• 한국응용과학기술학회지
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• 제34권2호
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• pp.410-417
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• 2017

저장조건에 따른 금산 추부깻잎의 물리적 특성을 분석하였다. 깻잎의 a/b값은 저장기간이 증가할수록 증가하는 경향을 보였다. 저장온도 $25^{\circ}C$와 $4^{\circ}C$에서 제 1주성분 값의 기여율은 각각 93.07%, 97.81%로 나타나 전자코를 이용한 저장온도에 따른 휘발성 향기성분 패턴의 구별이 가능하였다. 저장기간에 따른 제 1주성분 값의 변화는 저장온도 $25^{\circ}C$에 비해 $4^{\circ}C$에서 변화의 폭이 적었음을 확인할 수 있었다.

• 센서학회지
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• 제13권3호
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• pp.188-194
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• 2004

With a remarkable advance in CMOS (complimentary metal-oxide-semiconductor) process technology, a variety of vision sensors with signal processing circuits for complicated functions are actively being developed. Especially, as the principles of signal processing in human retina have been revealed, a series of vision chips imitating human retina have been reported. Human retina is able to detect the edge and motion of an object effectively. The edge detection among the several functions of the retina is accomplished by the cells called photoreceptor, horizontal cell and bipolar cell. We designed a CMOS vision chip by modeling cells of the retina as hardwares involved in edge and motion detection. The designed vision chip was fabricated using $0.6{\mu}m$ CMOS process and the characteristics were measured. Having reliable output characteristics, this chip can be used at the input stage for many applications, like targe tracking system, fingerprint recognition system, human-friendly robot system and etc.

• 한국식품과학회지
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• 제35권4호
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• pp.648-652
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• 2003

본 실험은 순수참기름과 혼합참기름의 구별 및 순도판별을 용이하게 하기 위한 분석방법을 제시하고자 실행되었다. 순수참기름과 옥수수기름을 95 : 5, 90 : 10, 80 : 20(w/w)의 비율로 각각 비율을 달리해서 혼합참기름을 제조한 후 GC, SPME-GC/MS, 전자코를 이용한 분석을 실시하였다. 지방산조성(mole%)을 비교한 결과 옥수수기름이 10%이상 함유된 혼합참기름과 순수참기름 간에는 stearic acid와 linoleic acid의 함량의 변화로 구별이 가능하였으나 5%내로 옥수수유가 함유된 혼합참기름과 순수참기름과의 구별은 용이하지 않았다. 향기성분동정을 위해 SPME-GC/MS 분석을 실시한 결과순수참기름과 혼합참기름은 같은 향기성분 패턴을 보여 구별하기 어려웠다. 반면, MOS 유형의 전자코를 이용하여 향기성분패턴 분석결과 제1주성분 값의 기여율이 98.76%로 구별이 가능하였으며 이로써 신속하고 편리하게 비파괴적 분석 방법인 전자코를 활용하여 순수참기름과 혼합참기름을 구별할 수 있었다.

• Current Optics and Photonics
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• 제7권5호
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• pp.485-495
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• 2023

The pixel size in high-resolution complementary metal-oxide-semiconductor (CMOS) image sensors continues to shrink due to chip size limitations. However, the pixel pitch's miniaturization causes deterioration of optical performance. As one solution, a quad color filter (CF) array with pixel binning has been developed to enhance sensitivity. For high sensitivity, the microlens structure also needs to be optimized as the CF arrays change. In this paper, the covered microlens, which consist of four microlenses covered by one large microlens, are proposed for the quad CF array in the backside illumination pixel structure. To evaluate the optical performance, the suggested microlens structure was simulated from 0.5 ㎛ to 1.0 ㎛ pixels at the center and edge of the sensors. Moreover, all pixel structures were compared with and without in-pixel deep trench isolation (DTI), which works to distribute incident light uniformly into each photodiode. The suggested structure was evaluated with an optical simulation using the finite-difference time-domain method for numerical analysis of the optical characteristics. Compared to the conventional microlens, the suggested microlens show 29.1% and 33.9% maximum enhancement of sensitivity at the center and edge of the sensor, respectively. Therefore, the covered microlens demonstrated the highly sensitive image sensor with a quad CF array.

• 한국재료학회지
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• 제34권5호
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• pp.235-241
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• 2024

Gas identification techniques using pattern recognition methods were developed from four micro-electronic gas sensors for noxious gas mixture analysis. The target gases for the air quality monitoring inside vehicles were two exhaust gases, carbon monoxide (CO) and nitrogen oxides (NO_x), and two odor gases, ammonia (NH₃) and formaldehyde (HCHO). Four MEMS gas sensors with sensing materials of Pd-SnO₂ for CO, In₂O₃ for NO_X, Ru-WO₃ for NH₃, and hybridized SnO₂-ZnO material for HCHO were fabricated. In six binary mixed gas systems with oxidizing and reducing gases, the gas sensing behaviors and the sensor responses of these methods were examined for the discrimination of gas species. The gas sensitivity data was extracted and their patterns were determined using principal component analysis (PCA) techniques. The PCA plot results showed good separation among the mixed gas systems, suggesting that the gas mixture tests for noxious gases and their mixtures could be well classified and discriminated changes.

• 센서학회지
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• 제23권5호
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• pp.337-341
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• 2014

For various additives doped-$VO_2$ critical temperature sensors using the nature of semiconductor to metal transition, the crystallinity, microstructure, and temperature vs. resistance characteristics were systematically investigated. As a starting material of $VO_2$ sensor, vanadium pentoxide ($V_2O_5$) powders were used, and CaO, SrO, $Bi_2O_3$, $TiO_2$, and PbO dopants were used, respectively. The $V_2O_5$ powders with dopants were mixed with a vehicle to form paste. This paste was silk screen-printed on $Al_2O_3$ substrates and then $V_2O_5$-based thick films were heat-treated at $500^{\circ}C$ for 2 hours in $N_2$ gas atmosphere for the reduction to $VO_2$. From X-ray diffraction analysis, $VO_2$ phases for pure $VO_2$, and CaO and SrO-doped $VO_2$ thick films were confirmed and their grain sizes were 0.57 to $0.59{\mu}m$. The on/off resistance ratio of the $VO_2$ sensor in phase transition temperature range was $5.3{\times}10^3$ and that of the 0.5 wt.% CaO-doped $VO_2$ sensor was $5.46{\times}10^3$. The presented critical temperature sensors could be commercialized for fire-protection and control systems.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.16.1-16.1
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• 2011

$TiO_2$ is a promising material for gas sensors. To achieve high sensitivities, the material should exhibit a large surface-to-volume ratio and possess the high accessibility of the gas molecules to the surface. Accordingly, a wide variety of porous $TiO_2$ nanomaterials synthesized by wet-chemical methods have been reported for gas sensor applications. Nonetheless, achieving the large-area uniformity and comparability with well-established semiconductor production processes of the methods is still challenging. An alternative method is soft-templating which utilizes nanostructured inorganic or organic materials as sacrificial templates for the preparation of porous materials. Fabrication of macroporous $TiO_2$ films and hollow $TiO_2$ tubes by soft-templating and their gas sensing applications have been reported recently. In these porous materials composed of assemblies of individual micro/nanostructures, the form of links or necks between individual micro/nanostructures is a critical factor to determine gas sensing properties of the material. However, a systematic study to clarify the role of links between individual micro/nanostructures in gas sensing properties of a porous metal oxide matrix is thoroughly lacking. In this work, we have demonstrated a fabrication method to prepare highly-ordered, embossed $TiO_2$ films composed of anatase $TiO_2$ hollow hemispheres via soft-templating using polystyrene beads. The form of links between hollow hemispheres could be controlled by $O_2$ plasma etching on the bead templates. This approach reveals the strong correlation of gas sensitivity with the form of the links. Our experimental results highlight that not only the surface-to-volume ratio of an ensemble material composed of individual micro/nanostructures but also the links between individual micro/nanostructures play a critical role in evaluating the sensing properties of the material. In addition to this general finding, the facileness, large-scale productivity, and compatability with semiconductor production process of the proposed fabrication method promise applications of the embossed $TiO_2$ films to high-quality sensors.

• 센서학회지
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• 제23권1호
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• pp.15-18
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• 2014

We present gas sensing performance based on $2{\times}2$ sensor array with four different elements ($TiO_2$, $SnO_2$, $WO_3$ and $In_2O_3$ thin films) fabricated by rf sputter. Each thin film was deposited onto the selected $SiO_2$/Si substrate with Pt interdigitated electrodes (IDEs) of $5{\mu}m$ spacing which were fabricated on a $SiO_2$/Si substrate using photolithography and dry etching. For 5 ppm $NO_2$ and 50 ppm CO, each thin film sensor has a different response to offers the distinguishable response pattern for different gas molecules. Compared with the conventional micro-fabrication technology, $2{\times}2$ sensor array with such remarkable response pattern will be open a new foundation for monolithic integration of high-performance chemoresistive sensors with simplicity in fabrication, low cost, high reliablity, and multifunctional smart sensors for environmental monitoring.

• 한국전기전자재료학회논문지
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• 제27권6호
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• pp.394-398
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• 2014

We fabricated the electrolyte-dielectric-metal (EDM) sensor on the base of AAO (anodic aluminum oxide) template with variation of the anodizing temperature. When a surface is immersed or created in an aqueous solution, a discontinuity is formed at the interface where such physicochemical variables as electrical potential and electrolyte concentration change significantly from the aqueous phase to another phase. Because of the different chemical potentials between the two phases, charge separation often occurs at the interfacial region [1]. This interfacial region, togeter with the charged surface, is usually known as the electrical double layer (EDL) [2]. The structural and electrochemical properties of AAO sensor were investigated for applications in capacitive pH sensors. To change the thickness of the AAO template, the anodizing temperature was varied from $5^{\circ}C$ to $20^{\circ}C$, the thickness of the AAO template invreased from 300 nm to 477 nm. The pH sensitivity of sensors with the anodizing temperature of $20^{\circ}C$ showed the highest value of 56.4 mV/pH in the pH range of 3 to 11. The EDM sensor with the anodizing temperature of $20^{\circ}C$ exhibited the best long-term stability of 0.037 mV/h.

• 센서학회지
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• 제20권3호
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• pp.156-161
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• 2011

We fabricated a schottky barrier metal oxide semiconductor field effect transistor(SB-MOSFET) by applying indium-tin-oxide(ITO) to the source/drain on a highly resistive GaN layer grown on a silicon substrate. The MOSFET, with 10 ${\mu}M$ gate length and 100 ${\mu}M$ gate width, exhibits a threshold gate voltage of 2.7 V, and has a sub-threshold slope of 240 mV/dec taken from the $I_{DS}-V_{GS}$ characteristics at a low drain voltage of 0.05 V. The maximum drain current is 18 mA/mm and the maximum transconductance is 6 mS/mm at $V_{DS}$=3 V. We observed that the spectral photo-response characterization exhibits that the cutoff wavelength was 365 nm, and the UV/visible rejection ratio was about 130 at $V_{DS}$ = 5 V. The MOSFET-type UV detector using ITO, has a high UV photo-responsivity and so is highly applicable to the UV image sensors.