cost electronics. OTFTs with a bilayer electrode of $WO_3$ (10nm) and Al shows a saturation mobility as large as 0.97 $cm^2$/Vsec which are comparable to those of Au-based control samples (~0.90 $cm^2$/Vsec). Scaling of contact resistance with respect to the thickness of $WO_3$ layer is also discussed.

• 한국전기전자재료학회논문지
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• 제28권6호
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• pp.351-359
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• 2015

Next-generation displays should be transparent and flexible as well as having high resolution and frame number. The main factor for active matrix organic light emitting diode and next-generation displays is the development of TFTs (thin-film transistors) with high mobility and large area uniformity. The TFTs used for transparent displays are mainly oxide TFT that has oxide semiconductor as channel layer. Zinc-oxide based substances such as indium-gallium-zinc-oxide has attracted attention in the display industry. In this paper, the mobility improvement of low cost oxide TFT is studied for fast operating next-generation displays by overcoming disadvantages of amorphous silicon TFT that has low mobility and poly silicon TFT that requires expensive equipment for complex process and doping process.

• 한국재료학회지
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• 제20권8호
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• pp.401-407
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• 2010

We studied the influence of different types of metal electrodes on the performance of solution-processed zinc tin oxide (ZTO) thin-film transistors. The ZTO thin-film was obtained by spin-coating the sol-gel solution made from zinc acetate and tin acetate dissolved in 2-methoxyethanol. Various metals, Al, Au, Ag and Cu, were used to make contacts with the solution-deposited ZTO layers by selective deposition through a metal shadow mask. Contact resistance between the metal electrode and the semiconductor was obtained by a transmission line method (TLM). The device based on an Al electrode exhibited superior performance as compared to those based on other metals. Kelvin probe force microscopy (KPFM) allowed us to measure the work function of the oxide semiconductor to understand the variation of the device performance as a function of the types metal electrode. The solution-processed ZTO contained nanopores that resulted from the burnout of the organic species during the annealing. This different surface structure associated with the solution-processed ZTO gave a rise to a different work function value as compared to the vacuum-deposited counterpart. More oxygen could be adsorbed on the nanoporous solution-processed ZTO with large accessible surface areas, which increased its work function. This observation explained why the solution-processed ZTO makes an ohmic contact with the Al electrode.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.222-222
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• 2010

Transparent semiconductor oxide thin films have been attracting considerable attention as potential channel layers in thin film transistors (TFTs) owing to their several advantageous electrical and optical characteristics such as high mobility, high stability, and transparency. TFTs with ZnO or similar metal oxide semiconductor thin films as the active layer have already been developed for use in active matrix organic light emitting diode (AMOLED). Of late, there have been several reports on TFTs fabricated with InZnO, AlZnSnO, InGaZnO, or other metal oxide semiconductor thin films as the active channel layer. These newly developed TFTs were expected to have better electrical characteristics than ZnO TFTs. In fact, results of these investigations have shown that TFTs with the new multi-component material have excellent electrical properties. In this work, we present TFTs with inverted coplanar geometry and with a novel HfInZnO active layer co-sputtered at room temperature. These TFTs are meant for use in low voltage, battery-operated mobile and flexible devices. Overall, the TFTs showed good performance: the low sub-threshold swing was low and the $I_{on/off}$ ratio was high.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.48.1-48.1
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• 2009

Performance of organic field-effect transistors (OFETs) with various temperature-cured polyacrylate(PA) copolymer as a gate insulator was studied. The PA thin film, which was cured at an optimized temperature, showed high dielectric strength (>7 MV/cm), low leakage current density ($5{\times}10^{-9}\;A/cm^2$ at 1 MV/cm) and enabled negligible hysteresis in MIS capacitor and OFET. A field-effect mobility of ${\sim}0.6\;cm^2/V\;s$, on/off current ratio (Ion/Ioff) of ${\sim}10^5$ and inverse subthreshold slope (SS) as low as 1.22 V/decwere achieved. The high dielectric strength made it possible to scale down the thickness of dielectric, and low-voltage operation of -5 V was successfully realized. The chemical changes were monitored by FT-IR. The morphology and microstructure of the pentacene layer grown on PA dielectrics were also investigated and correlated with OFET device performance.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.176-176
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• 2010

One of the critical issues for applications of flexible organic thin film transistors (OTFTs) for flexible electronic systems is the electrical stabilities of the OTFT devices, including variation of the current on/off ratio (Ion/Ioff), leakage current, threshold voltage, and hysteresis under repetitive mechanical deformation. In particular, repetitive mechanical deformation accelerates the degradation of device performance at the ambient environment. In this work, electrical stability of the pentacene organic thin film transistors (OTFTs) employing multi-stack hybrid encapsulation layers was investigated under mechanical cyclic bending. Flexible bottom-gated pentacene-based OTFTs fabricated on flexible polyimide substrate with poly-4-vinyl phenol (PVP) dielectric as a gate dielectric were encapsulated by the plasma-deposited organic layer and atomic-layer-deposited inorganic layer. For cyclic bending experiment of flexible OTFTs, the devices were cyclically bent up to 105 times with 5mm bending radius. In the most of the devices after 105 times of bending cycles, the off-current of the OTFT with no encapsulation layers was quickly increased due to increases in the conductivity of the pentacene caused by doping effects from $O_2$ and $H_2O$ in the atmosphere, which leads to decrease in the Ion/Ioff and increase in the hysteresis. With encapsulation layers, however, the electrical stabilities of the OTFTs were improved significantly. In particular, the OTFTs with multi-stack hybrid encapsulation layer showed the best electrical stabilities up to the bending cycles of $10^5$ times compared to the devices with single organic encapsulation layer. Changes in electrical properties of cyclically bent OTFTs with encapsulation layers will be discussed in detail.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.9-10
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• 2006

The patterning for the active layer of organic semiconductors is important to attain completely organic-based OTFTs(Organic Thin Film Transistors). We studied on possibility of the application of the conventional photolithography technique to pattern the organic active layer poly(3-hexylthiophene)(P3HT). Patterned P3HT-based OTFTs with Bottom Contact(BC) configuration were fabricated using the conventional photolithography. We achieved field-effect mobilities in the saturation regime ${\sim}1.2{\times}10^{-3}cm^2/V{\cdot}s$, $I_{on/off}$ ratios ${\sim}10^5$ in the subtractive method, ${\sim}8{\times}10^{-4}cm^2/V{\cdot}s$, $I_{on/off}$ ratios ${\sim}10^3$ in the additive one.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.170-170
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• 2006

[ ${\pi}-conjugated$ ] organic and polymeric semiconductors are receiving considerable attention because of their suitability as an active layer for electronic devices. An organic inverter with a full swing and a high gain can be obtained through the good qualities of the transfer characteristics of organic thin-film transistors (OTFTs); for example, a low leakage current, a threshold voltage ($V_{th}$) close to 0 V, and a low sub-threshold swing. One of the most critical problems with traditional organic inverters is the high operating voltage, which is often greater than 20 V. The high operating voltage may result in not only high power consumption but also device instabilities such as hysteresis and a shift of $V_{th}$ during operation. In this paper, low-voltage and little-hysteresis pentacene OTFTs and inverters in conjunction with PEALD $Al_{2}O_{3}\;and\;ZrO_{2}$ as the gate dielectrics are demonstrated and the relationships between the transfer characteristics of OTFT and the voltage transfer characteristics (VTCs) of inverter are investigated.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1424-1427
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• 2005

In this paper, we studied on the application of Organic Thin Film Transistors (OTFTs) to the active matrix organic light emitting diodes (AMOLED). We designed organic transistor based pixel circuits for AMOLED. The pixel circuit is consisted of two-transistor, one-capacitor and one-OLED. We report the simulation results of the pixel circuits that OLED current varied as the data line and scan line voltage. Also, we will describe the fabrication process of the Pentacene OTFTs arrays and the organic light emitting diodes. The driving results of the fabricated unit pixels and their 4x4 arrays are also presented.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.56-56
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• 2010

We report a low-temperature fabrication of organic/inorganic nanohybrid dielectrics for organic thin film transistors. The self-assembled organic layers (SAOLs) were grown by repeated sequential adsorptions of C=C-terminated alkylsilane and metal (Al or Ti) hydroxyl with ozone activation, which was called "molecular layer deposition (MLD)". The $TiO_2$ and $Al_2O_3$ inorganic layers were grown by ALD, which relies on sequential saturated surface reactions resulting in the formation of a monolayer in each sequence and is a potentially powerful method for preparing high quality multicomponent superlattices. The MLD method combined with ALD (MLD-ALD) was applied to fabricate SAOLs-$Al_2O_3$-SAOLs-$TiO_2$ nanohybrid superlattices on polymer substrates at relatively low temperature. The MLD method is an ideal fabrication technique for various flexible electronic devices.