• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.8
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• pp.484-490
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• 2017

We investigated the rewritable operation of a non-volatile memory device composed of Al (top)/$TiO_2$/indium-zinc-oxide (IZO)/Al (bottom). The oxygen-deficient IZO layer of the device was spin-coated with 0.1 M indium nitrate hydrate and 0.1 M zinc acetate dehydrate as precursor solutions, and the $TiO_2$ layer was fabricated by atomic layer deposition. The oxygen vacancies IZO layer of an active component annealed at $400^{\circ}C$ using thermal annealing and it was proven to be in oxygen vacancies and oxygen binding environments with OH species and heavy metal ions investigated by X-ray photoelectron spectroscopy. The device, which operates at low voltages (less than 3.5 V), exhibits non-volatile memory behavior consistent with resistive-switching properties and an ON/OFF ratio of approximately $3.6{\times}10^3$ at 2.5 V.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.809-812
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• 2004

(Pb,Sr)TiO3 (PST) thin films were fabricated by using the alkoxide-based sol-gel method. The PST stock solution was made and then spin-coated onto a PUTi/SiO2/Si substrate. The coating and drying procedures were repeated several times, and the PST thin films were sintered at 450-650 C for 1 h. All PST thin films showed dense and homogeneous structures without the presence of any rosette structure. The thicknesses of the PST thin films were approximately 200 nm. The dielectric constant and the dielectric loss of the PST thin films sintered at 550 C were about 404 and 0.0023, respectively. The leakage current density of the PST thin film sintered at 550 C was 3.13 x 10-8 A/cm2 at 1 V.

• Journal of the Korean Ceramic Society
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• v.39 no.9
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• pp.884-889
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• 2002

In order to investigate the calcium phosphate forming ability of nanocrystalline $ZrO_2$ film, we prepared $ZrO_2/Si$ structure by using a chemical solution deposition with a zirconium naphthenate as a starting material. Precursor sol was spin-coated onto the (100)Si substrate and prefired at 500$^{\circ}C$ for 10 min in air, followed by final annealing at 800$^{\circ}C$ for 30 min in air. Crystallinity of the annealed film was examined by X-ray diffraction analysis. Surface morphology and surface roughness of the film were characterized by field emission-scanning electron microscope and atomic force microscope. After annealing, nanocrystalline $ZrO_2$ grains were obtained on the surface of the film with a homogeneous interface between the film and substrate. After immersion for 1 or 5 days in a simulated body fluid, formation of calcium phosphate was observed on $ZrO_2$ film annealed at 800$^{\circ}C$ by energy dispersive X-ray spectrometer. The fourier transform infrared spectroscopy revealed that carbonate was substituted into the calcium phosphate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.140-140
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• 2009

The Metal-ferroelectric-semiconductor (MFS) structure has superior advantages such as high density integration and non-destructive read-out operation. However, to obtain the desired electrical characteristics of an MFS structure is difficult because of interfacial reactions between ferroelectric thin film and Si substrate. As an alternative solution, the MFS structure with buffer insulating layer, i.e. metal-ferroelectric-insulator-semiconductor (MFIS), has been proposed to improve the interfacial properties. Insulators investigated as a buffer insulator in a MFIS structure, include $Ta_2O_5$, $HfO_2$, and $ZrO_2$ which are mainly high-k dielectrics. In this study, we prepared the Dy-doped $La_2O_3$ solution buffer layer as an insulator. To form a Dy-doped $La_2O_3$ buffer layer, the solution was spin-coated on p-type Si(100) wafer. The coated Dy-doped $La_2O_3$ films were annealed at various temperatures by rapid thermal annealing (RTA). To evaluate electrical properties, Au electrodes were thermally evaporated onto the surface of the samples. Finally, we observed the surface morphology and crystallization quality of the Dy-doped $La_2O_3$ on Si using atomic force microscopy (AFM) and x-ray diffractometer (XRD), respectively. To evaluate electrical properties, the capacitance-voltage (C-V) and current density-voltage (J-V) characteristics of Au/Dy-doped La2O3/Si structure were measured.

• Polymer(Korea)
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• v.30 no.3
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• pp.207-209
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• 2006

We fabricated a capacitive-type humidity sensor using poly (p-phenylene ether sulfone: PES) as a humidity sensitive layer. The PES was dissolved in m-cresol $(CH_3C_6H_4OH)$ and spin-coated on ITO-coated glass substrate. Gold was deposited by sputtering as a water-permeable upper electrode. The capacitance of the sensor was inversely proportional to sensing film thicknesses and showed an excellent linearity of less than 1% in the humidity range of 20 to 90%. The sensor haying a $1.4{\mu}m$ sensing layer showed a hysteresis of 1.3% and a good sensitivity of 1.14 at 20 kHz.

• Macromolecular Research
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• v.12 no.6
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• pp.581-585
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• 2004

A copolymer P[OSA-MI] was synthesized by copolymerization of its corresponding monomers, N-phenyl maleimide (MI) and 2-octen-l-ylsuccinic anhydride (OSA). The polymer (poly[2-[1-(2,5-dioxo-l-phenylpyrroli­din-3-ylmethyl)heptyl]-succinic acid 4-(2-$\{$ethyl-[4-(4-nitrophen-ylazo)phenyl]amino$\}$ethyl)ester]) P[DR1MA-MI] was obtained from the reaction of P[OSA-MI] with 2-[4-(4-nitrophenylazo)-N-ethylphenylamino] ethanol (DR1). A stable monolayer of P[DRIMA-MI] was formed by spreading the solution of the polymer in chloroform. In Y-type Langmuir-Blodgett (LB) films prepared using this Langmuir-Blodgett method, the second harmonic waves generated from adjacent mono layers canceled each other out. In X-and Z-type LB films, the second harmonic intensity increased upon increasing the number of monolayers, but this increase was somewhat smaller than predicted by the square law. This phenomenon is due to defects or imperfect alignment of the dipoles in the LB film. The generation of second harmonic waves from Y-type LB films having an even number of mono layers supports this argument. The degree of imperfection seemed to increase as the number of layers increased. The second-order nonlinear optical properties of spin-cast films of these polymers were also measured. The largest second harmonic coefficient of the poled P[DRIMA-MI] film coated on a glass plate was 19 pm/V.

• Journal of the Korean Vacuum Society
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• v.13 no.1
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• pp.39-45
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• 2004

Ultraviolet-nanoimprint lithography (UV-NIL) is a promising method for cost-effectively defining nanoscale structures at room temperature and low pressure. A 5${\times}$5${\times}$0.09 in. quartz stamp is fabricated using the etch process in which a Cr film was employed as a hard mask for transferring nanostructures onto the quartz plate. FAS(Fluoroalkanesilane) is used as a material for anti-adhesion surface treatment on the stamp and a thin organic film to improve adhesion on a wafer is formed by spin-coating. The low viscosity resin droplets with a nanometer scale volume are dispensed on the whole area of the coated wafer. The UV-NIL experiments have been performed using the EVG620-NIL. 370 nm - 1 m features on the stamp have been transferred to the thin resin layer on the wafer using the multi-dispensing method and UV-NIL process. We have measured the imprinted patterns and residual layer using SEM and AFM to evaluate the potential of the process.

• Korean Journal of Materials Research
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• v.20 no.11
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• pp.611-616
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• 2010

A cobalt oxide - tin oxide nanocomposite based gas sensor on an $SiO_2$ substrate was fabricated. Granular thin film of tin oxide was formed by a rheotaxial growth and thermal oxidation method using dc magnetron sputtering of Sn. Nano particles of cobalt oxide were spin-coated on the tin oxide. The cobalt oxide nanoparticles were synthesized by polymer-assisted deposition method, which is a simple cost-effective versatile synthesis method for various metal oxides. The thickness of the film can be controlled over a wide range of thicknesses. The composite structures thus formed were characterized in terms of morphology and gas sensing properties for reduction gas of $H_2$. The composites showed a highest response of 240% at $250^{\circ}C$ upon exposure to 4% $H_2$. This response is higher than those observed in pure $SnO_2$ (90%) and $Co_3O_4$ (70%) thin films. The improved response with the composite structure may be related to the additional formation of electrically active defects at the interfaces. The composite sensor shows a very fast response and good reproducibility.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.4
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• pp.312-317
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• 2000

Ferroelectric S $r_{0.9}$/B $i_{2.1}$/T $a_{2}$/ $O_{9}$ solutions were synthesized using sol-gel process in which strontinum ethoxide bismuth ethoxide trantalum ethoxide were used a s startring materials. SBT thin films were coated on Pt/Ti/ $SiO_2$/Si substrates by spin-coating. rapid thermal annealing (RTA) was used to promote crystallization. Thin films were annealed at $700^{\circ}C$ for 1 hr in an oxygen atmosphere. This temperature is about 10$0^{\circ}C$ lower than the usual annealing temperature for SBT thin films. Pt top-electrode was deposited by sputtering and thin films were post-annealed at $700^{\circ}C$ for 30 min. to enhance electrical properties. As the RTA temperature increased the higher 2 $P_{r}$ values were obtained. At RTA temperature being 78$0^{\circ}C$ remanent polarization of S $r_{0.9}$/B $i_{2.1}$/T $a_{2}$/ $O_{9}$ thin film was 7.73 $\mu$C/cm $_2$ and the leakage current density was 1.14$\times$10$^{-7}$ A/c $m^2$ at 3 V. As RTA temperature increased the breakdown voltage was decreased. It is considered that the low-field breadown is caused by the rough surface of SBT films and forming bismuth metal in SBT thin films.films.lms.

• Journal of Korean Ophthalmic Optics Society
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• v.5 no.2
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• pp.187-192
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• 2000

We prepared $SiO_2-Na_2O-R_mO_n$ thin films based on economics of water glass and investigated optical, mechanical properties of product thin films. Coating sol stabilized with 1 N HCl and 1 N $NH_4OH$, was fabricated by using water glass and calcium nitrate, and aluminum nitrate as starting materials. As-coated films on stainless steel, Si wafer and soda-lime-silica glass by spinning were finally annealed at 500, 750 and $900^{\circ}C$. Micro hardness and nitrogen content in film surface of annealed films were measured by Knoop hardness tester and EDX, respectively. Field Emission Scanning Electron Microscope (FE-SEM) and UV-VIS spectroscopy were adopted to analyze surface morphology and thickness and reflectance of our films.