• 한국전기전자재료학회논문지
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• 제30권4호
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• pp.229-234
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• 2017

In this study, we fabricated a TFT gas sensor with ZnO nanorods grown by hydrothermal synthesis. The suggested devices were compared with the conventional ZnO film-type TFTs in terms of the gas-response properties and the electrical transfer characteristics. The ZnO seed layer is formed by atomic-layer deposition (ALD), and the precursors for the nanorods are zinc nitrate hexahydrate ($Zn(NO_3)_2{\cdot}6H_2O$) and hexamethylenetetramine ($(CH_2)6N_4$). When 15 ppm of NO gas was supplied in a gas chamber at $150^{\circ}C$ to analyze the sensing capability of the suggested devices, the sensitivity (S) was 4.5, showing that the nanorod-type devices respond sensitively to the external environment. These results can be explained by X-ray photoelectron spectroscopy (XPS) analysis, which showed that the oxygen deficiency of ZnO nanorods is higher than that of ZnO film, and confirms that the ZnO nanorod-type TFTs are advantageous for the fabrication of high-performance gas sensors.

• 한국식품과학회지
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• 제34권6호
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• pp.947-953
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• 2002

시중에서 판매되는 김을 구입하여 습도가 32%, 43%, 75%, 온도는 $5^{\circ}C,\;15^{\circ}C,\;30^{\circ}C$에서 각각 김을 보관 한 후 저장 기간에 따른 김의 품질변화를 metal oxide 센서로 구성된 전자코와 SAW 센서를 바탕으로한 GC(z-Nose)를 이용하여 측정하였다. PCA 분석결과, $5^{\circ}C$, 32%에서 보관한 김의 경우는 저장기간이 지나도 김의 품질변화가 거의 없었다. 이것은 온도와 습도가 모두 낮아 김의 품질변화에는 영향을 미치지 않았으며, RH 43%, RH 75%에서 보관한 김의 경우는 저장기간이 지날수록 제 1 주성분 값이 양의 값$(+0.2{\sim}0.4})$에서 음의 값$(-0.4{\sim}\;-0.2)$으로 변화하는 경향으로 나타났다. RH 43% 보다 75%의 경우가 더 뚜렷한 감소를 보였으며 높은 상대습도 조건에서는 $15^{\circ}C$와 $30^{\circ}C$에서 유사한 경향을 나타내었다. z-Nose로 얻은 데이터를 패턴 분석한 결과 저장 기간이 지나면서 저장 온도와 습도에 따라 변질된 향시성분의 차이를 보여주었다. 이것은 미생물 수를 측정할 때와 마찬가지의 결과$(r^2=0.87)$를 보였으며 색도와는 크게 영향이 없음을 알 수 있었다. 이것으로 보면 전자코를 이용하여 조건을 달리하여 보관한 김의 품질관리를 효과적임을 알 수 있었다.

• 센서학회지
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• 제28권3호
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• pp.139-145
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• 2019

Precautionary detection of chemical warfare agents (CWAs) has been an important global issue mainly owing to their toxicity. To achieve proper detection, many studies have been conducted to develop sensitive gas sensors for CWAs. In particular, metal-oxide semi-conductors (MOS) have been investigated as promising sensing materials owing to their abundance in nature and excellent sensitivity. In this review, we mainly focus on various MOS-based gas sensors that have been fabricated for the detection of two specific CWA simulants, 2-chloroethyl ethyl sulfide (2-CEES) and dimethyl methyl phosphonate (DMMP), which are simulants of sulfur mustard and sarin, respectively. In the case of 2-CEES, we mainly discuss $CdSnO_3-$ and ZnO-based sensors and their reaction mechanisms. In addition, a method to improve the selectivity of ZnO-based sensors is mentioned. Various sensors and their sensing mechanisms have been introduced for the detection of DMMP. As the reaction with DMMP may directly affect the sensing properties of MOS, this paper includes previous studies on its poisoning effect. Finally, promising sensing materials for both gases are proposed.

• 센서학회지
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• 제17권4호
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• pp.281-288
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• 2008

Polyacrylonitrile(PAN)/metal oxide(MO) nanocomposite mats with a thickness of 0.12 mm were electrospun by adding 0 to 10 wt% of MO nanoparticles ($Fe_2O_3$, ZnO, $SnO_2$, $Sb_2O_3-SnO_2$) into PAN. Pt electrode was patterned on $Al_2O_3$ substrate by DC sputtering and then the PAN(/MO) mats on the Pt patterned $Al_2O_3$ were electrically wired to investigate the $CO_2$ gas sensing properties. As the MO content rose, the fiber diameter decreased due to the presence of lumps caused by the presence of MOs in the fiber. The PAN/2% ZnO mat revealed a faster response time of 93 s and a relatively short recovery of 54 s with a ${\Delta}R$ of 0.031 M${\Omega}$ at a $CO_2$ concentration of 200 ppm. The difference in sensitivity was not observed significantly for the PAN/MO fiber mats in the $CO_2$ concentration range of 100 to 500 ppm. It can be concluded that an appropriate amount of MO nanoparticles in the PAN backbone leads to improvement of the $CO_2$ gas sensing properties.

• 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.

• 센서학회지
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• 제10권2호
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• pp.108-117
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• 2001

폭발성 및 가연성 가스의 종류 및 그 정량화론 위한 10개의 개별 센서가 하나의 기판 위에 집적시킨 센서 어레이를 개발하였다. 이 센서어레이는 여러 가지 가연성 가스(부탄, 메탄, 프로판, 일산화탄소, LPG)에 대해서 차별화 된 감도 패턴을 가지도록, 나노 사이즈의 grain를 가지는 $SnO_2$를 모 물질로 하는 10개의 서로 다근 감지 물질로 구성하였고, 센서어레이 전반에서 균일한 온도 분포가 되도록 히터를 기판에 내장시켰다. $400^{\circ}C$에서 동작하는 어레이상의 센서들은 저농도에서도 고감도와 재현성의 특성을 보여 주었다. 이들 감도패턴을 이용하여, 주성분 분석 기법을 통해 환경기준치(LEL, TLV) 범위에서 부탄, 프로판, 메탄, LPG의 폭발성 및 가연성 가스의 종류 인식 및 정량화 할 수 있었다. 그리고, 주성분 분석 기법으로 치적 센서 개수 선정에 응용하였다.

• 센서학회지
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• 제16권1호
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• pp.11-16
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• 2007

CuO is an important transition metal oxide with many practical applications such as catalysts, p-type semiconductor, solar cells, magnetic storage media and cathode materials. In this contribution, nanocrystalline CuO powders were prepared by solution reduction method using copper chloride ($CuCl_{2}{\cdot}2H_{2}O$), hydrazine ($N_{2}H_{4}$) and NaOH and subsequent heat treatment. The gas sensor using nanocrystalline CuO powders showed high sensitivities to acetone and ethanol.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.602-605
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• 2000

Recently, a study of intellectual smell recognition system is applied for the various fields such as control of food processing and survey of decay. A basic gas recognition system was implemented gases using four metal oxides semiconductor sensors as inputs. A CPLD chip of twenty thousand gates level was used for this purpose. The CPLD chip was designed and the availability of the one chip smell recognition system was tested.

• 한국재료학회지
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• 제6권7호
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• pp.716-722
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• 1996

박막 형 가스 센서의 막 두께가 가스 감지 특성에 미치는 영향을 단순화된 모델로부터 수식으로 유도하여 해석하였고, 그것을 ${SnO}_{2}$와 CuO-${SnO}_{2}$ 박막의 ${H}_{2}S$ 감응 특성에 대한 실험 결과에 적용하였다. 유도된 수식으로부터 박막 가스 센서의 가스 감지 특성은 가스의 박막 안으로의 확산성에 크게 의존하며, 그 가스 확산성은 박막의 두께, 가스의 센서 재료의 반응성, 작동 온도 등에 의해서 결정됨을 알 수 있었다. 또한 이 수식은 CuO-${SnO}_{2}$ 박막의 ${H}_{2}S$ 감응 특성에 대한 실험 결과와 비교적 잘 일치하였고, CuO-${SnO}_{2}$ 박막과 ${SnO}_{2}$ 박막의 서로 판이한 ${H}_{2}S$ 감응 특성에 대한 설명에 적용되었다. 이로부터, 일반적인 산화물 반도체식 가스 센서의 가스 감지 특성이 가스 확산성에 의해서 어떻게 지배되는가를 구체적으로 제안하였다.

• Transactions on Electrical and Electronic Materials
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• 제14권4호
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• pp.216-220
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• 2013

The etching characteristics of indium zinc oxide (IZO) in $Cl_2/Ar$ plasma were investigated, including the etch rate and selectivity of IZO. The IZO etch rate showed non-monotonic behavior with increasing $Cl_2$ fraction in the $Cl_2/Ar$ plasma, and with increasing source power, bias power, and process pressure. In the $Cl_2/Ar$ (75:25%) gas mixture, a maximum IZO etch rate of 87.6 nm/min and etch selectivity of 1.09 for IZO to $SiO_2$ were obtained. Owing to the relatively low volatility of the by-products formation, ion bombardment was required, in addition to physical sputtering, to obtain high IZO etch rates. The chemical state of the etched surfaces was investigated with X-ray photoelectron spectroscopy. These data suggested that the IZO etch mechanism was ion-enhanced chemical etching.