• Electrical & Electronic Materials
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• v.1 no.3
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• pp.251-260
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• 1988

n형 GaAs에 음성접촉을 형성함에 있어서 Au-Ge 공융합금을 용해시키는 alloying 보다는 sintering을 필요로 하는 Su-Pd-Ge계의 새로운 융성접촉을 도입하였다. Au-Pd-Ge계의 최적의 음성조건을 조사하기 위하여 Au/Pd/Ge, Au/Ge/Pd, Au/Pd/Ge/Pd 그리고 Au/Pd/Au/Ge 음성접촉을 제조하였다. 비접촉저항을 조사하는데 있어서 sintering 온도는 390-450.deg.C사이였고 시간은 30초에서 6분 사이였다. Au-Pd-Ge계의 비접촉저항은 alloying된 Au/Pd/Ge 접촉의 그것에 필적할 만큼 낮았으며 특히 Au/Ge/Pd 접촉은 430.deg.C, 3분의 sintering 조건에서 가장 낮은 1.2*$10^{-6}$.OMEGA..$cm^{2}$의 비접촉저항을 나타냈다. Au/Ge/Pd 접촉의 표면형상 및 접촉패턴 가장자리는 450.deg.C에서 2분 이상 sintering된 접촉을 제외하고는 sintering 후에 as-deposited 상태와 다를 바가 없었다. 430.deg.C, 3분 sintering에서 가장 낮은 비접촉저항을 나타낸 Au/Ge/Pd 접촉의 비접촉저항은 430.deg.C에서 Ge/Pd 두께 변화에 비교적 변화가 적었다.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2765-2768
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• 2014

Flower-like Au nanoparticles, so-called Au nanoflowers (AuNFs), were synthesized by simply adding ascorbic acid to a gold acid solution in the presence of a chitosan biopolymer. The chitosan-entangled AuNFs exhibited strong plasmon absorption in the near-infrared (NIR) wavelength due to the aggregation of primary Au nanoparticles. The chitosan-entangled AuNFs were preferentially adsorbed by Raman-active 2-chlorothiophenol (CTP) molecules, and the CTP-encoded AuNFs (AuNF-CTPs) were subsequently coated with a thin silica layer by a sol-gel reaction with Si alkoxides. The silica-coated AuNFs (AuNF-CTPs@silica) exhibited the distinct Raman signals of adsorbed CTP molecules, as a potential nanoprobe with surface-enhanced Raman scattering (SERS).

• Electrical & Electronic Materials
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• v.9 no.10
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• pp.1013-1018
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• 1996

The annealing effects of Au/Te/Au/n-GaAs structure was investigated by using x-ray diffraction, scanning electron microscope, the specific contact resistance and I-V measurement. Increasing the annealing temperature, the intensity of Au-Ga peak by X-ray diffraction was increased. The Ga$\_$2/Te$\_$3/peak got evident for the samples annealed at 400.deg. C and GaAs peak by recrystallization appeared for the samples annealed at 500.deg. C. The variation from the schottky to low resistance contact was confirmed by I-V curve. The lowest value of the specific contact resistance of the samples annealed at 500.deg. C was 3.8*10$\^$-5/.ohm.-cm$\^$2/ but the value increased above 600.deg. C.

• Korean Journal of Materials Research
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• v.11 no.2
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• pp.76-81
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• 2001

In order to recover Au and Pd from the leaching solution of various electronic wastes by electrowinning, the electrochemical behavior of Au and Pd in hydorchloric acidic solution was investigated by means of voltammetry. The reduction potential of Au ion was 800mV and the limiting current appeared at 470mV in electrolytic solution of gold. The reduction potential of Pd ion was 500mv and the limiting current appeared at 150mV in electrolytic solution of Palladium. However, in Au-Pd electrolytic solution, the Potentials for reduction and the limiting current of Au decreased as the content of Pd in electrolyte increased, and the potentials for the limiting current of Au and Pd closed nearest together when percentage of Pd electrolytic solution was 37v71% in Au-Pd electrolyte.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.130-130
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• 2017

Au 합금 도금층은 내마모성 및 내식성이 우수하고 접촉저항이 낮기 때문에, 커넥터, 인쇄회로기판 등과 같은 전자부품의 접속단자부에 널리 적용되고 있다. 각 부품들을 효과적으로 전기적 신호를 통해 연결하기 위해서는 낮은 접촉저항이 요구되며, 이러한 Au 합금 도금층의 접촉저항은 합금 원소의 종류 및 함량, 용융 솔더와 전자부품을 고정시키는 표면실장공정에서 받는 theremal aging의 온도와 시간에 따라 변화된다. 현재 전자부품용 커넥터에 실시되고 있는 금 합금도금은 Au-0.3wt%Co합금, Au-0.2wt%Ni합금도금이 대부분 적용되고 있으며, 높은 순도(금 함유량 99.7wt%이상)로 인하여 금 사용량을 절감하기 어려운 실정이다. Sn은 Au와 높은 고용률을 갖는 합금을 형성하는 장점을 갖고 있기에 금 사용량 절감에 큰 기여를 할 수 있을 것으로 예상된다. 따라서 본 연구에서는 Sn을 합금 원소로 사용하여 높은 Sn함량을 갖는 Au 합금 도금층을 제작하고, 무연솔더의 융점보다 더 높은 온도인 533K에서 thermal aging을 실시하여, Sn함량별로 thermal aging에 따른 접촉저항과 솔더퍼짐성의 변화를 기존의 Co, Ni합금과 비교 조사하였다. 또한, 표면분석을 통하여 Au-Sn합금 도금층의 접촉저항이 변화하는 요인에 대해서도 고찰하였다. 표면적 $0.2dm^2$의 순수 동 시편 위에 약 $2{\mu}m$두께의 Ni도금을 실시한 후 Sn 함량을 다르게 준비한 도금 용액(Au 6g/L, Sn 1~8g/L)을 사용하여 Au-Sn합금 도금을 실시하였다. Au-Sn합금 도금층은 전류밀도 0.5ASD, 온도 $40^{\circ}C$에서 약 $0.1{\mu}m$두께가 되도록 도금하였으며, 두께는 형광X선 도금두께측정기로 측정하였다. 금 합금 도금층 내의 Sn함량은 Ti시편 위에 도금한 Au-Sn합금층을 왕수에 용해시킨 다음, ICP를 사용하여 분석하였다. Au-Sn합금 도금층의 접촉저항은 준비된 시편을 533K에서 1분 30초, 3분, 6분 간 열처리한 후, 5회 접촉저항을 측정하여 그 평균값으로 하중에 따른 금 합금 도금층의 접촉저항을 비교하였다. 솔더링성은 솔더볼을 합금 표면에 솔더페이스트를 이용하여 붙인 뒤 533K에서 30초간 열처리하고, 열처리 후 솔더볼의 높이 변화를 측정해 열처리 전 솔더볼의 높이에 비해 퍼진정도를 측정하였다. 또한, 도금층 내의 Sn함량에 따라서 접촉저항이 변화하는 요인을 분석하기 위해서 X선 광전자 분광기를 이용하여 도금층 표면의 정량 분석 및 화학적 결합상태를 분석하였다. ICP분석결과 Au-Sn합금층 내의 Sn함량은 도금용액의 조성별로 9~12wt% Sn 합금층이 형성된 것을 알 수 있었고 기존의 Au-Ni, Au-Co 합금층과 비교해 합금함량이 크게 증가된 것을 알 수 있었다. 또한 접촉저항 측정 결과, 기존의 Au-Ni, Au-Co합금층의 접촉저항과 비교했을 때 Au-Sn합금층의 접촉저항이 더 낮은 것을 알 수 있었다. 또한, 솔더퍼짐성 측정 결과 기존의 Au-Ni, Au-Co합금층과 비교해 솔더퍼짐성이 우수한 것을 확인할 수 있었다. 따라서 전자부품용 접점재료에 합금함량이 높은 Au-Sn합금층을 적용시키면 더 우수한 커넥터의 성능을 얻을 수 있을 뿐 아니라 경제적으로 큰 절약 효과를 기대할 수 있을 것으로 판단된다.

• Journal of Sensor Science and Technology
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• v.27 no.2
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• pp.76-81
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• 2018

Au@ZnO core-shell nanoparticles (NPs) were prepared by a simple method followed by heat-treatment for gas sensor applications. The advantage of the core-shell morphology was investigated by comparing the gas sensing performances of Au@ZnO core-shell NPs with pure ZnO NPs and different wt% of Au-loaded ZnO NPs. The crystal structures, shapes, sizes, and morphologies of all sensing materials were characterized by XRD, TEM, and HAADF-STEM. Au@ZnO core-shell NPs were nearly spherical in shape and Au NPs were encapsulated in the center with a 40-45 nm ZnO shell outside. The gas sensing operating temperature for Au@ZnO core-shell NPs was $300^{\circ}C$, whereas it was $350^{\circ}C$ for pure ZnO NPs and Au-loaded ZnO NPs. The maximum response of Au@ZnO core-shell NPs to 1000 ppm CO at $300^{\circ}C$ was 77.3, which was three-fold higher than that of 2 wt% Au-loaded ZnO NPs. Electronic and chemical effects were the primary reasons for the improved sensitivity of Au@ZnO core-shell NPs. It was confirmed that Au@ZnO core-shell NPs had better sensitivity and stability than Au-loaded ZnO NPs.

• Journal of Microbiology and Biotechnology
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• v.28 no.9
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• pp.1563-1572
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• 2018

Gold nanoparticles (AuNP) and their conjugates have been gaining a great deal of recognition in the medical field. Meanwhile, extended-spectrum ${\beta}$-lactamases (ESBL)-producing bacteria are also demonstrating a challenging problem for health care. The aim of this study was the biosynthesis of AuNP using Rosa damascenes petal extract and conjugation of ceftriaxone antibiotic (Cef-AuNP) in inhibiting ESBL-producing bacteria and study of in vitro anticancer activity. Characterization of the synthesized AuNP and Cef-AuNP was studied. ESBL-producing strains, Acinetobacter baumannii ACI1 and Pseudomonas aeruginosa PSE4 were used for testing the efficacy of Cef-AuNP. The cells of MCF-7 breast cancer were treated with previous AuNP and Cef-AuNP at different time intervals. Cytotoxicity effects of apoptosis and its molecular mechanism were evaluated. Ultraviolet-visible spectroscopy and Fourier transform infrared spectroscopy established the formation of AuNP and Cef-AuNP. Transmission electron microscope demonstrated that the formed nanoparticles were of different shapes with sizes of 15~35 nm and conjugation was established by a slight increase in size. Minimum inhibitory concentration (MIC) values of Cef-AuNP against tested strains were obtained as 3.6 and $4{\mu}g/ml$, respectively. Cef-AuNP demonstrated a decrease in the MIC of ceftriaxone down to more than 27 folds on the studied strains. The biosynthesized AuNP displayed apoptotic and time-dependent cytotoxic effects in the cells of MCF-7 at a concentration of $0.1{\mu}g/ml$ medium. The Cef-AuNP have low significant effects on MCF-7 cells. These results enhance the conjugating utility in old unresponsive ceftriaxone with AuNP to restore its efficiency against otherwise resistant bacterial pathogens. Additionally, AuNP may be used as an alternative chemotherapeutic treatment of MCF-7 cancer cells.

• Journal of Welding and Joining
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• v.29 no.6
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• pp.65-70
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• 2011

The effect of flip chip bonding parameters on formation of intermetallic compounds (IMCs) between Au stud bumps and Sn-3.5Ag solder was investigated. In this study, flip chip bonding temperature was performed at $260^{\circ}C$ and $300^{\circ}C$ with various bonding times of 5, 10, and 20 sec. AuSn, $AuSn_2$ and $AuSn_4$ IMCs were formed at the interface of joints and (Au, Cu)$_6Sn_5$ IMC was observed near Cu pad side in the joint. At bonding temperature of $260^{\circ}C$, $AuSn_4$ IMC was dominant in the joint compared to other Au-Sn IMCs as bonding time increased. At bonding temperature of $300^{\circ}C$, $AuSn_2$ IMC clusters, which were surrounded by $AuSn_4$ IMC, were observed in the solder joint due to fast diffusivity of Au to molten solder with increased bonding temperature. Bond strength of Au stud bump joined with Sn-3.5Ag solder was about 23 gf/bump and fracture mode of the joint was intergranular fracture between $AuSn_2$ and $AuSn_4$ IMCs regardless bonding conditions.

• Proceedings of the Materials Research Society of Korea Conference
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• 1999.11a
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• pp.79-79
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• 1999

• Electrical & Electronic Materials
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• v.6 no.6
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• pp.545-552
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• 1993

단층 금속 Al, Au 게이트 MESFET를 제작하여 열처리에 따른 쇼트키 계면에서의 상호확산 상태와 그에 따른 쇼트키 접촉특성 및 MESFET의 전기적 특성을 조사하였다. Al 및 Au 쇼트키 계면의 상호확산은 as-deposited 상태에서도 나타났으며 열처리 온도가 증가함에 따라 상호확산의 정도는 Au 접촉이 Al 접촉보다 컸다. 특히 Au 접촉에서 Ga의 외부확산이 현저했다 .Al 및 Au 게이트에 있어서 공통적으로 열처리 온도 증가에 따라 포화드레인 전류와 핀치오프 전압은 감소하였고 개방채널 저항은 증가하였으며 변화폭은 Au 게이트가 Al 게이트보다 컸다. Al 및 Au 접촉의 장벽높이는 as-deposited 상태에서 각각 0.70eV, 0.73eV로 페르미 준위는 1/2Eg 근처에 피닝되었다. Al 및 Au 접촉에 있어서 열처리 온도 증가에 따라 장벽높이는 각각 증가, 감소하였으며 이상계수는 각각 감소, 증가하였다. Al 접촉의 경우 열처리를 행함으로서 쇼트키 접촉특성이 개선됨을 확인할 수 있었다.