• Macromolecular Research
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• v.17 no.6
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• pp.436-440
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• 2009

We improved the performance of pentacene-based thin film transistors by changing the curing environment of poly(4-vinylphenol) (PVP) gate dielectrics, while keeping the dielectric constant the same. The field-effect mobility of the pentacene TFTs constructed using the vacuum cured PVP was higher than that of the device based on the Ar flow cured gate dielectric, possibly due to the higher crystalline perfection of the pentacene films. The present results demonstrated that the curing conditions used can markedly affect the surface energy of polymer gate dielectrics, thereby affecting the field-effect mobility of TFTs based on those dielectrics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.12
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• pp.759-763
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• 2016

We demonstrate the utilization of ion gel gate dielectrics for operating non-volatile transistor memory devices based on polymer semiconductor thin films. The gating process in typical electrolyte-gated polymer transistors occurs upon the penetration and escape of ionic components into the active channel layer, which dopes and dedopes the polymer film, respectively. Therefore, by controlling doping and dedoping processes, electrical current signals through the polymer film can be memorized and erased over a period of time, which constitutes the transistor-type memory devices. It was found that increasing the thickness of polymer films can enhance the memory performance of device including (i) the current signal ratio between its memorized state and erased state and (ii) the retention time of the signal.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1353_1354
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• 2009

The OTFT devices had inverted staggered structures of Au/pentacene/ppMMA/ITO on PET substrate. The overall device performances of the flexible devices such as the operating voltage, the field effect mobility, the on/off ratio and the off current are somewhat worse than those of devices fabricated on glass substrates. Pentacene/ppMMA OTFT benchmarks (mobility, sub-threshold slope, on/off ratio) were comparable to that of solution cast PMMA, but below average when compared to other polymer gate dielectrics. However, threshold and drive voltages were among the lowest reported for a polymer gate dielectric, and surpassed only by ultra-thin SAM gate dielectrics.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2127-2128
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• 2012

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.10
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• pp.665-671
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• 2017

Herein, we report the fabrication of low-voltage N-type organic field-effect transistors by using high capacitance fluorinated polymer gate dielectrics such as P(VDF-TrFE), P(VDF-TrFE-CTFE), and P(VDF-TrFE-CFE). Electron-withdrawing functional groups in PVDF-based polymers typically cause the depletion of negative charge carriers and a high contact resistance in N-channel organic semiconductors. Therefore, we incorporated intermediate layers of a low-k polymerto prevent the formation of a direct interface between PVDF-based gate insulators and the semiconducting active layer. Consequently, electron depletion is inhibited, and the high charge resistance between the semiconductor and source/drain electrodes is remarkably improved by the in corporation of solution-processed charge injection layers.

• 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 (${\Leq}-3V$).

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1046-1048
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• 2004

Performances of organic thin film transistors (OTFTs) can be detrimentally affected by the state of the gate dielectric. Because of the bad stability of polymers, OTFTs with polymer gate dielectrics often provide abnormal characteristics. In this study, we report the condensation effect of the polymer gate dielectric layer. For the observations of the effect of the condensation, the spin-coated polymer layers with various deposition conditions were fabricated and left under low vacuum condition for several days. It is observed that the thickness of polymer layer and the electrical characteristic of OTFTs vary with the condensation time.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.69.3-69.3
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• 2012

A high-performance low-voltage graphene field-effect transistor (FED array was fabricated on a flexible polymer substrate using solution-processable, high-capacitance ion gel gate dielectrics. The high capacitance of the ion gel, which originated from the formation of an electric double layer under the application of a gate voltage, yielded a high on-current and low voltage operation below 3 V. The graphene FETs fabricated on the plastic substrates showed a hole and electron mobility of 203 and 91 $cm^2/Vs$, respectively, at a drain bias of - I V. Moreover, ion gel gated graphene FETs on the plastic substrates exhibited remarkably good mechanical flexibility. This method represents a significant step in the application of graphene to flexible and stretchable electronics.

• ETRI Journal
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• v.33 no.6
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• pp.887-896
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• 2011

We investigated the effects of a gate dielectric and its solvent on the characteristics of top-gated organic field-effect transistors (OFETs). Despite the rough top surface of the inkjet-printed active features, the charge transport in an OFET is still favorable, with no significant degradation in performance. Moreover, the characteristics of the OFETs showed a strong dependency on the gate dielectrics used and its orthogonal solvents. Poly(3-hexylthiophene) OFETs with a poly(methyl methacrylate) dielectric showed typical p-type OFET characteristics. The selection of gate dielectric and solvent is very important to achieve high-performance organic electronic circuits.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.12
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• pp.1009-1013
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• 2009

In this study, we have been synthesized the dielectric layer using pure organic and organic-inorganic hybrid precursor on flexible substrate for improving of the organic thin film transistors (OTFTs) and, design and fabrication of organic thin-film transistors (OTFTs) using small-molecule organic semiconductors with pentacene as the active layer with record device performance. In this work OTFT test structures fabricated on polymerized substrates were utilized to provide a convenient substrate, gate contact, and gate insulator for the processing and characterization of organic materials and their transistors. By an adhesion development between gate metal and PI substrate, a PI film was treated using $O_2$ and $N_2$ gas. The best peel strength of PI film is 109.07 gf/mm. Also, we have studied the electric characteristics of pentacene field-effect transistors with the polymer gate-dielectrics such as cyclohexane and hybrid (cyclohexane+TEOS). The transistors with cyclohexane gate-dielectric has higher field-effect mobility, $\mu_{FET}=0.84\;cm^2/v_s$, and smaller threshold voltage, $V_T=-6.8\;V$, compared with the transistor with hybrid gate-dielectric.