• JSTS:Journal of Semiconductor Technology and Science
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• 제2권2호
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• pp.93-101
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• 2002

We have proposed and fabricated two lateral type field emission diodes, poly-Si emitter by utilizing the local oxidation of silicon (LOCOS) and GaN emitter using metal organic chemical vapor deposition (MOCVD) process. The fabricated poly-Si diode exhibited excellent electrical characteristics such as a very low turn-on voltage of 2 V and a high emission current of $300{\;}\bu\textrm{A}/tip$ at the anode-to-cathode voltage of 25 V. These superior field emission characteristics was speculated as a result of strong surface modification inducing a quasi-negative electron affinity and the increase of emitting sites due to local sharp protrusions by an appropriate activation treatment. In respect, two kinds of procedures were proposed for the fabrication of the lateral type GaN emitter: a selective etching method with electron cyclotron resonance-reactive ion etching (ECR-RIE) or a simple selective growth by utilizing $Si_3N_4$ film as a masking layer. The fabricated device using the ECR-RIE exhibited electrical characteristics such as a turn-on voltage of 35 V for $7\bu\textrm{m}$ gap and an emission current of~580 nA/l0tips at anode-to-cathode voltage of 100 V. These new field emission characteristics of GaN tips are believed to be due to a low electron affinity as well as the shorter inter-electrode distance. Compared to lateral type GaN field emission diode using ECR-RIE, re-grown GaN emitters shows sharper shape tips and shorter inter-electrode distance.

• 한국전기전자재료학회논문지
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• 제17권8호
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• pp.823-829
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• 2004

In this paper, non-self-aligned SiGe HBTs with ${f}_\tau$ and${f}_max $above 50 GHz have been fabricated using an RPCVD(Reduced Pressure Chemical Vapor Deposition) system for wireless applications. In the proposed structure, in-situ boron doped selective epitaxial growth(BDSEG) and TiSi$_2$ were used for the base electrode to reduce base resistance and in-situ phosphorus doped polysilicon was used for the emitter electrode to reduce emitter resistance. SiGe base profiles and collector design methodology to increase ${f}_\tau$ and${f}_max $ are discussed in detail. Two SiGe HBTs with the collector-emitter breakdown voltages ${BV}_CEO$ of 3 V and 6 V were fabricated using SIC(selective ion-implanted collector) implantation. Fabricated SiGe HBTs have a current gain of 265 ∼ 285 and Early voltage of 102 ∼ 120 V, respectively. For the $1\times{8}_\mu{m}^2$ emitter, a SiGe HBT with ${BV}_CEO$= 6 V shows a cut-off frequency, ${f}_\tau$of 24.3 GHz and a maximum oscillation frequency, ${f}_max $of 47.6 GHz at $I_c$of 3.7 mA and$V_CE$ of 4 V. A SiGe HBT with ${BV}_CEO$ = 3 V shows ${f}_\tau$of 50.8 GHz and ${f}_max $ of 52.2 GHz at $I_c$ of 14.7 mA and $V_CE$ of 2 V.

• Bulletin of the Korean Chemical Society
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• 제26권1호
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• pp.38-42
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• 2005

Bis(2-methylbenzaldehyde)butane-2,3-dihydrazone(TDSB) was used as new N-N Schiff's base which plays the role of an excellent ion carrier in the construction of a La(III) membrane sensor. The best performance was obtained with a membrane containing, 30% poly(vinyl chloride), 60% benzyl acetate, 6% TDSB and 4% sodium tetraphenyl borate. This sensor reveals a very good selectivity towards La(III) ions over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. The proposed electrode exhibits a Nernstian behavior (with slope of 19.8 mV per decade) over a wide concentration range (1.0 ${\times}$ 10$^{-5}$-1.0 ${\times}$ 10$^{-1}$ M). The detection limit of the sensor is 7.0 ${\times}$ 10$^{-6}$ M. It has a very short response time, in the whole concentration range ($\sim$5 s), and can be used for at least twelve weeks in the pH range of 3.0-9.4. The proposed sensor was successfully applied as an indicator electrode for the potentiometric titration of a La(III) solution, with EDTA. It was also successfully applied in the determination of fluoride ions in three mouth wash preparations.

• 대한화학회지
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• 제44권2호
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• pp.115-119
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• 2000

새로운 캘릭스[4] 크라운 화합물을 이온 선택성 물질로 사용하고 지지체로 PVC(poly(vinylchloride)), 가소제로 DOS(Dioctyl sebacate}를 사용하여 막전극을 제작 하였다. 제작한 막전극을 지시전극으로 사용하여 알칼리, 알칼리토금속 이온 그리고 전이금속 이온에 대하여 각각의 감응전위를 측정한 결과, $10^{-6}{\sim}10^{-2}M\;Pb(NO_3)_2$ 용액에서 $Pb^{2+}$이온의 감응전위가 이론적인 Nernstian식 기울기에 가까운 27.0 mV/decade로 직선성이 잘 성립하는 감응전위를 나타내었다. $Pb^{2+}$ 이온 농도변화에 따른 막의 감응시간은 $t_{90}$=10 sec 이었고, 막의 사용기간은 2개월 정도이다. 또한 pH 영향을 조사해 본 결과 pH $2.0{\sim}12$ 범위에서 감응전위 값이 일정하게 유지되었다.

• Journal of Biosystems Engineering
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• 제36권2호
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• pp.96-108
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• 2011

Several methods of in-field measurements of Nitrogen and other soil properties using cores extracted by a hydraulic soil sampler were evaluated. A prototype core scanner was built to accommodate Veris Technologies commercial Vis-NIRS equipment. The testing result for pH, P and Mg were close to RPD (Ratio of Prediction to Deviation = Standard deviation/RMSE) of 2, however the scanner could not achieve the goal of RPD of 2 on some other properties, especially on nitrate nitrogen ($NO_3$) and potassium (K). In situ NIRS/EC probe showed similar results to the core scanner; pH, P and Mg were close to RPD of 2, while $NO_3$ and K were RPD of 1.5 and 1.2, respectively. Correlations between estimations using the probe and the core scanner were strong, with $r^2$ > 0.7 for P, Mg, Total N, Total C and CEC. Preliminary results for mid-IR spectroscopy showed an $r^2$ of 0.068 and an RMSE for nitrate (N) of 18 ppm, even after the removal of calcareous samples and possible N outlier. After removal of calcareous samples on a larger sample set, results improved considerably with an $r^2$ of 0.64 and RMSE of 6 ppm. However, this was only possible after carbonate samples were detected and eliminated, which would not be feasible under in-field measurements. Testing of $NO_3$ and K ion-selective electrodes (ISEs) revealed promising results, with acceptable errors measuring soil solutions containing nitrate and potassium levels that are typical of production agriculture fields.

• 전기학회논문지
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• 제59권1호
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• pp.130-133
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• 2010

Although many structures based on $SnO_2$ nanowires have been demonstrated, there is a limitation towards practical application due to the unwanted contact potential between the metal electrode and the $SnO_2$ nanowire. This is mostly due to the presence of the native oxide layer that acts as an insulator between the metal contact and the nanowire. In this study the contact properties between Ti/Au contacts and a single $SnO_2$ nanowire was compared to the electrical properties of a contact without the oxide layer. RIE(Reactive Ion Etching) is used to selectively remove the oxide layer from the contact area. The $SnO_2$ nanowires were synthesized by chemical vapor deposition (CVD) and dispersed on a $Si/Si_3N_4$ substrate. The Ti/Au (20nm/100nm) electrodes were formed bye-beam lithography, e-beam evaporation and a lift-off process.

• Fisheries and Aquatic Sciences
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• 제15권3호
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• pp.203-207
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• 2012

The amount of fluoride removed from Antarctic krill via organic acid extraction depends on the extraction time, concentration, extraction volume, and the nature of the acid itself. The fluoride content in Euphausia superba was determined by measuring the concentration of fluoride ion in acidic extracts using an ion-selective electrode. The best results were obtained by adding 50 mL of 0.01 M citric acid to 0.3-0.5 g of krill and extracting for 5 min. Under these conditions, recoveries of fluoride from frozen whole krill and krill meat were 95.6-99.5% and 97.5-101.3%, respectively. The dry basis fluoride contents of krill by-product, krill meat and the boiled krill were 705, 298, and 575 ppm, respectively. These levels were significantly reduced by citric acid extraction.

• Food Science and Biotechnology
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• 제14권4호
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• pp.554-557
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• 2005

As a device for taste sensation, an 8-channel taste evaluation system was prepared and applied for discriminant analysis of marketed liquor. The biomimetic polymer membranes for the system were prepared through a casting procedure by employing polyvinyl chloride, bis (2-ethylhexyl)sebacate as plasticizer and electroactive materials such as valinomycin in the ratio of 33:66:1, and were separately attached over the sensitive area of ion-selective electrodes to construct the corresponding taste sensor array. The sensor array in conjunction with a double junction reference electrode was connected to a high-input impedance amplifier and the amplified sensor signals were interfaced to a personal computer via an A/D converter. When the signal data from the sensor array for 3 groups of marketed liquor like Maesilju, Soju and beer were analyzed by principal component analysis after normalization, it was observed that the 1st, 2nd and 3rd principal component were responsible for most of the total data variance, and the analyzed liquor samples were discriminated well in 2 dimensional principal component planes composed of the 1st-2nd and the 1st-3rd principal component.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.602-604
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• 2004

A portable electronic tongue(E-Tongue) system using an array of ion-selective electrode(ISE) and personal digital assistants(PDA) for recognizing and analyzing food and drink have been designed. By the employment of PDA, the complex algorithm such as fuzzy c-means algorithm(FCMA) could be used in E-Tongue, FCMA could iteratively solve the cluster centers of pre-determined standard patterns. And the membership between the standard patterns and unknown pattern could be analyzed easily by the present E-Tongue combined with PDA.

• Carbon letters
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• 제4권2호
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• pp.64-68
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• 2003

A study on the electrosorption of uranium ions onto a porous activated carbon fiber (ACF) was performed to treat uraniumcontaining lagoon sludge. The result of the continuous flow-through cell electrosorption experiments showed that the applied negative potential increased the adsorption kinetics and capacity in comparison to the open-circuit potential (OCP) adsorption for uranium ions. Effective U(VI) removal is accomplished when a negative potential is applied to the activated carbon fiber (ACF) electrode. For a feed concentration of 100 mg/L, the concentration of U(VI) in the cell effluent is reduced to less than 1 mg/L. The selective removal of uranium ions from electrolyte was possible by the electrosorption process.