• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.185-185
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• 2011

ZnTe semiconductor is very attractive materials for optoelectronic devices in the visible green spectral region because of it has direct bandgap of 2.26 eV. The prototypes of ZnTe light emitting diodes (LEDs) have been reported [1], showing that their green emission peak closely matches the most sensitive region of the human eye. Another application to photovoltaics proved that ZnTe is useful for the production of high-efficiency multi-junction solar cells [2,3]. By using the pulse laser deposition system, ZnTe thin films were deposited on ZnO thin layer, which is grown on (0001) Al2O3substrates. To produce the plasma plume from an ablated ZnO and ZnTe target, a pulsed (10 Hz) YGA:Nd laser with energy density of 95 mJ/$cm^2$ and wavelength of 266 nm by a nonlinear fourth harmonic generator was used. The laser spot focused on the surface of the ZnO and ZnTe target by using an optical lens was approximately 1 mm2. The base pressure of the chamber was kept at a pressure around $10^{-6}$ Torr by using a turbo molecular pump. The oxygen gas flow was controlled around 3 sccm by using a mass flow controller system. During the ZnTe deposition, the substrate temperature was $400^{\circ}C$ and the ambient gas pressure was $10^{-2}$ Torr. The structural properties of the samples were analyzed by XRD measurement. The optical properties were investigated by using the photoluminescence spectra obtained with a 325 nm wavelength He-Cd laser. The film surface and carrier concentration were analyzed by an atomic force microscope and Hall measurement system.

• Korean Journal of Materials Research
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• v.7 no.1
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• pp.21-26
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• 1997

고주파 마그네트론 반응성 스퍼터링(rf magnetron reactive sputtering)으로 티타늄산화물 박막을 제조하여 산소비율에 따른 반응성 스퍼터링의 증착기구를 조사하고 산소비율 및 기판온도에 따른 산화물 조성의 변화, 미세조직, 광학적 특성의 변화를 연구하였다. 기존의 진공기상증착법으로 증착만 박막에 비해, 금속타겟을 사용하여 높은 증착속도를 얻을 수 있는 반응성 마그네트론 스퍼터링으로 성막한 티타늄산화물 박막은 치밀도가 우수하여 높은 굴절률(2.06)과 높은 광투과율을 보였다. 상온에서 성막된 티타늄 산화물박막의 경우, 산소비율이 낮은 조건에서는 다결정형의조직을 보였으나 산소비율이 높은 경우에는 비정질조직을 나타냈으며, 기판온도가 30$0^{\circ}C$ 이상에서는 산소비율에 상관없이 다결정형의 조직을 나타냈다. 하지만 산소비율이 임계값이상에서는 박막의 조성, 증착속도 등이 거의 변하지 않는 안정된 증착조건을 보였다. 30% 이상의 산소비율의 반응성 스퍼터링의 조건에서는 TiO$_{2}$의 조성의 박막으로 성장하여 약 3.82-3.87 eV의 band gap을 나타냈으며 기판온도의 증가에 따라 비정질 TiO$_{2}$에서 다결정 TiO$_{2}$으로 조직의 변화를 보여 광투과도도 약간 증가하는 경향을 나타냈다.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.6
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• pp.369-374
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• 2005

Nitrogen ion implantation in Nimonic 80A using plasma immersion ion implantation (PIII) was investigated at a pulse voltage of -60 kV and ion dose of $3{\times}10^{17}{\sharp}/cm^2$, $6{\times}10^{17}{\sharp}/cm^2$, $12{\times}10^{17}{\sharp}/cm^2$. PIII is an effective technology to improve the surface hardness and wear resistance of materials. And also this technology is not limited by the shape and size of materials. PIII would be a promising technique in the future. Surface hardness and wear resistance of the $N^+$ ion implanted Nimonic 80A were increased with the increase in the incident ion dose. The surface hardness of the untreated Nimonic 80A is 420 Hv, the hardness of implanted Nimonic 80A is 1050 Hv at $N^+$ ion dose of $12{\times}10^{17}{\sharp}/cm^2$. The wear loss of the untreated is 82.5 mg, the wear loss of the implanted is 0.004g at $N^+$ ion dose of $12{\times}10^{17}{\sharp}/cm^2$. The $Cr_2N$ is detected on the surface of the implanted Nimonic 80A by XRD analysis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.424-427
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• 2002

In this papaer, there is a basic research for the development of the Hybrid digital radiation detector with a new system, make up for existing digital radiation detector of direct/indirect method with a weak point. for enhance the efficiency characteristics of signal response from X-ray detector using the a-Se, We make sample with various kinds of layer, through the ratio of As(0.l%,0.3%,0.5%,1%,1.5%,5%,10%). We measure net charge with a leakage current and photo current for electric charateristics. Ratio of As in a-Se consist of 7 stage, It made of using the thermal deposition system, In the made of samples, we made multi layer using the EFIRON optical adhesives from phosphor layer consist of Oxybromide$(BrO_2)$. As a result of X-ray measurement, the best result is ; leakage current(0.30nA/cm2), net charge(610.13pC/cm2/mR) when the condition is voltage(9V/um), 0.3% ratio of As in multi layer(BrO2 + a-Se)

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.6
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• pp.1121-1126
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• 2010

Borosilicate glass (81% $SiO_2$-2% $Al_2O_3$-13% $B_2O_3$-4% $Na_2O_3$) was prepared, and the glass was ion exchanged in $KNO_3$ powder containing different temperature and time. The $K^+-Na^+$ ion exchange takes place at the glass surface and creates compressed stress, which raise the mechanical strength of the glass. The depth profile of $Na^+$ and $K^+$ was observed by electron probe micro analyzer. With the increasing heat-treatment time from 0min to 20min, the depth profile was increased from 17.1um to 29.4um, but mechanical properties were decreased. It was also found out that excessive heat treatment brings stress relaxation. The Vickers hardness, Fracture Toughness and bending strength of ion exchanged samples at $570^{\circ}C$ for 10min were $821.8H_v$, $1.3404MPa{\cdot}m^{1/2}$, and 953MPa, which is about 120%, 180%, and 450% higher than parent borosilicate glass, respectively. Transmittance was analyzed by UV-VIS-NIR spectrophotometer. Transmittance of ion exchanged borosilicate glass was decreased slightly at visible-range. It can be expected that transparent bulletproof materials in more light-weight and thinner by ion exchanged borosilicate glass.

• KSBB Journal
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• v.9 no.3
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• pp.319-324
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• 1994

A biosensor for the measurement of malate has been constructed by the sodium-alginate immobilized bundle sheath cell tissue of corn leaf containing malate dehydrogenase (decarboxylating) (EC 1. 1. 1. 40) on the CO2 gas-sensing electrode. The proposed tissue sensor had the linear in the range of malate concentration $5.5{\times}10^{-5}M∼2.5{\times}10^{-2}M$ with a slope of 53.5 mV/decade in 0.02M Tris-HCl buffer solution at optimum pH 8.0, and $25^{\circ}C$. A response time was 16∼18min. The present L-malate sensing tissue sensor is stable for more than one week. At pH 7.4, Km value was $0.6{\times}10^{-5}M$. The various kinds of salt did not effect the signal of malate tissue biosensor as the inhibitor. We can measure the malate by the CO2 electrode at the pH=8.0. Thus, the proposed tissue sensor will be useful for the measurement of malate.

• Journal of Microbiology
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• v.43 no.1
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• pp.21-27
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• 2005

A soluble Cr(VI) reductase was purified from the cytoplasm of Escherichia coli ATCC 33456. The molecular mass was estimated to be 84 and 42 kDa by gel filtration and SDS-polyacrylamide gel electrophoresis, respectively, indicating a dimeric structure. The pI was 4.66, and optimal enzyme activity was obtained at pH 6.5 and $37^{\circ}C$. The most stable condition existed at pH 7.0. The purified enzyme used both NADPH and NADH as electron donors for Cr(VI) reduction, while NADPH was the better, conferring 61% higher activity than NADH. The $K_m$ values for NADPH and NADH were determined to be 47.5 and 17.2 umol, and the $V_max$ values 322.2 and 130.7 umol Cr(VI) $min^{-1}mg^{-1}$ protein, respectively. The activity was strongly inhibited by N-ethylmalemide, $Ag^{2+},\;Cd^{2+},\;Hg^{2+}$, and $Zn^{2+}$. The antibody against the enzyme showed no immunological cross reaction with those of other Cr(VI) reducing strains.

• Journal of Sensor Science and Technology
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• v.14 no.2
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• pp.96-100
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• 2005

The planar Schottky diodes were fabricated and modeled to probe the device applicability of the cracked GaN epitaxial layer on a (111) silicon substrate. On the unintentionally n-doped GaN grown on silicon, we deposited Ti/Al/Ni/Au as the ohmic metal and Pt as the Schottky metal. The ohmic contact achieved a minimum contact resistivity of $5.51{\times}10.5{\Omega}{\cdot}cm^{2}$ after annealing in an $N_{2}$ ambient at $700^{\circ}C$ for 30 sec. The fabricated Schottky diode exhibited the barrier height of 0.7 eV and the ideality factor was 2.4, which are significantly lower than those parameters of crack free one. But in photoresponse measurement, the diode showed the peak responsivity of 0.097 A/W at 300 nm, the cutoff at 360 nm, and UV/visible rejection ratio of about $10^{2}$. The SPICE(Simulation Program with Integrated Circuit Emphasis) simulation with a proposed model, which was composed with one Pt/GaN diode and three parasitic diodes, showed good agreement with the experiment.

• Restorative Dentistry and Endodontics
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• v.20 no.2
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• pp.721-731
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• 1995

The purpose of this study was to evaluate the adaptability to tooth structure of light-cured glass ionomer cements. In this, study, class V cavities were prepared on the buccal surfaces of thirty extracted human premolar teeth, and they were randomly assigned into 3 groups with 10 teeth. The cavities of each groups were filled with the Fuji II LC(GC International Corp., Japan), Vitremer(3M Dental Products Division, U.S.A) and VariGlass VLC(Caulk/Dentsply Inc., U.S.A.). The specimens were immersed in 1% methylene blue solution and stored in 100% realtive humidity at $37^{\circ}C$ for 5 days. And then, the specimens sectioned buccolingually. Degree of eke penetration at tooth--restoration interfaces were examined by magnifying glass at occlusal and gingival margin. The results were as follows : 1. On the occlusal margin, among the experimental groups, the group 2 showed the lowest microleakage($1.40{\pm}1.17$) and the group 1 showed the highest microleakage($3.10{\pm}0.99$). There was significant difference between group 1 and group 2(P<0.01). 2. On the gingival margin, among the experimental groups, the group 2 showed the lowest microleakage($2.50{\pm}1.08$) and the group 1 showed the highest microleakage($3.50{\pm}0.84$). But there was not significant. difference among the experimental groups(P>0.05). 3. The degree of microleakage at occlusal margin was less than gingival margin in all experimental groups.

• Transactions of Materials Processing
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• v.27 no.6
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• pp.347-355
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• 2018

This study investigated the effects of the processing number of multi-axial diagonal forging (MADF) on the microstructural changes of OFC fabricated by MADF processes. The as-extruded OFC was cut to $25mm^3$ cube for the MADF processes. The MADF process consists of plane forging with a thickness reduction of 30% and diagonal forging with a diagonal forging angle of $135^{\circ}$. In order to analyze the microstructural evolutions according to the number of repetitions, 1, 2, 3 and 4 cycles of the MADF process were performed. OFC specimens were successfully deformed without surface cracking for up to 4 cycles of MADF. The grain size, average misorientation and average grain orientation spread (GOS) of MADF processed materials were analyzed using EBSD technique and their Vicker's hardness were also measured. The results showed that MADF process effectively refined the microstructure of OFC with initial average grain size of $84.2{\mu}m$. The average grain sizes of specimens MADF processed for 1, 2, 3, 4 cycles were refined to be $8.5{\mu}m$, $2.2{\mu}m$, $1.5{\mu}m$, $1.1{\mu}m$, respectively. The grain refinement seemed to be saturated when OFC was MADF processed over 2 cycles. In the case of specimens subjected to two or more cycles of MADF, the degree of decrease in average grain size was drastically reduced as the number of cycles increased due to softening phenomena such as dynamic recovery or dynamic recrystallization during processing. The degree of increase in average Vicker's hardness was also dramatically reduced as the number of cycles increased due to the same reason.