• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.130-131
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• 2007

In this study, polyvinylidene fluoride/trifluoroethylene (PVDF-TrFE) was investigated. For a metal-ferroelectic-metal (MFM) structure, We obtained that the 70 nm-thick film showed the maximum polarization of $8.24\;{\mu}C/cm^2$, 2Pr of $6\;{\mu}C/cm^2$ and the coercive voltage of ${\pm}3.1\;V$ at 12 V. The 140 nm-thick film showed higher performance. However, the thicker film required a higher voltage. The current density was $10^{-6}{\sim}10^{-7}\;A/cm^2$ under 15 V. We can expect from these results that the electrical properties of the devices particularly ferroelectric thin film transistor using PVDF-TrFE copolymer, be able to be on the trade-off relationship between the remanent polarization and the leakage current.

• Progress in Superconductivity and Cryogenics
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• v.6 no.3
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• pp.21-26
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• 2004

Deposition condition of YBa$_2$Cu$_3$$O_{7-x}$ (YBCO) films on moving IBAD templates (CeO$_2$/IBAD-YSZ/SS) was studied in a hot-wall type metal organic chemical vapor deposition (MOCVD) process using single liquid source. The reel velocity was 40 cm/hr and the source mole ratios of Y(tmhd)$_3$:Ba(tmhd)$_2$:Cu(tmhd)$_2$ were 1:2.3:3.1 and 1:2.1:2,9, Two different types of IBAD templates with thin CeO$_2$ and thick CeO$_2$ layers were used, The YBCO films were successfully deposited at the deposition temperatures of 780~89$0^{\circ}C$ ; the a-axis growth was observed together with the c-axis growth up to 83$0^{\circ}C$. while the c-axis growth became dominant above 83$0^{\circ}C$. The top surface of the c-axis film was fairly dense and included a small amount of the a-axis growth, although the peaks of the a-axis grains were not observed in XRD pattern, The YBCO film deposited on IBAD template with thin CeO$_2$ layer showed low critical current of 2.5 A/cm-width. while the YBCO film deposited on IBAD template with thick CeO$_2$ layer showed higher critical current of 50 A/cm-width. This result indicates that thick CeO$_2$ layer is thermally more stable than thin CeO$_2$ layer at the high deposition temperature of the MOCVD process.s.

• Advances in nano research
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• v.2 no.3
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• pp.173-177
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• 2014

This study is aimed to the numerical modeling of the surface plasmon-polariton excitation by a layer of active (electrically pumped) quantum dots embedded in a semiconductor, covered with a metal. It is shown that this excitation becomes much more efficient if the metal has a form of a thin (with thickness of several nanometers) film. The cause of this enhancement in comparison with a thick covering metal film is the partial surface plasmon-polariton localized at the metal-semiconductor interface penetration into air. In result the real part of the metal+air half-space effective dielectric function becomes closer (in absolute value) to the real part of the semiconductor dielectric function than in the case of a thick covering metal film. This leads to approaching the point of the surface plasmon-polariton resonance (where absolute values of these parts coincide) and, therefore, the enhancement of the surface plasmon-polariton excitation. The calculations were made for a particular example of InAs quantum dot layer embedded in GaAs matrix covered with an Au film. Its results indicate that for the 10 nm Au film the rate of this excitation becomes by 2.5 times, and for the 5 nm Au film - by 6-7 times larger than in the case of a thick (40 nm or more) Au film.

• Korean Journal of Materials Research
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• v.26 no.8
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• pp.417-421
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• 2016

We improve the energy conversion efficiency (ECE) of a dye sensitized solar cell (DSSC) by preparing a working electrode (WE) with localized surface plasmon resonance (LSPR) by inducing Au thin films with thickness of 0.0 to 5.0 nm, deposited via sputtering. Field emission scanning electron microscopy and atomic force microscopy were used to characterize the microstructure of the blocking layer (BL) of the Au thin films. Micro-Raman measurement was employed to confirm the LSPR effect, and a solar simulator and potentiostat were used to evaluate the photovoltaic properties, including the impedance and the I-V of the DSSC of the Au thin films. The results of the microstructural analysis confirmed that nano-sized Au agglomerates were present at certain thicknesses. The photovoltaic results show that the ECE reached a value of 5.34% with a 1-nm thick-Au thin film compared to the value of 5.15 % without the Au thin film. This improvement was a result of the increase in the LSPR of the $TiO_2$ layer that resulted from the Au thin film coating. Our results imply that the ECE of a DSSC may be improved by coating with a proper thickness of Au thin film on the BL.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.121-121
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• 1999

Gallium nitride (GaN) semiconductor is intensively under investigation for commercialization of short wavelength light emitting devices and laser diodes. One of serious obstacles to overcome is to reduce the defect density in GaN film grown by various techniques such as MOCVD, HVPE, etc. Many research groups including SAIT are trying to improve the defect density to 106-107/cm2 from the level of 108-1010/cm2. We have investigated epitaxial growth behaviour of GaN thin and thick films under hidride vapour phase epitaxy (HVPE) condition. In this report, we present the microstructural and crystallographical characteristics of the GaN films grown on sapphire (0001) substrate which were studied by both conventional and high-resolution transmission electron microscopy (TEM). Also we present some microscopic analysis results obtained from GaN films grown by ELO(dpitzsial lateral overgrowth)-HVPE and from GaN quantum well structures grown by MOCVD. Another serious problem in growing GaN thick film by HVPE is internal micro-cracks. We also comment the origin of the micro-crack.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.8
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• pp.474-478
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• 2017

We report on thin-film transistors based on $TiO_x$ pre-annealed by femtosecond laser pulses. A 30-nm thick $TiO_x$ active channel layer was initially deposited by an ALD system. The $TiO_x$ semiconducting films were annealed by irradiation with a femtosecond laser (power: $3W/cm^2$) for 5, 25, and 50s. Atomic force microscopy images revealed that the surface of a $TiO_x$ film without femtosecond laser pre-annealing was relatively rough, while after annealing with femtosecond laser pulses, the surface of the $TiO_x$ films became smooth. With increasing radiation time, the surrounding gas atmosphere could have a larger impact on the $TiO_x$ surface; meanwhile, the thin-film roughness decreased. Thin-film transistors with $TiO_x$ active channels pre-annealed at 50s exhibited good transfer characteristics and an on-to-off current ratio of ${\sim}10^3$.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.3
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• pp.19-26
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• 2017

Stretchable deformation-resistance characteristics of Au, Pt, and Cu films were measured for the stretchable packaging structure where a parylene F was used as an intermediate layer between a PDMS substrate and a metal thin film. The 150 nm-thick Au and Pt films, sputtered on the parylene F-coated PDMS substrate, exhibited the initial resistances of $1.56{\Omega}$ and $5.53{\Omega}$, respectively. The resistance increase ratios at 30% tensile strain were measured as 7 and 18 for Au film and Pt film, respectively. The 150 nm-thick Cu film, sputtered on the parylene F-coated PDMS substrate, exhibited a very poor stretchability compared to Au and Pt films. Its resistance was initially $18.71{\Omega}$, rapidly increased with applying tensile deformation, and finally became open at 5% tensile strain.

• 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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• 2008.10a
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• pp.831-833
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• 2008

150 nm thick Ga-doped ZnO thin film, which was deposited by a sputtering process, was wet-chemically etched by using various organic acids such as oxalic, citric and formic acid. Wet etch parameters including etchant concentration and temperature are investigated for each etchant, and their effects on the etch rate and the feature of edge line are compared.

• Solar Energy
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• v.8 no.2
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• pp.73-76
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• 1988

Thick films based on the mature crystalline silicon technology are expected to exhibit eversmaller cost reduction. The thin-film-based technology is, however, expected to exhibit a much sharper drop in cost as it develops. In this report, technology and recent R & D of thin film solar cell, such as amorphous silicon, cadnium telluride, copper indium diselenide and gallium arsenide, are described. Perspectives of world photovoltaic market and solar cell price are also described.