• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.543-545
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• 2009

With injection-type source delivery system of atomic layer deposition (ALD), bottom-contact and bottom-gate thin-film transistors (TFTs) were fabricated with a poly-4-vinyphenol polymeric dielectric for the first time. The properties of the ZnO TFT were greatly influenced by the device structure and the process conditions. The zinc oxide TFTs exhibited a channel mobility of 0.43 $cm^2$/Vs, a threshold voltage of 0.85 V, a subthreshold slope of 3.30 V/dec, and an on-to-off current ratio of above $10^6$ with solid saturation.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.64.1-64.1
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• 2012

Next generation displays such as high performance LCD, AMOLED, flexible display and transparent display require specific TFT back-planes. For high performance TFT back-planes, low temperature poly silicon (LTPS), and metal-oxide semiconductors are studied. Flexible TFT backplanes require low temperature processible organic semiconductors. Not only development of active semiconducting materials but also design and synthesis of semiconductor corresponding gate dielectric materials are important issues in those display back-planes. In this study, we investigate the high heat resistant polymeric gate dielectric materials for organic TFT and inorganic TFT with good insulating properties and processing chemical resistance. We also controlled and optimized surface energy and morphology of gate dielectric layers for direct printing process with solution processible organic and inorganic semiconductors.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1305-1307
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• 2009

We have investigated the new modification of poly (vinyl phenol) (PVP) for low hysteresis organic thin film transistors (OTFTs). In order to suppression of hysteresis phenomenon, synthesized various backbone structure polymeric gate dielectric. The modified polymeric dielectric was synthesized by inducing ringshape phenol backbone structure instead of conventional chain. We could be observed that relieved hysteresis and excellent air stability from ring-shape phenol backbone structure.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.168-168
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• 2006

Low-operating voltage organic field-effect transistors (OFETs) have been realized with high dielectric constant (${\kappa}$) polymer such as cyanoethylated poly vinyl alcohol (CR-V, ${\kappa}=12$). Since the $high-{\kappa}$polymers are likely to contain water and ionic impurities, large hysteresis and considerable leakage current are frequently observed in OFETs. To solve these problems, we cross-linked the CR-V by using a cross-linking agent. Cross-linked CR-V dielectrics showed high dielectric constant of 11.1 and good insulating properties, resulting in a high capacitance ($81nF/cm^{2}$ at 1MHz) at 120 nm of dielectric thickness. Pentacene FETs with cross-linked CR-V dielectrics exhibited high carrier mobility ($0.72\;cm^{2}/Vs$), small subthreshold swing (185 mV/dec) and little hysteresis at low-operating voltage (${\Leq}-3V$).

• Journal of Information Display
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• v.4 no.2
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• pp.1-6
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• 2003

In this paper, we demonstrate that the organic electrophosphorescent device is driven by the organic thin film transistor with spin-coated photoacryl gate insulator. It was found that electrical output characteristics in our organic thin film transistors using the staggered-inverted top-contact structure showed the non-saturated slope in the saturation region and the sub-threshold nonlinearity in the triode region, where we obtained the maximum power luminance that was about 90 $cd/m^2$. Field effect mobility, threshold voltage, and on-off current ratio in 0.45 ${\mu}m$ thick gate dielectric layer were 0.17 $cm^2/Vs$, -7 V, and $10^6$ , respectively. In order to form polyimide as a gate insulator, vapor deposition polymerization process was also introduced instead of spin-coating process, where polyimide film was co-deposited by high-vacuum thermal evaporation from 4,4'-oxydiphthalic anhydride (ODPA) and 4,4'-oxydianiline (ODA) and cured at 150${\sqsubset}$for 1hr. It was also found that field effect mobility, threshold voltage, on-off current ratio, and sub-threshold slope with 0.45 ${\mu}m$ thick gate dielectric films were 0.134 $cm^2/Vs$, -7 V, and $10^6$ A/A, and 1 V/decade, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1348-1351
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• 2007

We demonstrated that the threshold voltage shift owing to a gate-bias stress is originated from the trapped charges at the interface between semiconductor layer and dielectric layer, and such drawback can be settled by applying long-term delay time to the gate electrode.

• Journal of Adhesion and Interface
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• v.22 no.3
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• pp.91-97
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• 2021

By introducing an organic interlayer on the Parylene C dielectric surface, the electrical device performances and the operating stabilities of organic field-effect transistors (OFETs) were improved. To achieve this goal, hexamethyldisilazane (HMDS) and octadecyltrichlorosilane (ODTS), as the organic interlayer materials, were used to control the surface energy of the Parylene C dielectrics. For the bare case used with the pristine Parylene C dielectrics, the field-effect mobility (μ_FET) and threshold voltage (V_th) of dinaphtho[2,3-b:2',3'-f ]thieno[3,2-b]- thiophene (DNTT) FET devices were measured at 0.12 cm²V^-1s^-1 and - 5.23 V, respectively. On the other hand, the OFET devices with HMDS- and ODTS-modified cases showed the improved μ_FET values of 0.32 and 0.34 cm²V^-1s^-1, respectively. More important point is that the μ_FET and V_th of the DNTT FET device with the ODTS-modified Parylene C dielectric presented the smallest changes during a repeated measurement of 1000 times, implying that it has the most stable operating stability. The results could be meaned that the organic interlayer, especially ODTS, effectively covers the Parylene C dielectric surface with alkyl chains and reduces the charge trapping at the interface region between active layer and dielectric, thereby improving the electrical operating stability.

• 전자공학회논문지 IE
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• v.43 no.1
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• pp.1-4
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• 2006

The characteristics of polymeric thin-film transistors(TFTs) can be controlled by chemically modifying the surface of the gate dielectric prior to the organic semiconductor. The chemical treatment consists of derivative the tantalum pentoxide($Ta_2O_5$) surface with organic materials to form self-assembled monolayer(SAM). The deposition of an octadecyl-trichlorosilane(OTS), hexamethy-ldisilazone(HMDS), aminopropyltreithoxysilane(ATS) SAM leads to a mobility of $0.01\sim0.06cm2/V{\cdot}s$ in a poly-3-hexylthiophene(P3HT) conjugated polymer. The mobility enhancement mechanism is likely to involve molecular interactions between the polymer and SAM. These result can be used for polymer TFT's dielectric material.

• Journal of the Korean Applied Science and Technology
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• v.29 no.2
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• pp.199-204
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• 2012

Organic thin-film transistors (OTFTs) have received considerable attention because their potential applications for nano-scale thin-film structures have been widely researched for large-scale integration industries, such as semiconductors and displays. However, research in developing n-type materials and devices has been relatively shortage than developing p-type materials. Therefore, we report on the fabrication of top-contact [6,6]-phenyl-C61-butyricacidmethylester (PCBM) TFTs by using three different solvent, o-dichlorobenzene, toluene and chloroform. An appropriate choice of solvent shows that the electrical characteristics of PCBM TFTs can be improved. Moreover, our PCBM TFTs with the cross-linked Poly(4-vinylphenol) dielectric layer exhibits the most pronounced improvements in terms of the field-effect mobility (${\sim}0.034cm^2/Vs$) and the on/off current ratio (${\sim}1.3{\times}10^5$) for our results. From these results, it can be concluded that solvent-modification of an organic semiconductor in PCBM TFTs is useful and can be extended to further investigations on the PCBM TFTs having polymeric gate dielectrics. It is expected that process optimizations using solution-processing of organic semiconductor materials will allow the development of the n-type organic TFTs for low-cost electronics and various electronic applications.