• Journal of the Korean Ceramic Society
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• v.44 no.6 s.301
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• pp.303-307
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• 2007

Transparent In-doped zinc oxide (IZO) thin films are deposited with variation of pulsed DC power at Ar atmosphere on coming 7059 glass substrate by pulsed DC magnetron sputtering. A c-axis oriented IZO thin films were grown in perpendicular to the substrate. The optical transmittance spectra showed high transmittance of over 80% in the UV-visible region and exhibited the absorption edge of about 350 nm. Also, the IZO films exhibited the resistivity of ${\sim}10^{-3}{\Omega}\;cm$ and the mobility of ${\sim}6cm/V\;s$. Organic Light-emitting diodes (OLEDs) with IZO/N,N'-diphenyl-N, N'-bis(3-methylphenl)-1, 1'-biphenyl-4,4'-diamine (TPD)/tris (8-hydroxyquinoline) aluminum ($Alq_3$)/LiF/Al configuration were fabricated. LiF layer inserted is used as an interfacial layer to increase the electron injection. Under a current density of $100\;mA/cm^2$, the OLEDs show an excellent efficiency (9.4 V turn-on voltage) and a good brightness ($12000\;cd/m^2$) of the emission light from the devices. These results indicate that IZO films hold promise for anode electrodes in the OLEDs application.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.127-127
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• 2011

We investigate the transparent TFTs using a transparent ZnSnO3 (ZTO)/Ag/ZTO multilayer electrode as S/D electrodes with low resistivity of $3.24{\times}10^{-5}$ ohm-cm, and high transparency of 86.29% in ZTO based TFTs. The Transparent TFTs (TTFTs) are prepared on glass substrate coated 100 nm of ITO thin film. On atomic layer deposited $Al_2\;O_3$, 50 nm ZTO layer is deposited by RF magnetron sputtering through a shadow mask for channel layer using ZTO target with 1 : 1 molar ratio of ZnO : $SnO_2$. The power of 100W, the working pressure of 2mTorr, and the gas flow of Ar 20 sccm during the ZTO deposition. After channel layer deposition, a ZTO (35 nm)/Ag (12 nm)/ZTO(35 nm) multilayer is deposited by DC/RF magnetron sputtering to form transparent S/D electrodes which are patterned through the shadow mask. Devices are annealed in air at 300$^{\circ}C$ for 30 min following ZTO deposition. Using UV/Visible spectrometer, the optical transmittances of the TTFT using ZTO/Ag/ ZTO multilayer electrodes are compared with TFT using Mo electrode. The structural properties of ZTO based TTFT with ZTO/Ag/ZTO multilayer electrodes are analyzed by high resolution transmission electron microscopy (HREM) and X-ray photoelectron spectroscopy (XPS). The transfer and output characterization of ZTO TTFTs are examined by a customized probe station with HP4145B system in are.

• Korean Journal of Materials Research
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• v.31 no.1
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• pp.38-42
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• 2021

In this study, high temperature wetting analysis and AZ80/Ti interfacial structure observation are performed for the mixture of AZ80 and Ti, and the effect of Al on wetting in Mg alloy is examined. Both molten AZ80 and pure Mg have excellent wettability because the wet angle between molten droplets and the Ti substrate is about 10° from initial contact. Wetting angle decreases with time, and wetting phenomenon continues between droplets and substrate; the change in wetting angle does not show a significant difference when comparing AZ80-Ti and Mg-Ti. As a result of XRD of the lower surface of the AZ80-Ti sample, in addition to the Ti peak of the substrate, the peak of TiAl3, which is a Ti-Al intermetallic compound, is confirmed, and TiAl3 is generated in the Al enrichment region of the Ti substrate surface. EDS analysis is performed on the droplet tip portion of the sample section in which pure Mg droplets are dropped on the Ti substrate. Concentration of oxygen by the natural oxide film is not confirmed on the Ti surface, but oxygen is distributed at the tip of the droplet on the Mg side. Molten AZ80 and Ti-based compound phases are produced by thickening of Al in the vicinity of Ti after wetting is completed, and Al in the Mg alloy does not affect the wetting. The driving force of wetting progression is a thermite reaction that occurs between Mg and TiO2, and then Al in AZ80 thickens on the Ti substrate interface to form an intermetallic compound.

• Journal of the Korean Magnetics Society
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• v.2 no.3
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• pp.277-281
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• 1992

We have designed, fabricated and tested an integrated planar DC SQUID which incorporates input coil and mofulation coil in thin film structure. The SQUID uses Nb /Al-oxide /Nb Josephson junctions and Pd shunt resistors, and the SQUID loop incorporates two rings connected in series forming figure '8' structure and has the advantage of a negligibly small circulating current for the spatially homogeneous noise fields. The devices were fabricated using photolithographic technique, RF magnetron sputtering, anodic oxidation for insulation and lift-off process. The preliminary test of the fabricated SQUID at 4.2 K showed that the flux-voltage characteristics were smooth enough to adopt standard readout system, and the voltage noise was too small to be measured by direct method and so the white noise was thought to be less than $10^{-4}\;{\phi}_o/\;\sqrt{H_z}$.

• Composites Research
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• v.32 no.6
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• pp.368-374
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• 2019

Basalt fiber reinforced epoxy composites with inorganic filler (BFRP-F) such as Mg(OH)₂ (magnesium hydroxide), Al(OH)₃ (aluminum hydroxide), Al₂O₃ (aluminum oxide) and AlOOH (boehmite) were prepared by hand lay-up and hot pressing. The combustive properties of BFRP-F were improved comparing with basalt fiber reinforced epoxy composite (BFRP) without inorganic filler. At a 30 wt% resin content, the limited oxygen index (LOI) of BFRP is 28.9, which is higher than that of epoxy (21.4), and the LOI of BFRP-F is higher than that of BFRP. The BFRP-F showed the lower peak heat release rate (PHRR), total heat release (THR) and total smoke release rate (TSR) than those of BFRP. We confirmed that the flame retardant properties of the composite were improved by the addition of inorganic filler through the dehydration reaction and oxide film formation.

• Journal of Sensor Science and Technology
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• v.6 no.6
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• pp.476-482
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• 1997

A portable electronic nose system has been fabricated and characterized using an oxide semiconductor gas sensor array and pattern recognition techniques such as principal component analysis and back-propagation artificial neural network. The sensor array consists of six thick-film gas sensors whose sensing layers are Pd-doped $WO_{3}$, Pt-doped $SnO_{2}$, $TiO_{2}-Sb_{2}O_{5}-Pd$-doped $SnO_{2}$, $TiO_{2}-Sb_{2}O_{5}-Pd$-doped $SnO_{2}$ + Pd coated layer, $Al_{2}O_{3}$-doped ZnO and $PdCl_{2}$-doped $SnO_{2}$. The portable electronic nose system consists of an 16bit Intel 80c196kc as CPU, an EPROM for storing system main program, an EEPROM for containing optimized connection weights of artificial neural network, an LCD for displaying gas concentrations. As an application the system has been used to identify 26 carbon monoxide/hydrocarbon (CO/HC) car exhausting gases in the concentration range of CO 0%/HC 0 ppm to CO 7.6%/HC 400 ppm and the identification has been successfully demonstrated.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.148-148
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• 2017

Surface modification is a type of mechanical manipulation skills to achieve extensive aims including corrosion control, exterior appearance, abrasion resistance, electrical insulation and electrical conductivity of substrate materials by generating a protective surface using electrical, physical and chemical treatment on the surface of parts made from metallic materials. Such surface modification includes plating, anodizing, chemical conversion treatment, painting, lining, coating and surface hardening; this study conducted cavitation experiment to assess improvement of durability using anodizing. In order to observe surface characteristics with applied current density, the electrolyte temperature, concentration was maintained at constant condition. To prevent hindrance of stable growth of oxide layer due to local temperature increase during the experiment, stirring was maintained at constant speed. In addition, using galvanostatic method, it was maintained at processing time of 40minutes for 10 to $30mA/cm^2$. The cavitation experiment was carried out with an ultra sonic vibratory apparatus using piezo-electric effect with modified ASTM-G32. The peak-to-peak amplitude was $30{\mu}m$ and the distance between the horn tip and specimen was 1mm. The specimen after the experiment was cleaned in an ultrasonic bath, dried in a vacuum oven for more than 24 hours, and weighed with an electric balance. The surface damage morphology was observed with 3D analysis microscope. As a result of the study, differences were observed surface hardness and anti-cavitation characteristics depending on the development of oxide film with the anodizing process time.

• Journal of the Korean Ceramic Society
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• v.50 no.1
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• pp.63-69
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• 2013

Negative-temperature coefficient (NTC) thermistors based on nickel manganite spinel ($NiMn_2O_4$) are widely used for many applications, such as sensors and temperature compensators, due to their good thermistor characteristics and stabilities. However, to achieve thermistors with a high NTC B constant, which is an important figure of merit pertaining to the degree of temperature sensitivity, the activation energy should be high such that high resistivity at ambient temperatures results. To obtain a high B constant and low resistivity, Al and Si modified spinel structured $Ni_{0.6}Si_{0.2}Al_{0.6}Mn_{1.6}O_4$ hybrid thick films with the conducting metal oxide of $LaNiO_3$ were fabricated on a glass substrate by aerosol deposition at room temperature (RT). The NTC-$LaNiO_3$ hybrid thick films showed resistivity as low as < $100k{\Omega}\;cm$ at $90^{\circ}C$, which is one or two orders of magnitude lower than that of the monolithic NTC films, while retaining a high B constant of $NiMn_2O_4$ of over 5500 K when 20 wt% $LaNiO_3$ was added without a post-thermal treatment. These phenomena are explained by the percolation threshold mechanism.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.5-5
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• 2009

Thin-film-transistors (TFTs) that can be prepared at low temperatures have attracted much attention because of the great potential for transparent and flexible electronics. One of the mainstreams in this field is the use of organic semiconductors such as pentacene. But device performance of the organic TFTs is still limited due to low field-effect mobility and rapid degradation after exposing to air. Alternative approach is the use of amorphous oxide semiconductors as a channel. Amorphous oxide semiconductors (AOSs) based TFTs showed the fast technological development, because AOS films can be fabricated at room temperature and exhibit the possibility in application like flexible display, electronic paper, and larges solar cells. Among the various AOSs, a-IGZO has lots of advantages because it has high channel mobility, uniform surface roughness and good transparency. [1] The high mobility is attributed to the overlap of spherical s-orbital of the heavy post-transition metal cations. This study demonstrated the effect of the variation in channel thickness from 30nm to 200nm on the TFT device performance. When the thickness was increased, turn-on voltage and subthreshold swing was decreased. The a-IGZO channels and source/drain metals were deposited with shadow mask. The a-IGZO channel layer was deposited on $SiO_2$/p-Si substrates by RF magnetron sputtering, where RF power is 150W. And working pressure is 3m Torr, at $O_2/Ar$ (2/28 sccm) atmosphere. The electrodes were formed with electron-beam evaporated Ti (30 nm) and Au (70 nm) bilayer. Finally, Al (150nm) as a gate metal was thermal-evaporated. TFT devices were heat-treated in a furnace at 250 $^{\circ}C$ and nitrogen atmosphere for 1hour. The electrical properties of the TFTs were measured using a probe-station. The TFT with channel thickness of 150nm exhibits a good subthreshold swing (SS) of 0.72 V/decade and on-off ratio of $1{\times}10^8$. The field effect mobility and threshold voltage were evaluated as 7.2 and 8 V, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.5
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• pp.427-431
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• 2020

In this research, we evaluated the electrical properties of polycrystalline-gallium-oxIde (Ga₂O₃) thin films grown by mist-CVD. A 500~800 nm-thick Ga₂O₃ film was used as a channel in a fabricated bottom-gate MOSFET device. The phase stability of the β-phase Ga₂O₃ layer was enhanced by an annealing treatment. A Ti/Al metal stack served as source and drain electrodes. Maximum drain current (I_D) exceeded 1 mA at a drain voltage (V_D) of 20 V. Electron mobility of the β-Ga₂O₃ channel was determined from maximum transconductance (g_m), as approximately, 1.39 ㎠/Vs. Reasonable device characteristics were demonstrated, from measurement of drain current-gate voltage, for mist-CVD-grown Ga₂O₃ thin films.