• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1546-1548
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• 2002

In this paper, the electrical characteristics of pentacene thin film transistors(TFTs) with stacked and surface-treated gate insulators have been investigated. The semiconductor layer of pentacene was thermally evaporated onto the stacked gate insulators. For the gate insulating materials. PVP(PolyvinylPhenol) and polystyrene were spin-coated with two different stacking orders, PVP-polystyrene and polystyrene-PVP. Rapid solvent evaporation during the spin-coating processes of these insulating layers produces non-equilibrium phase morphologies accompanied by surface undulations on gate insulator interfaces. This non-equilibrium phase morphology affects the growth mode of the subsequent pentacene layer. Therefore, in order to smoothen the gate dielectric surfaces, gate dielectric surfaces were rubbed laterally along the direction from the drain to the source TFTs with with stacked and surface-treated gate insulators have provided improved operational characteristics.

• Journal of the Optical Society of Korea
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• v.18 no.1
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• pp.45-49
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• 2014

Well-crystallized $BaSi_2O_5:Eu^{2+}$ phosphor films were synthesized by heat treatment of spin-coated BaO:Eu on $SiO_2$ glass. We investigated luminescence-structure properties of these phosphor films as a function of heat-treatment temperature. From x-ray diffraction patterns, our $BaSi_2O_5:Eu^{2+}$ phosphor films revealed that (111)- and (204)-crystal planes of $BaSi_2O_5$ crystal were dominantly increased with an increase of heat-treatment temperature. Photoluminescence intensities of $BaSi_2O_5:Eu^{2+}$ phosphor films were increased with amount of these crystal planes. It can be explained that $Eu^{2+}$ ions were stably occupied at specific crystal orientation of $BaSi_2O_5$ crystal, enhancing the luminescent intensities of $BaSi_2O_5:Eu^{2+}$ phosphor films. In addition, our $BaSi_2O_5:Eu^{2+}$ phosphor films had transmittance of 70% at 510 nm,.due to the dense morphology and specific crystallinity of $BaSi_2O_5:Eu^{2+}$ phosphor films.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.238-239
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• 2010

Dimethyl sulphoxide (DMSO) is one of the widely-used secondary dopants in order to enhance the conductivity of poly(3, 4-ethylenedioxy-thiophene):poly(styrene sulfonate) (PEDOT:PSS) film. In this work, we investigated the effect of DMSO doping in to PEDOT:PSS on the electrical performance of the bulk heterojunction photovoltaics consisting of poly(3-hexylthiophene-2, 5-diyl) and phenyl-C61-butyric acid methyl ester. Correlation between the power conversion efficiency and the mechanism of improving conductivity, surface morphology, and contact properties was examined. The PEDOT:PSS films, which contain different concentration of DMSO, have been prepared and annealed at different annealing temperatures. The mixture of DMSO and PEDOT:PSS was prepared with a ratio of 1%, 5%, 15%, 25%, 35%, 45%, 55% by volume of DMSO, respectively. The DMSO-contained PEDOT:PSS solutions were stirred for 1hr at $40^{\circ}C$, then spin-coated on the ultra-sonicated glass. The spin-coated films were baked for 10min at $65^{\circ}C$, $85^{\circ}C$, and $120^{\circ}C$ in air. In order to investigate the electrical performance, P3HT:PCBM blended film was deposited with thickness of 150nm on DMSO-doped PEDOT:PSS layer. After depositing 100nm of Al, the device was post-annealed for 30min at $120^{\circ}C$ in vacuum. The fabricated cells, in this study, have been characterized by using several techniques such as UV-Visible spectrum, 4-point probe, J-V characteristics, and atomic force microscopy (AFM). The power conversion efficiency (AM 1.5G conditions) was increased from 0.91% to 2.35% by tuning DMSO doping ratio and annealing temperature. It is believed that the improved power conversion efficiency of the photovoltaics is attributed to the increased conductivity, leading to increasing short-circuit current in DMSO-doped PEDOT:PSS layer.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1229-1231
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• 1997

In this work, PZT(20/80)/(80/20) heterolayered thin film that has the tetragonal and rhombohedral structure was fabricated by Sol-Gel method spin-coated on the Pt/Ti/$SiO_2$/Si substrate by turns. The thickness of PZT-1 film obtained by six-times of drying/sintering process was about 480[nm]. This procedure was repeated several times to form PZT heterolayered thim film. PZT-5 thin films with top layer of tetragonal PZT(20/80) thin film showed dense grain structure and PZT-6 thin film with top layer of rhombohedral PZT(80/20) thin film showed the microstructure without rosette. Dielectric constant increased with increasing the number of coatings, and it was about 13S5 at PZT-6 thin film. Dielectric loss was not depend on the number of coatings.

• Tribology and Lubricants
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• v.24 no.5
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• pp.255-263
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• 2008

Adhesion tests were conducted to investigate the adhesion characteristics between mold and thermoplastic polymer film. Coating of anti-sticking layer (ASL), a kind of polymer material, imprint pressure, and separation velocity were considered as the process conditions. A piece of fused silica without patterns on its surface was used as a mold and the thermoplastic polymer films were made on Si substrate by spin-coating the commercial polymer solution such as mr-I PMMA and mr-I 7020. The ASL was derived from (1H, 1H, 2H, 2H - perfluorooctyl) trichlorosilane($F_{13}$-OTS) and coated on the fused silica mold in vapor phase. The pull-off force was measured in various process conditions and the surfaces of the mold and the polymer film were observed after separation. It was found that the adhesion characteristics between the mold and the thermoplastic polymer film and the release performance of ASL were changed according to the process conditions. The ASL was effective to reduce the pull-off force and the damage of polymer film. In cases of the mold coated with ASL, the pull-off force did not depend on imprint pressure and separation velocity.

• 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.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.37-37
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• 2010

Silicate-silsesquioxane or siloxane-silsesquioxane hybrid thin films are strong candidates as matrix materials for ultra low dielectric constant (low-k) thin films. We synthesized the silicate-silsesquioxane hybrid resins from tetraethoxyorthosilicate (TEOS) and methyltrimethoxysilane (MTMS) through hydrolysis and condensation polymerization by changing their molar ratios ([TEOS]:[MTMS] = 7:3, 5:5, and 3:7), spin-coating on Si(100) wafers. In the case of [TEOS]:[MTMS] 7:3, the dielectric permittivity value of the resultant thin film was measured at 4.30, exceeding that of the thermal oxide (3.9). This high value was thought to be due to Si-OH groups inside the film and more extensive studies were performed in terms of electronic, ionic, and orientational polarizations using Debye equation. The relationship between the mechanical properties and the synthetic conditions of the silicate-silsesquioxane precursors was also investigated. The synthetic conditions of the low-k films have to be chosen to meet both the low orientational polarization and high mechanical properties requirements. In addition, we have investigated a new solution-based approach to the synthesis of semiconducting chalcogenide films for use in thin-film transistor (TFT) devices, in an attempt to develop a simple and robust solution process for the synthesis of inorganic semiconductors. Our material design strategy is to use a sol-gel reaction to carry out the deposition of a spin-coated CdS film, which can then be converted to a xerogel material. These devices were found to exhibit n-channel TFT characteristics with an excellent field-effect mobility (a saturation mobility of ${\sim}\;48\;cm^2V^{-1}s^{-1}$) and low voltage operation (< 5 V). These results show that these semiconducting thin film materials can be used in low-cost and high-performance printable electronics.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.187-193
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• 2005

The photocatalyst $TiO_2$ thin film was made from titanium (IV) isopropoxide, ethanol, and HCl by sol-gel method. The surface observation by SEM showed the sample that was coated 5 times at $500^{\circ}C$ had good properties. The component ratio, in atom% of O : Ti by EDX analysis, of 61 : 39 by spin coating was superior than dip coating. It was found that crystal structure changed from anatase phase to rutile phase as a function of the temperature of thin film fabrication, and this was measured by XRD. The photolysis efficiency of total organic compounds (TOC) by lighting UV beam on $TiO_2$ thin film showed 20%~65% within 1 h, and decreased slowly thereafter.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.83-86
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• 1998

Ferroelectric PZT(40/67)/PZT(60/40)heterolayered thin films were Prepared by the alkoxide-based Sol-Gel method. PZT(40/60) and PZT(60/40) stock solutions were made and spin-coated on the P7Ti/Si02/Si substrate alternately. These PZT(40/60) and PZT(60/40) films were dried at 300$^{\circ}C$ for 30min to remove organic materials and were sintered at 650$^{\circ}C$ for 1 hour to crystalize into a perovskite structure. The coating and heating procedure were repeated 6 times to form heterolayered films. Increasing the number of coating, coercive field was decreased. The relative dielectric constant, loss, remanent polarization and coercive field of the 4-coated PZT heterolayered were 1200, 4.1[%], 30.794[${\mu}$C/㎡] and 147.22[kV/cm], respectively.

• Electrical & Electronic Materials
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• v.9 no.2
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• pp.132-137
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• 1996

Pb(Zr$_{x}$Ti$_{1-x}$ )O$_{3}$ solutions prepared by sol-gel processing with different Zr/Ti ratio were coated on Pt/SiO$_{2}$/Si substrates using spin coating method. Coated films were annealed by rapid thermal annealing at 650.deg. C for 20sec to fabricate Pb(Zr, Ti)O$_{3}$ ferroelectric thin films. Electrical properties of the films such as dielectric constant and loss, ferroelectric hysteresis, fatigue, switching time, and leakage current were measured. Hysteresis of the films with different Zr/Ti ratio yield Pr ranging 10-21.mu.C/cm$^{2}$, E$_{c}$ ranging 37.5-137.5kV/cm. Hysteresis curve was changed from square-type to slim type according to increasing Zr contents. Switching time was faster than 180ns, and leakage current was about 20.mu.A/cm$^{2}$. The film underwent above 10$^{8}$ cycles of reversed polarization showed fatigue with increased coercive field and decreased remnant polarization.tion.