• Journal of the Korean Ceramic Society
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• v.34 no.4
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• pp.387-393
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• 1997

In order to apply WO3 thin films to the semiconducting NOx gas sensors as a sensing material, which have been expected to show good electrical properties, such as large sensitivity, rapid responsibility, and high selectivity, the fabrication method and their sensing characteristics were studied. The variations of surface morphologies, crystallographic orientations and crystallinity with the WO3 thin film growing methods thermal evaporation and DC sputtering methods were investigated by using scanning electron microscopy (SEM) and X-ray diffraction(XRD) analysis. As a result of sensitivity (Rgas/Rair) measurements for the 5 ppm NO2 test gas, the sensitivity values were 113 for the sputtered films and 93 for the evaporated films. It was also observed that the recovery rate of a sensing signal after measuring sensitivity was faster in the sputtered films than in the evaporated films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.3
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• pp.275-280
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• 2022

An all-solid-state electrochromic film was fabricated by laminating tungsten oxide (WO₃) and nickel oxide (NiO) thin films deposited by a reactive DC magnetron sputtering on flexible ITO films. The influence of oxygen partial pressure on the crystal structure, microstructure, optical properties, and electrochromic properties of WO₃ and NiO thin films were investigated. WO₃ and NiO films showed the best electrochromic properties under the flow of Ar:O₂=80:20 and Ar:O₂=90:10, respectively. The EC film fabricated with an optimized WO₃ and NiO films showed a high coloration efficiency, a fast response time, and a stable optical modulation. It is expected that flexible EC window films will pave the way for the next-generation energy-saving windows.

• Proceedings of the Materials Research Society of Korea Conference
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• 1998.08a
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• pp.117.2-117
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• 1998

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.6
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• pp.582-587
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• 2023

The effects of the annealing temperature on the structural, morphological, and luminescent properties of SrWO₄:Sm³⁺ thin films grown on quartz substrates by radio-frequency magnetron sputtering were investigated. The thin films were annealed at various annealing temperatures for 20 min in a rapid thermal annealer after growing the thin films. The experimental results showed that the annealing temperature has a significant effect on the properties of the SrWO₄:Sm³⁺ thin films. The crystal structure of the as-grown SrWO₄:Sm³⁺ thin films was transformed from amorphous to crystalline after annealing at 800℃. The preferred orientation along (112) plane and a significant increase in average grain size by 820 nm were observed with increasing the annealing temperature. The average optical transmittance in the wavelength range of 500~1,100 nm was decreased from 72.0% at 800℃ to 44.2% at an annealing temperature of 1,000℃, where the highest value in the photoluminescence intensity was obtained. In addition to the red-shift of absorption edge, a higher annealing temperature caused the optical band gap energy of the SrWO₄:Sm³⁺ thin films to fall rapidly. These results suggest that the structural, morphological, and luminescent properties of SrWO₄:Sm³⁺ thin films can be controlled by varying annealing temperature.

• Journal of the Korean Ceramic Society
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• v.38 no.12
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• pp.1180-1186
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• 2001

W $O_3$-Sn $O_2$thin film sensors with approximately 1${\mu}{\textrm}{m}$ in thickness were fabricated by using a high-vacuum resistance-heating evaporator, were annealed at 50$0^{\circ}C$ for 4 hours in air, and then their crystallinities and surface microstructures were analyzed. As results of gas-sensing characteristics to oxidizing gas, N $O_2$, and reducing gas, CO, of 100 ppm, the highest gas sensitivities (S= $R_{gas}$/ $R_{air}$) were the W $O_3$thin-film sensor measured at 25$0^{\circ}C$ for N $O_2$(S≒1000) and the Sn $O_2$thin-film sensor measured at 15$0^{\circ}C$ to 25$0^{\circ}C$ range for CO (S≒0.25), respectively.ely.

• Journal of the Korean Ceramic Society
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• v.41 no.2
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• pp.97-101
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• 2004

W $O_{x}$-based semiconductor type thin film gas sensor was fabricated for the detection of N $O_{x}$ by reactive d.c. sputtering method. The relative oxidation state of the deposited W $O_{x}$ films was approximately compared by the calculation of the difference of the binding energy between Ols to W4 $f_{7}$2/ core level XPS spectra in the standard W $O_3$ powder of known composition. As the annealing temperature increased from 500 to 80$0^{\circ}C$, relative oxygen contents and grain size of the sputtered films were gradually increased. As the results of sensitivity ( $R_{gas}$/ $R_{air}$) measurements for the 5 ppm N $O_2$ gas, the sensitivity was 110 and the sensor showed recovery time as fast as 200 s. The other sensor properties were examined in terms of surface microstructure, annealing temperature, and relative oxygen contents. These results indicated that the W $O_3$ thin film with well controlled structure is a good candidate for monitoring and controlling of automobile exhaust.haust.t.t.t.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.187-189
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• 1995

A Surface Acoustic Wave Gas sensor for NO, CO, H$_2$gas detection was designed fabricated, and tested. A delay line device was designed to composite a single mode SAW oscillator which enables to measure a SAW velocity. To reduce the effect of temperature and humidity, dual delay line oscillator circuit was used. And final output was measured by digital frequency counter. NO, CO, H$_2$gas were detected by WO$_3$thin film deposited on the path of the Delay Line.

• Solar Energy
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• v.19 no.1
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• pp.1-8
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• 1999

Electrochromic $WO_3$ thin films were prepared by electron beam deposition. The transmission and durability of films were investigated. Coloring and bleaching experiments were repeated in an electrolyte of propylene carbonate with 0.6M of $LiClO_4$ by cyclic voltammetry. Spectrophotometer was used to measure the transmission in the degraded films. The 5000 ${\AA}$ thick film was found to be the stable after repeated cycles. The durability of the annealed film also showed improvements over unannealed samples. Tungsten oxide films with titanium content of about $10{\sim}15$ mol% was found to be most stable, undergoing the least degradation during the repeated cycles.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.295-298
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• 1996

In this study, we have fabricated all solid state electrochromic devices using WO$_3$ film as the working electrode, V$_2$O$\_$5/ film as the counter electrode and PEO-LiClO$_4$-PC film as the solid electrolyte. The WO$_3$ thin films for working electrode and V$_2$O$\_$5/ thin films for counter electrode were deposited onto ITO glass by vacuum evaporation and were shown good electrochromic and state properties after 1x10$\^$5/ cycles. PEO-LiClO$_4$-PC polymer electrolyte can easily be formed into thin films, do not absorb in the visible region of the light. Therefore, such electrolyte have electrochromic properties suitable for large-scale all solid-state electrochromic devices. All solid-staeelectrochromic devices fabricated in this polymer electrolyte have optical modulation of 20%∼30% at 1.5 V.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1308-1310
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• 1994

The electrochromism of $WO_3$ and $V_2O_5$ thin films have been studied. The $WO_3$ thin film is found to be cathodic coloration material and the coloration efficiency of this film is close to $60 [cm^2/C]$ in the near infrared region. The $V_2O_5$ thin film exhibits cathodic coloration in tile near infrared and anodic coloration in the blue and near UV region. The cathodic coloration in the $450{\sim}1100 nm$ wavelength range is relatively weak with a maximum coloration efficiency of $6 [cm^2/C]$).