• 한국전기전자재료학회논문지
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• 제16권7호
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• pp.564-568
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• 2003

The etching of Au thin films have been performed in an inductively coupled CF$_4$/Cl$_2$/Ar plasma. The etch rates were measured as CF$_4$ contents added from 0 to 30 % to Cl$_2$/Ar plasma, of which gas mixing ratio was fixed at 20%. Other parameters were fixed at an rf power of 700 W, a dc bias voltage of 150 V, a chamber pressure of 15 mTorr, and a substrate temperature of 3$0^{\circ}C$. The highest etch rate of the Au thin film was 3700 $\AA$m/min at a 10% additive CF$_4$ into Cl$_2$/Ar plasma. The surface reaction of the etched Au thin films was investigated using x-ray photoelectron spectroscopy (XPS) analysis. XPS analysis indicated that Au reacted with Cl and formed Au-Cl, which is hard to remove on the surface because of its high melting point. The etching products could be sputtered by Ar ion bombardment.

• Transactions on Electrical and Electronic Materials
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• 제4권3호
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• pp.1-4
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• 2003

The etching of Au thin films has been performed in an inductively coupled $CF_4 / Cl_2 / Ar$ plasma. The etch properties including etch rate and selectivity were examined as $CF_4$ content adds from o to $30\%$ to $Cl_2/Ar$ plasma. The $Cl_2/(Cl_2 + Ar)$ gas mixing ratio was fixed at $20\%$. Other parameters were fixed at an rf power of 700 W, a dc bias voltage of -150 V, a chamber pressure of 15 mTorr, and a substrate temperature of $30^{\circ}C$. The highest etch rate of the Au thin film was 370 nm/min at a $10\%$ additive $CF_4$ into $Cl_2/Ar$ gas mixture. The surface reaction of the etched Au thin films was investigated using x-ray photoelectron spectroscopy (XPS) analysis. The XPS analysis shows that the intensities of Ail peaks are changed, indicating that there is a chemical reaction between Cl and Au. Au-Cl is hard to remove on the surface because of its high melting point. However, etching products can be sputtered by Ar ion bombardment.

• 산업기술연구
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• 제29권B호
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• pp.229-232
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• 2009

We prepared gold nanoparticles (Au NPs) by reduction-oxidation reaction between $HAuCl_4$ and trisodium citrate and measured the size and morphology of Au NPs by TEM for various molar ratios of $HAuCl_4$ to citrate and for various concentrations of $HAuCl_4$. UV-vis spectroscopy was used to characterize the optical properties of Au NPs. Au NPs in the size range from 14.3 nm to 20.3 nm were prepared with monodisperse distribution.

• Bulletin of the Korean Chemical Society
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• 제29권8호
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• pp.1441-1442
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• 2008

• 한국진공학회지
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• 제22권5호
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• pp.270-275
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• 2013

화학 기상 증착법에 의해 제작한 단층 그래핀을 300 nm $SiO_2$/Si와 석영기판 위에 전사한 후 도핑하기 위해 그래핀 표면에 $AuCl_3$ 용액의 농도를 1에서 10 mM까지 변화시키면서 스핀코팅 하였다. 도핑농도에 따른 그래핀의 특성을 여러 구조적, 광학적, 및 전기적 실험기법으로 분석한 결과, 도핑 농도가 증가함에 따라 그래핀의 p형 특성이 더욱 강해진다는 것을 라만 주파수/최고점 세기 비율, 면저항, 일함수, 및 디락점 등의 변화로 확인할 수 있었다. 특히, 그래핀 전계효과 트랜지스터의 드레인 전류-게이트 전압 곡선 측정을 통해 처음으로 도핑농도의 증가에 따라 전하 이동도를 자세히 측정한 결과, 도핑농도가 증가할 때 전자의 이동도는 크게 감소한 것에 비해 정공의 이동도는 매우 적게 변화하였다. 이 결과는 $AuCl_3$가 그래핀의 p형 도핑 불순물로서 매우 우수하다는 것을 의미하여 향후 도핑된 그래핀의 소자활용에 있어 매우 유용할 것으로 전망된다.

• 한국재료학회지
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• 제16권8호
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• pp.524-528
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• 2006

On the synthesis of Au/$TiO_2$ core-shell structure nanoparticle, the effect of concentration of $Ti^{4+}$ and reaction temperature on the morphology and optical property of Au/$TiO_2$ core-shell nanoparticles is examined. A gold colloid was prepared by $HAuCl_4{\cdot}4H_2O\;and\;C_6H_5Na_3{\cdot}2H_2O$. Titanium stock solution was prepared by mixing solution of titanium(IV) isopropoxide (TTIP) and triethanolamine (TEOA). The concentrations of $Ti^{4+}$ stock solution were adjusted to $10.01{\sim}0.3$ mM, and then the gold colloid is added to the $Ti^{4+}$ stock solution. Au/$TiO_2$ core-shell structure nanoparticles could be prepared by the hydrolysis of the $Ti^{4+}$ stock solution at $80^{\circ}C$. The size of synthesized Au nanoparticles was 15 nm. The thickness of $TiO_2$ shell on the surface of gold particles was about 10 nm. The absorption peak of synthesized Au/$TiO_2$ core-shell nanoparticles shifted towards the red end of the spectrum by about 3 nm because of the formation of $TiO_2$ shell on the surface of gold particles. The good $TiO_2$ shell is produced when $Ti^{4+}$ concentration is varied between 0.01 and 0.05 mM, and reaction temperature is maintained at $80^{\circ}C$. The crystal structure of $TiO_2$ shell was amorphous.

• Bulletin of the Korean Chemical Society
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• 제35권7호
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• pp.2072-2076
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• 2014

Sub-micrometer size gold particles were electrodeposited on a transparent fluorine-doped tin oxide (FTO) from acetonitrile solution containing $AuCl_4{^-}$ and tetramethylammonium tetraflouroborate (TMATFB) for detecting $NO_2{^-}$. A series of two-electron ($2e^-$) and one-electron ($1e^-$) reductions of the $AuCl_4{^-}-AuCl_2{^-}-Au$ redox systems were observed at FTO and a highly stable and homogeneous distribution of Au on FTO (Au/FTO) was obtained by stepping the potential from 0 to -0.55 V (vs. Ag/$Ag^+$). The Au/FTO electrode exhibited sufficiently high catalytic activity toward the oxidation of $NO_2{^-}$ with a detection limit (S/N = 3) and sensitivity of 2.95 ${\mu}M$ and 223.4 ${\mu}A{\cdot}cm^{-2}{\cdot}mM^{-1}$, respectively, under optimal conditions. It exhibited an interference-free signal for $NO_2{^-}$ detection with excellent recoveries from real samples.

• 한국세라믹학회지
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• 제43권2호
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• pp.114-120
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• 2006

Nano-size Au particle doped $TiO_2$ films were prepared with $Ti(OC_3H_7^i)_4$, polyvinylpyrrolidone(PVP), $HAuCl_4$ and $C_3H_7OH$ etc. by sol-gel method. $TiO_2$ gel films were obtained by the dip-coating method on the $SiO_2$ glass substrates, and then heat-treated at $700^{\circ}C$ for 10 min. The thickness of $TiO_2$ films were $0.7\~1.8\;{\mu}m$. It was found that the thickness of films prepared from PVP containing solution was about $2\~8$ times higher values than that of thin films without PVP. The size of Au particles doped in the films were about $350\~750\;nm$. Nano-size Au particle dispersed $TiO_2$ films showed high absorption peak at visible region 450nm, which made them good candidates for non-linear optical materials and photo-catalytic materials. The contact angle of $TiO_2$ film for water was $12.5^{\circ}$, and therefore it is clear that $TiO_2$ films have very high hydrophilic properties and the self-cleaning effects.

• 분석과학
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• 제37권1호
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• pp.47-62
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• 2024

Abu Gurdi area is located in the South-eastern Desert of Egypt which considered as volcanic massive sulfide deposits (VMS). The present work aims at investigating the ore mineralogy of Abu Gurdi region in addition to the effectiveness of the hydrometallurgical route for processing these ores using alkaline leaching for the extraction of Zn, Cu, and Pb in the presence of hydrogen peroxide, has been investigated. The factors affecting the efficiency of the alkaline leaching of the used ore including the reagent composition, reagent concentration, leaching temperature, leaching time, and Solid /Liquid ratio, have been investigated. It was noted that the sulfide mineralization consists mainly of chalcopyrite, sphalerite, pyrite, galena and bornite. Gold is detected as rare, disseminated crystals within the gangue minerals. Under supergene conditions, secondary copper minerals (covellite, malachite, chrysocolla and atacamite) were formed. The maximum dissolution efficiencies of Cu, Zn, and Pb at the optimum leaching conditions i.e., 250 g/L NaCO₃ - NaHCO₃ alkali concentration, for 3 hr., at 250 ℃, and 1/5 Solid/liquid (S/L) ratio, were 99.48 %, 96.70 % and 99.11 %, respectively. An apparent activation energy for Zn, Cu and Pb dissolution were 21.599, 21.779 and 23.761 kJ.mol^-1, respectively, which were between those of a typical diffusion-controlled process and a chemical reaction-controlled process. Hence, the diffusion of the solid product layer contributed more than the chemical reaction to control the rate of the leaching process. High pure Cu(OH)₂, Pb(OH)₂, and ZnCl₂ were obtained from the finally obtained leach liquor at the optimum leaching conditions by precipitation at different pH. Finally, highly pure Au metal was separated from the mineralized massive sulfide via using adsorption method.

• 한국결정성장학회지
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• 제29권4호
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• pp.179-186
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• 2019

본 연구에서는 $Ga_2O_3$ 박막의 구조적 특성과 Ti/Au 전극을 증착하여 제작된 metal-semiconductor-metal (MSM) photodetector 소자의 광학적, 전기적 특성에 대해 연구하였다. 유기 금속 화학 증착법(metal organic chemical vapor deposition, MOCVD)을 이용해 서로 다른 온도에서 $Ga_2O_3$ 박막을 성장하였다. 성장온도에 따라 $Ga_2O_3$의 결정상이 ${\varepsilon}$-상에서 ${\beta}$-상으로 변화하는 것을 확인할 수 있었다. X-선 회절 분석(X-ray diffraction, XRD) 결과로 ${\varepsilon}-Ga_2O_3$의 결정구조를 확인하였고, 주사 전자 현미경(scanning electron microscopy, SEM) 이미지로 결정구조의 형성 메커니즘에 대해 논의하였다. 음극선 발광(Cathode luminescence, CL) 측정으로 $Ga_2O_3$의 발광성 천이에 관여하는 에너지 준위의 형성 원인에 대해 논의하였다. 제작된 MSM photodetector 소자의 외부 광에 대한 전류-전압 특성과 시간 의존성 on/off 광 응답 특성을 통해 ${\varepsilon}-Ga_2O_3$로 제작한 photodetector는 가시광보다 266 nm UV 파장 영역에서 훨씬 뛰어난 광전류 특성을 보이는 것을 확인하였다.