• Journal of Sensor Science and Technology
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• 제10권6호
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• pp.295-303
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• 2001

White emission thin film electroluminecent device was fabricated with ZnS for phosphor layers and BST ferroelectric thin film for insulating layers. The ZnS:Mn and $ZnS:SmF_3$ layers were used for emission of red color. Also the $ZnS:TbF_3$ and $ZnS:AgF_3$ layers were used to emission of green and blue color, respectively. And the fabrication conditions of the BST insulating layers were followings, that is, the composition ratio of target, substrate temperature, working pressure and operating gas ratio were $Ba_{0.5}Sr_{0.5}Ti_{0.3}$, $400^{\circ}C$, 30 mTorr and 9:1, respectively. The thickness of phosphor were 150 nm for each layers and the insulating layers of upper and bottom were 400 nm and 200 nm, respectively. The luminesence threshold voltage was $75\;V_{rms}$ and the maximum brightness of the thin film electroluminecent device was $3200\;cd/m^2$ at $100\;V_{rms}$.

• Journal of Sensor Science and Technology
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• 제12권3호
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• pp.103-111
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• 2003

A chromel-alumel thermoelectric flow sensor using $Si_3N_4/SiO_2/Si_3N_4$ thermal isolation membrane was fabricated. Temperature coefficient of resistance of thin film Pt-heater was about $0.00397/^{\circ}C$, and Seebeck coefficient of chromel-alumel thermocouple was about $36\;{\mu}V/K$. The sensor showed that thermoelectric voltage decreased as thermal conductivity of gas increased, and $N_2$-flow sensitivity increased as heater voltage increased or the distance between heater and thermocouple decreased. When heater voltage was about 2.5 V, $N_2$-flow sensitivity and thermal response time of the sensor were about $1.5\;mV/sccm^{1/2}$ and 0.18 sec., respectively. Linear range in flow sensitivity of the flow sensor was wider than that of Bi-Sb flow sensor.

• Journal of Sensor Science and Technology
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• 제4권1호
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• pp.51-63
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• 1995

Polycrystalline $CdS_{1-x}Se_{x}$ thin films were grown on ceramic substrate using a chemical bath deposition method. They were annealed at various temperature and X-ray diffraction patterns were measured by X-ray diffractometer in order to study $CdS_{1-x}Se_{x}$ polycrystal structure using extrapolation method of X-ray diffraction patterns for the CdS, CdSe samples annealed in $N_{2}$ gas at $550^{\circ}C$ it was found hexagonal structure which had the lattice constant $a_{0}=4.1364{\AA}$, $c_{0}=6.7129{\AA}$ in CdS and $a_{0}=4.3021{\AA}$, $c_{0}=7.0142{\AA}$ in CdSe, respectively. Hall effect on these samples was measured by Van der Pauw method and then studied on carrier density and mobility depending on temperature. We measured also spectral response, sensitivity(${\gamma}$), maximum allowable power dissipation and response time on these samples.

• Journal of Sensor Science and Technology
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• 제4권3호
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• pp.60-70
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• 1995

Polycrystalline $Cd_{1-x}Zn_{x}S$ thin film were grown on slide glass(corning-2948) substrate using a chemical bath deposition (C.B.D) method. They were annealed at various temperature and X -ray diffraction patterns were measured by X-ray diffractometor in order to study $Cd_{1-x}Zn_{x}S$ polycrystal structure using extrapolation method of X-ray diffraction patterns for the CdS, ZnS sample annealed in $N_{2}$ gas at $550^{\circ}C$. It was found hexagonal structure which had the lattice constant $a_{0}\;=\;4.1364{\AA}$, $c_{0}\;=\;6.7129{\AA}$ in CdS and $a_{0}\;=\;3.8062{\AA}$, $c_{0}\;=\;6.2681{\AA}$ in ZnS, respectively. Hall effect on these sample was measured by Van der Pauw method and then studied on carrier density and mobility depending on temperature. We measured also spectral response, sensitivity maximum allowable power dissipation and response time on these sample.

• Journal of the Society of Cosmetic Scientists of Korea
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• 제30권2호
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• pp.173-180
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• 2004

Nano sized ZnO particle as 20-30nm applies for material, pigments, rubber additives, gas sensors, varistors, fluorescent substance as well as new material such as photo-catalyst, sensitizer, fluorescent material. ZnO with a particle size in the range 20-30nm has provided to be an excellent UV blocking material in the cosmetics industry, which can be used in sunscreen product to enhance the sun protection factor and natural makeup effect. But pure ZnO particles application limits for getting worse wearing feeling. We make high-functional inorganic-composite that coated with nano-ZnO on the plate-type particle such as sericite, boron nitride and bismuthoxychloride. In this experiment, we synthesized composite powder using hydrothermal precipitation method. The starting material was ZnCl$_2$ Precipitation materials were used hexamethylenetetramine(HMT) and urea. We make an experiment with changing as synthesis factors that are concentrations of starting material, precipitation materials, nuclear formation material, reaction time, and reaction temperature. We analyzed composite powder's shape, crystallization and UV-blocking ability with FE-SEM, XRD, FT-IR, TGA-DTA, In vitro SPF test. The user test was conducted by product's formulator. In the results of this study, nanometer sized ZnD was coated regardless of the type of plate-powder at fixed condition range. When the coated plate-powders were applied in pressed powder product, the glaze of powder itself decreased, but natural make-up effect, spreadability, and adhesionability were increased.

• Journal of the Korean Crystal Growth and Crystal Technology
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• 제22권6호
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• pp.274-278
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• 2012

$TiO_2$ can be used optically and is applied on many areas such as gas sensor, solar cell and photocatalysis. Electrospun nanofibers have received great interest for development and utilization in some novel applications, such as chemical sensors, dye-sensitized solar cell and photo catalysis. In this study, pure $TiO_2$ and Ga-doped $TiO_2$ nanofibers synthesized by a modified electrospinning method. The Ga doped $TiO_2$ solution is prepared by mixing poly vinyl pyrrolidone, ethyl alcohol, and titanium (IV) isopropoxide. By electrospinning these sols, nanofibers were fabricated. These fibers are heat-treated at $800^{\circ}C$ in air. The prepared pure $TiO_2$ and Ga-doped $TiO_2$ nanofibers samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy.

• Journal of the Korean Vacuum Society
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• 제19권2호
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• pp.81-90
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• 2010

We introduce a novel and versatile approach for preparing self-assembled nanoporous multilayered films with antireflective properties. Protonated polystyrene-block-poly (4-vinylpyrine) (PS-b-P4VP) and anionic polystyrene-block-poly (acrylic acid) (PS-b-PAA) block copolymer micelles (BCM) were used as building blocks for the layer-by-layer assembly of BCM multilayer films. BCM film growth is governed by electrostatic and hydrogen-bonding interactions between the oppositely BCMs. Both film porosity and film thickness are dependent upon the charge density of the micelles, with the porosity of the film controlled by the solution pH and the molecular weight (Mw) of the constituents. PS7K-b-P4VP28K/PS2K-b-PAA8K films prepared at pH 4 (for PS7K-b-P4VP28K) and pH 6 (for PS2K-b-PAA8K) are highly nanoporous and antireflective. In contrast, PS7K-b-P4VP28K/PS2K-b-PAA8K films assembled at pH 4/4 show a relatively dense surface morphology due to the decreased charge density of PS2K-b-PAA8K. Films formed from BCMs with increased PS block and decreased hydrophilic block (P4VP or PAA) size (e.g., PS36K-b-P4VP12K/PS16K-b-PAA4K at pH 4/4) were also nanoporous. Furthermore, we demonstrate that the nanostructured electrochemical sensors based on patterning methods show the electrochemical activities. Anionic poly(styrene sulfonate) (PSS) layers were selectively and uniformly deposited onto the catalase (CAT)-coated surface using the micro-contact printing method. The pH-induced charge reversal of catalase can provide the selective deposition of consecutive PE multilayers onto patterned PSS layers by causing the electrostatic repulsion between next PE layer and catalase. Based on this patterning method, the hybrid patterned multilayers composed of platinum nanoparticles (PtNP) and catalase were prepared and then their electrochemical properties were investigated from sensing $H_2O_2$ and NO gas. This study was based on the papers reported by our group. (J. Am. Chem. Soc. 128, 9935 (2006); Adv. Mater. 19, 4364 (2007); Electro. Mater. Lett. 3, 163 (2007)).

• Journal of Sensor Science and Technology
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• 제5권6호
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• pp.51-59
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• 1996

A flow sensor has been fabricated by preparing thin film Pt-heater and Bi-Sb thermocouples array on 150 nm-$Si_{3}N_{4}$/300 nm-$SiO_{2}$/150 nm-$Si_{3}N_{4}$ dielectric diaphragm which has low thermal conductivity and balanced stress with silicon substrate for the purpose of improving the thermal isolation between heater and silicon substrate. Pt-heater showed nonlinear I-V characteristics due to the thermal isolation effect of the diaphragm. Its temperature coefficient of resistance was about $0.00378\;/^{\circ}C$ and Seebeck coefficient of Bi-Sb thermocouple was about $97\;{\mu}V/K$. The sensor showed that thermoelectric voltage decreased as thermal conductivity of gas increased, and flow sensitivity increased as heater voltage increased or as the distance between heater and thermocouple decreased. When heater voltage was about 2.5 V, $N_{2}$-flow sensitivity and thermal response time of the sensor were about $1.27\;mV{\cdot}(sccm)^{-1/2}$ and 0.13 sec., respectively.

• Journal of Sensor Science and Technology
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• 제2권1호
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• pp.3-10
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• 1993

Polycrystalline CdS thin films were grown on ceramic substrate using a chemical bath deposition method. They were annealed at various temperature and X-ray diffraction patterns were measured by X-ray diffractometer in order to study CdS polycrystal structure. Using extrapolation method of X-ray diffraction patterns for the CdS samples annealed in $N_{2}$ gas at $550^{\circ}C$ it was found hexagonal structure whose lattice constants $a_{o}$ and $c_{o}$ were $4.1364{\AA}$ and $6.7129{\AA}$, respectively. Its grain size was about $0.35{\mu}m$. Hall effect on this sample was measured by Van der Pauw method and studied on carrier density and mobility defending on temperature. From Hall data, the mobility was likely to be decreased by piezo electric scattering at temperature range of 33K and 150k and by polar optical scattering at temperature range of 150K and 293K. We measured also spectral response, sensitivity (${\gamma}$), maximum allowable power dissipation and response time on these samples.

• Journal of Sensor Science and Technology
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• 제2권1호
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• pp.81-86
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• 1993

Polycrystalline CdSe thin films were grown on ceramic substrate using a chemical bath deposition (CBD) method. They were annealed at various temperature and X-ray diffraction patterns were measured by X-ray diffractometer in order to study CdSe polycrystal structure. Using extrapolation method of X-ray diffraction patterns for the CdSe samples annealed in $N_{2}$ gas at $450^{\circ}C$ it was found hexagonal structure whose lattice parameters $a_{o}$ and $c_{o}$ were $4.302{\AA}$ and $7.014{\AA}$, respectively. Its grain size was about $0.3{\mu}m$. Hall effect on this sample was measured by Van der Pauw method and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by piezo electric scattering at temperature range of 33 K and 200 K, and by polar optical scattering at temperature range of 200 K and 293 K. We measured also spectral response, sensitivity (${\gamma}$), maximum allowable power dissipation and response time on these samples.