• Proceedings of the Korean Vacuum Society Conference
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• 2007.02a
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• pp.108-108
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• 2007

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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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.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1754-1756
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• 2000

Organic semiconductors based on fused-ring polycyclic aromatic hydrocarbon have great potential to be utilized as an active layer for electronic and optoelectronic devices. In this study, pentacene thin films and electrode materials were deposited by Organic Molecular Beam Deposition(OMBD) and vacuum evaporation respectively. For the gate dielectric, polyamic acid was spin-coated and cured into polyimide at 350$^{\circ}C$. Electrical characteristics of the devices were investigated, where the channel length and width was 50${\mu}m$ and 5mm. It was found that field effect mobility was 0.012$cm^{2}/Vs$, and on/off current ratio was $10^5$.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.4
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• pp.161-168
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• 2001

Organic thin film transitors(TFTs) are of interest for use in broad area electronic applications. For example, in active matrix liquid crystal displays(AMLCDs), organic TFTs would allow the use of inexpensive, light-weight, flexible, and mechanically rugged plastic substrates as an alternative to the glass substrates needed for commonly used hydrogenated amorphous silicon(a-Si:H). Recently pentacene TFTs with carrier field effect, mobility as large as 2 $cm^2V^{-1}s^{-1}$ have been reported for TFTs fabricated on silicon substrates, and it is higher than that of a-Si:H. But these TFTs are fabricated on silicon wafer and $SiO_2$ was used as a gate insulator. $SiO_2$ deposition process requires a high insulator which is polyimide and photo acryl. We investigated trasfer and output characteristics of the thin film transistors having active layer of pentacene. We calculated field effect mobility and on/off ratio from transfer characteristics of pentacene thin film transistor, and measured IR absorption spectrum of polymide used as the gate dielectric layer. It was found that using the photo acryl as a gate insulator, threshold voltage decreased from -12.5 V to -7 V, field effect mobility increased from 0.012 $cm^2V^{-1}s^{-1}$ to 0.039 $cm^2V^{-1}s^{-1}$ , and on/off current ratio increased from $10^5\;to\;10^6$. It seems that TFTs using photo acryl gate insulator is apt to form channel than TFTs using polyimide gate insulator.

• Journal of Adhesion and Interface
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• v.23 no.2
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• pp.53-58
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• 2022

Here, the surface characteristics of the dielectric were controlled by introducing the self-assembled monolayers (SAMs) as the intermediate layers on the surface of the AlOx dielectric, and the electrical performances of the organic charge modulated transistor (OCMFET) were significantly improved. The organic intermediate layer was applied to control the surface energy of the AlOx gate dielectric acting as a capacitor plate between the control gate (CG) and the floating gate (FG). By applying the intermediate layers on the gate dielectric surface, and the field-effect mobility (μ_OCMFET) of the OCMFET devices could be efficiently controlled. We used the four kinds of SAM materials, octadecylphosphonic acid (ODPA), butylphosphonic acid (BPA), (3-bromopropyl)phosphonic acid (BPPA), and (3-aminopropyl)phosphonic acid (APPA), and each μ_OCMFET was measured at 0.73, 0.41, 0.34, and 0.15 cm2V-1s-1, respectively. The results could be suggested that the characteristics of each organic SAM intermediate layer, such as the length of the alkyl chain and the type of functionalized end-group, can control the electrical performances of OCMFET devices and be supported to find the optimized fabrication conditions, as an efficient sensing platform device.

• Journal of Electrical Engineering and Technology
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• v.6 no.6
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• pp.836-841
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• 2011

Plasma polymerized methyl methacrylate (ppMMA) thin films were deposited by plasma polymerization technique with different plasma powers and subsequently thermally treated at temperatures of 60 to $150^{\circ}C$. To find a better ppMMA preparation technique for application to organic thin film transistor (OTFT) as dielectric layer, the chemical composition, surface morphology, and electrical properties of ppMMA were investigated. The effect of ppMMA thin-film preparation conditions on the resulting thin film properties were discussed, specifically O-H site content in the pMMA, dielectric constant, leakage current density, and hysteresis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.158-158
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• 2009

This paper focuses on improving organic thin film transistor (OTFT) characteristics by controlling the self-organization of pentacene molecules with an alignable high-dielectric-constant film. The process, based on the growth of pentacene film through high-vacuum sublimation, is a method of self-organization using ion-beam (IB) bombardment of the $HfO_2/Al_2O_3$ surface used as the gate dielectric layer. X-ray photoelectron spectroscopy indicates that the IB raises the rate of the structural anisotropy of the $HfO_2/Al_2O_3$film, and X-ray diffraction patterns show the possibility of increasing the anisotropy to create the self-organization of pentacene molecules in the first polarized monolayer. An effective mobility of $2.3{\times}10^{-3}cm^2V^{-1}s^{-1}$ was achieved, which is significantly different from that of pentacene films that are not aligned. The proposed OTFT devices with an ultrathin $HfO_2$ structure as the gate dielectric layer were operated at a gate voltage lower than 5 V.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.67.1-67.1
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• 2012

Graphene has attracted much attention for future nanoelectronics due to its superior electrical properties. Owing to its extremely high carrier mobility and controllable carrier density, graphene is a promising material for practical applications, particularly as a channel layer of high-speed FET. Furthermore, the planar form of graphene is compatible with the conventional top-down CMOS fabrication processes and large-scale synthesis by chemical vapor deposition (CVD) process is also feasible. Despite these promising characteristics of graphene, much work must still be done in order to successfully develop graphene FET. One of the key issues is the process technique for gate dielectric formation because the channel mobility of graphene FET is drastically affected by the gate dielectric interface quality. Formation of high quality gate dielectric on graphene is still a challenging. Dirac voltage, the charge neutral point of the device, also strongly depends on gate dielectrics. Another performance killer in graphene FET is source/drain contact resistance, as the contact resistant between metal and graphene S/D is usually one order of magnitude higher than that between metal and silicon S/D. In this presentation, the key issues on graphene-based FET, including organic-inorganic hybrid gate dielectric formation, controlling of Dirac voltage, reduction of source/drain contact resistance, device structure optimization, graphene gate electrode for improvement of gate dielectric reliability, and CVD graphene transfer process issues are addressed.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.59.1-59.1
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• 2007

• Proceedings of the Korean Vacuum Society Conference
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• 2006.08a
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• pp.173-173
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• 2006