• Transactions of Materials Processing
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• v.17 no.5
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• pp.364-372
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• 2008

In this study, the circumferential creep behaviors ofpilgered advanced Zirconium alloy tubes such as Zr-Nb-O and Zr-Nb-Sn-Fe were investigated in the temperature range of $400\sim500^{\circ}C$ and in the stress range of 80$\sim$150MPa. The test results indicate that the stress exponent for the steady-state creep rate of the Zr-Nb-Sn-Fe alloy decreases with the increase of stress(from 6$\sim$7 to 4), while that of the Zr-Nb-O alloy is nearly independent of stress(5$\sim$6). The activation energy of creep deformation is found to be nearly the same as the activation energy for Zr self diffusion. This indicates that the creep deformation may be controlled by dislocation climb mechanism in Zr-Nb-O. On the other hand, the transition of stress exponent(from 6-7 to 4) in Zr-Nb Sn-Fe strongly suggests the transition of the rate controlling mechanism at high stresses. The lower stress exponent at high stresses in Zr-Nb-Sn-Fe can be explained by the dynamic deformation aging effect caused by interaction of dislocations with Sn substitutional atoms.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.199-202
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• 1999

반강유전 물질인 Pb[(Zr. Sn)Ti]NbO₃를 La/sub 0.5/Sr/sub 0.5/CoO₃/Pt/Ti/SiO₂/Si 기판상에 RF 마그네트론 스퍼터링 방법으로 박막화하여 그 결정성과 전기적 특성을 조사하였다. 80 W의 RF power, 400℃의 기판온도, Ar:O₂= 9:0.5의 분위기에서 증착되고, 650 ℃에서 10초동안 RTP(Rapid Thermal Process) 방법으로 열처리된 박막이 가장 우수한 페로브스카이트 구조를 보였으며, 10 ㎑ 에서 유전상수(ε')는 721, 유전손실(tan δ)은 0.06을 나타내었다. 잔류분극(Pr)은 15.5 μC/㎠ 였으며, 항전계(Ec)는 51 ㎸/㎝로 비교적 낮은 값을 나타내었다.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1779-1781
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• 2000

Pd doped $SnO_2$ thin film sensors were prepared on alumina substrate by rf magnetron sputtering method. The sensitivity of thin film was investigated by varying the heat-treatment temperature, film thickness and gas species. The thin film heat-treated at 600$^{\circ}C$ and film thickness of 5000${\AA}$ showed the highest sensitivity at an operating temperature of 400$^{\circ}C$.

• Journal of Sensor Science and Technology
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• v.4 no.2
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• pp.51-57
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• 1995

Indium Tin Oxide (ITO) thin films have been fabricated by the rf magnetron sputtering technique with a target of a mixture $In_{2}O_{3}$ (90mol%) and $SnO_{2}$ (10mol%). We prepared ITO thin films with substrate temperature 100, 200, 300, 400, $500^{\circ}C$ and post-annealing temperature 300, 400, $500^{\circ}C$. And we analyzed X -ray diffraction patterns, electrical properties, transmission spectra and SEM photographs. As a result, the crystallinity, electrical conductivity and transmittance of ITO thin films were improved with increasing substrate temperature. But, as increasing post-annealing temperature in air, conductivity of the film was decreased. When the ITO thin film was fabricated with substrate temperature of $500^{\circ}C$ and thickness of $3000{\AA}$, its resistivity and transmittance were about $2{\times}10^{-4}{\Omega}cm$ and 85% or more, respectively.

• Journal of the Mineralogical Society of Korea
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• v.4 no.1
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• pp.43-50
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• 1991

Two solid solution-type phases has been experimentally found in the quaternary system Cu-Fe-Sn-S:$(Fe, Cu, Sn)_{1+x}$ and $Cu_{2-x}Fe_(1+x}SnS_4$. These solid solutions are stable around the CuS-FeS-SnS referecne plane in the composition tetrahedron. One is the sphalerite-type monosulfide solid solution which has a extensive stability range with varying degrees of sulfur/metal ratio 9.7-1.0/1.0. The other is tetrahedrite-type phase $Cu_{2-y)Fe_{1+y}SnS_4(y_{max}=0.4)$ which is stable along the $Cu_2FeSnS_4-FeS$ tie line, but shows no phase transformation in the subsolidus range and decomposes incongruently at the range of 835-862${\circ}C$, depending on the compositional variation. Particularly, the latter phase shows the characteristic superstructure reflections, indicating that it is a derivative of sphalerite structure. The stability field of these two sphalerite-type phases are defined on the basis of diffraction pattern and optical homogeneity of the synthetic materials at the temperature range of 700-400${\circ}C$.

• Journal of the Korean Institute of Telematics and Electronics
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• v.17 no.6
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• pp.65-71
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• 1980

The Sn O2-Si Heterojunction sola cells are Prepared by vacuum deposition of SnO2 on N- and P-type Si - wafers arts the effects of annealing on the Solar cell characteiistics are presented. The existence of optimumannealins temperature for maximum open-circuit voltage and short - circuit current of the solar cell is observed. The optimum tomperature, when low resistivity (7- 2.3 [$\Omega$.cm]) P-and N-type Si -wafers are used, is 500 [$^{\circ}C$] End 400 [$^{\circ}C$] when high resistivity[41-58 [$\Omega$.cm]) P-type Si-wafers are used.

• Korean Journal of Materials Research
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• v.14 no.12
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• pp.840-845
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• 2004

Tin dioxide ($SnO_2$) thin films were prepared on Si(100) substrate by PE-ALD using the $DBDTA((CH_{3}CO_2)_{2}Sn[(CH_2)_{3}CH_3]_2)$ Precursor. The properties were studied as a function of source temperature, substrate temperature, and purging time. Scanning probe microscopic images at the source temperature $50^{\circ}C$ and the substrate temperature $300^{\circ}C$ shows lower roughness than those $40/60^{\circ}C$ source and $200/400^{\circ}C$ substrate temperature samples. The purging time for optimum process was 8sec and the deposition rate was about 1 nm per 10 cycles. The conductance of $SnO_2$ thin film showed a constant region in the range of $200^{\circ}C\;to\;500^{\circ}C$. The thin films deposited for 200 cycle show a better sensitivity to CO gas.

• Korean Journal of Materials Research
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• v.9 no.11
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• pp.1083-1087
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• 1999

Microstructures and the gas-sensing characteristics of the $\textrm{SnO}_2$ thin films were studied, which were deposited at various conditions (rf power, sample temperature, $\textrm{O}_2$/Ar ratio) by the rf magnetron sputtering. As a result, six typical microstructures were derived, such as amorphous(A), amorphous mixed with polycrystalline grains (A+P), polycrystalline with random crystalographic orientation (P), fine columnar (FC), coarse columnar (CC) and Zone T (T) with dense fiberous structure. Typically, A, A+ P, and P structures were formed when no $\textrm{O}_2$ was added to the sputter gas, whereas FC, CC, and T structures were obtained when $\textrm{O}_2$ was added. The A structure formed at low rf power and low temperature, the A+P at high rf power and low temperature, and the P at high rf power and high temperature. The FC structure was obtained at low rf power and low temperature. the CC at low rf power and high temperature, and the T at high rf power and low temperature. Results of the gas-sensing test of the sensor chips fabricated from the typical films indicated that the fine columnar microstructure shows the highest sensitivity both at $300^{\circ}C$ and $400^{\circ}C$. It was proposed that this is due to the high specific surface area of the micro-columns.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.338-338
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• 2013

Monolithic three-dimensional integrated circuits (3D-ICs) 구현 시 bonding 과정에서 발생되는 aluminum (Al) 이나 copper (Cu) 등의 interconnect metal의 확산, 열적 스트레스, 결함의 발생, 도펀트 재분포와 같은 문제들을 피하기 위해서는 저온 공정이 필수적이다. 지금까지는 polymer 기반의 bonding이나 Cu/Cu와 같은 metal 기반의 bonding 등과 같은 저온 bonding 방법이 연구되어 왔다. 그러나 이와 같은 bonding 공정들은 공정 시 void와 같은 문제가 발생하거나 공정을 위한 특수한 장비가 필수적이다. 반면, 두 물질의 합금을 이용해 녹는점을 낮추는 eutectic bonding 공정은 저온에서 공정이 가능할 뿐만 아니라 void의 발생 없이 강한 bonding 강도를 얻을 수 있다. Aluminum-germanium (Al-Ge) 및 aluminum-indium (Al-In) 등의 조합이 eutectic bonding에 이용되어 각각 $424^{\circ}C$ 및 $454^{\circ}C$의 저온 공정을 성취하였으나 여전히 $400^{\circ}C$이상의 eutectic 온도로 인해 3D-ICs의 구현 시에는 적용이 불가능하다. 이러한 metal 조합들에 비해 indium (In)과 tin (Sn)은 각각 $156^{\circ}C$ 및 $232^{\circ}C$로 굉장히 낮은 녹는점을 가지고 있기 때문에 In-Sn 조합은 약 $120^{\circ}C$ 정도의 상당히 낮은eutectic 온도를 갖는다. 따라서 본 연구팀은 In-Sn 조합을 이용하여 $200^{\circ}C$ 이하에서monolithic 3D-IC 구현 시 사용될 eutectic bonding 공정을 개발하였다. 100 nm SiO2가 증착된 Si wafer 위에 50 nm Ti 및 410 nm In을 증착하고, 다른Si wafer 위에 50 nm Ti 및 500 nm Sn을 증착하였다. Ti는 adhesion 향상 및 diffusion barrier 역할을 위해 증착되었다. In과 Sn의 두께는 binary phase diagram을 통해 In-Sn의 eutectic 온도인 $120^{\circ}C$ 지점의 조성 비율인 48 at% Sn과 52 at% In에 해당되는 410 nm (In) 그리고 500 nm (Sn)로 결정되었다. Bonding은 Tbon-100 장비를 이용하여 $140^{\circ}C$, $170^{\circ}C$ 그리고 $200^{\circ}C$에서 2,000 N의 압력으로 진행되었으며 각각의 샘플들은 scanning electron microscope (SEM)을 통해 확인된 후, 접합 강도 테스트를 진행하였다. 추가로 bonding 층의 In 및 Sn 분포를 확인하기 위하여 Si wafer 위에 Ti/In/Sn/Ti를 차례로 증착시킨 뒤 bonding 조건과 같은 온도에서 열처리하고secondary ion mass spectrometry (SIMS) profile 분석을 시행하였다. 결론적으로 본 연구를 통하여 충분히 높은 접합 강도를 갖는 In-Sn eutectic bonding 공정을 $140^{\circ}C$의 낮은 공정온도에서 성공적으로 개발하였다.

• Journal of Sensor Science and Technology
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• v.6 no.4
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• pp.274-279
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• 1997

NOx sensors using tungsten oxide films as a base material were prepared and their electrical and sensing characteristics have been investigated. The $WO_{3}$ thick films doped with $SnO_{2}$ or $TiO_{2}$ showed higher sensitivity and better sorption characteristics to NOx gas than the pure $WO_{3}$ films material in air at operating temperature of $400^{\circ}C$. By addition of noble catalysts, such as Ru or Au, to the $TiO_{2}-WO_{3}$ thick films, their sensitivity, recovery and selectivity to NOx gas were found to be more enhanced.