• Resources Recycling
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• v.10 no.5
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• pp.29-35
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• 2001

This study was carried out to recover gold, silver and valuable metals from the printed circuit boards (PCBs) of waste computers. PCBs samples were crushed under 1 mm by a shredder and separated into 30% conducting and loft nonconducting materials by an electrostatic separator. The conducting materials contained valuable metals which were then used as feed materials for magnetic separation. 42% of magnetic materials from the conducting materials was removed by magnetic separation as nonvaluable materials and the others, 58% of non magnetic materials, was used as leaching samples containing 0.227 mg/g Au and 0.697 mg/g Ag. Using the materials of leaching from magnetic separation, more than 95% of copper, iron, zinc, nickel and aluminium was dissolved in 2.0M sulfuric acid solution, added with 0.2M hydrogen peroxide at $85^{\circ}C$. Au and Ag were not extracted in this solution. On the other hand, more than 95% of gold and 100% of silver were leached by the selective leaching with a mixed solvent (0.2M($NH_4$)$_2$$S_2$$O_3$,0.02M $CuSO_4$,0.4M $NH_4$OH). Finally, the residues were reacted with a NaCl solution to leach Pb whereas sulfuric acid was used to leach Sn. Recoveries reached 95% and 98% in solution, respectively.

• Bulletin of the Korean Chemical Society
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• v.32 no.3
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• pp.847-851
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• 2011

This study examined In-Zn-Sn-O (IZTO) films deposited on glass substrates by pulsed DC magnetron sputtering with various substrate temperatures. The structural, electrical, optical properties were analyzed. Xray diffraction showed that the IZTO films prepared at temperatures > $150^{\circ}C$ were crystalline which adversely affected the electrical properties. Amorphous IZTO films prepared at $100^{\circ}C$ showed the best properties, such as a low resistivity, high transmittance, figure of merit, and high work function of $4.07{\times}10^{-4}\;{\Omega}$, 85%, $10.57{\times}10^{-3}\;{\Omega}^{-1}$, and 5.37 eV, respectively. This suggests that amorphous IZTO films deposited at relatively low substrate temperatures ($100^{\circ}C$) are suitable for electrode applications, such as OLEDs as a substitute for conventional crystallized ITO films.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.313-313
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• 2009

OLED 소자는 직접발광, 광시야각, 그리고 빠른 응답속도 때문에 동영상에 적합하여 최근 각광받고 있는 디스플레이장치 중의 하나이다. OLED 소자의 양극재료로는 높은 광투과율과 $\sim10^{-4}{\Omega}\;cm$ 수준의 낮은 전기 비저항을 갖는 ITO (Sn-doped $In_2O_3$)가 널리 사용되고 있다. 하지만 원료 물질인 인듐의 수급량 부족으로 인한 문제점과 독성, 저온증착의 어려움, 스퍼터링시 음이온 충격에 의한 막 손상으로 저항의 증가의 문제점이 있고, 또한 액정디스플레이의 투명전극으로 사용될 경우 $400\;^{\circ}C$정도의 높은 온도와 수소 플라즈마 분위기에서 장시간 노출 시 열화로 인한 광학적 특성변화가 문제가 된다. 반면에 Al이 도핑 된 ZnO (AZO)박막은 넓은 밴드갭 (3.37eV)와 400nm에서 700nm 사이의 가시광 영역에서 80% 이상의 우수한 투과성을 지니고 있다. 특히 Al이 도핑된 ZnO는 박막의 전기적 특성이 크게 향상되어 디스플레이나 태양전지로의 응용이 가능하다. 또한 비교적 낮은 비용과 플라즈마에서의 안정성, 무독성, 그리고 전기전도성과 같은 많은 이점이 있다. 그 결과 AZO 박막은 ITO기판을 대안하는 지원물질로 활발히 연구가 진행되고 있다. 본 연구에서는 TCO 박막의 면 저항과 표면 거칠기에 따른 OLED 소자의 특성을 분석하였다. ITO와 AZO 박막은 챔버 내 다양한 가스 분위기(Ar, Ar+$O_2$ and Ar+$H_2$)에서 R.F Magnetron Sputtering방법으로 증착하였다. TCO 박막의 구조적인 이해를 돕기 위해서 X-ray diffraction 과 FESEM으로 분석하였다. 광학적 투과도와 박막의 두께는 ultraviolet spectrophotometer (Varian, cary-500)와 surface profile measurement system으로 각각 측정하였다. 면저항 charge carrier 농도, 그리고 TCO 박막의 이동도와 같은 전기적특성은 four-point probe와 hall effect measurement(HMS-3000)로 각각 측정하였다. TCO 박막의 표면 거칠기 조절을 위해 photo lithography 공정을 사용하여 TCO 박막을 화학에칭 하였다. 미세사이즈 패턴 마스크가 사용되었으며 에칭의 깊이는 에칭시간에 따라 조절하였다. TCO 박막의 표면 형태는 FESEM과 AFM으로 관찰하였다. 투명전극으로 사용되는 ITO 및 AZO 기판 상용화를 위해 ITO 및 AZO 기판 위에 ${\alpha}$-NPB, Alq3, LiF, Al 의 순서로 증착 및 패터닝함으로써 OLED 소자를 제작하였다. 전류밀도와 전압 그리고 발광휘도와 전압과 같은 전기적 특성은 spectrometer(minolta CS-1000A)를 이용하여 측정하였다.

• Journal of the Korean Applied Science and Technology
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• v.33 no.4
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• pp.734-740
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• 2016

The micron-sized indium zinc tin oxide (IZTO) particles were prepared by spray pyrolysis from aqueous precursor solution for indium, zinc, and tin and organic additives such as citric acid (CA) and ethylene glycol (EG) were added to aqueous precursor solution for indium, zinc, and tin. The obtained IZTO particles prepared by spray pyrolysis from the aqueous solution without organic additives had spherical and filled morphologies, whereas the IZTO particles obtained with organic additives had more hollow and porous morphologies. The micron-sized IZTO particles with organic additives were changed fully to nano-sized IZTO particles, whereas the micron-sized IZTO particles without organic additives were not changed fully to nano-sized IZTO particle after post-treatment at $700^{\circ}C$ for 2 hours and wet-ball milling for 24 hours. Surface resistances of micron-sized IZTO's before post-heat treatment and wet-ball milling were much higher than those of nano-sized IZTO's after post-heat treatment and wet-ball milling. From IZTO with composition of 80 wt. % $In_2O_3$, 10 wt. % ZnO, and 10 wt. % $SnO_2$ which showed a smallest surface resistance IZTO after post-heat treatment and wet-ball milling, thin films were deposited on glass substrates by pulsed DC magnetron sputtering, and the electrical and optical properties were investigated.

• Korean Journal of Materials Research
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• v.20 no.12
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• pp.676-680
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• 2010

Most TCOs such as ITO, AZO(Al-doped ZnO), FTO(F-doped $SnO_2$) etc., which have been widely used in LCD, touch panel, solar cell, and organic LEDs etc. as transparent electrode material reveal n-type conductivity. But in order to realize transparent circuit, transparent p-n junction, and introduction of transparent p-type materials are prerequisite. Additional prerequisite condition is optical transparency in visible spectral region. Oxide based materials usually have a wide optical bandgap more than ~3.0 eV. In this study, single-phase transparent semiconductor of $SrCu_2O_2$, which shows p-type conductivity, have been synthesized by 2-step solid state reaction at $950^{\circ}C$ under $N_2$ atmosphere, and single-phase $SrCu_2O_2$ thin films of p-type TCOs have been deposited by RF magnetron sputtering on alkali-free glass substrate from single-phase target at $500^{\circ}C$, 1% $H_2$/(Ar + $H_2$) atmosphere. 3% $H_2$/(Ar + $H_2$) resulted in formation of second phases. Hall measurements confirmed the p-type nature of the fabricated $SrCu_2O_2$ thin films. The electrical conductivity, mobility of carrier and carrier density $5.27{\times}10^{-2}S/cm$, $2.2cm^2$/Vs, $1.53{\times}10^{17}/cm^3$ a room temperature, respectively. Transmittance and optical band-gap of the $SrCu_2O_2$ thin films revealed 62% at 550 nm and 3.28 eV. The electrical and optical properties of the obtained $SrCu_2O_2$ thin films deposited by RF magnetron sputtering were compared with those deposited by PLD and e-beam.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.52-52
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• 2018

Only approximately 30% of fossil fuel energy is used; therefore, it is desirable to utilize the huge amounts of waste energy. Thermoelectric (TE) materials that convert heat into electrical power are a promising energy technology. The TE materials can be formed either as thin films or as bulk semiconductors. Generally, thin-film TE materials have low energy conversion rates due to their thinness compared to that in bulk. However, an advantage of a thin-film TE material is that the efficiency can be smartly engineered by controlling the nanostructure and composition. Especially nanostructured TE thin films are useful for mitigating heating problems in highly integrated microelectronic devices by accurately controlling the temperature. Hence, there is a rising interest in thin-film TE devices. These devices have been extensively investigated. It is demonstrated that transparent amorphous oxide semiconductors (TAOS) can be excellent thermoelectric (TE) materials, since their thermal conductivity (${\kappa}$) through a randomly disordered structure is quite low, while their electrical conductivity and carrier mobility (${\mu}$) are high, compared to crystalline semiconductors through the first-principles calculations and the various measurements for the amorphous In-Zn-O (a-IZO) thin film. The calculated phonon dispersion in a-IZO shows non-linear phonon instability, which can prevent the transport of phonon. The a-IZO was measured to have poor ${\kappa}$ and high electrical conductivity compared to crystalline $In_2O_3:Sn$ (c-ITO). These properties show that the TAOS can be an excellent thin-film transparent TE material. It is suggested that the TAOS can be employed to mitigate the heating problem in the transparent display devices.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.175-175
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• 2010

Transparent conducting oxide (TCO) films are widely used as transparent conducting thin film material for application in various fields such as solar cells, optoelectronic devices, heat mirrors and gas sensors, etc. Recently the increased utilization of many transparent electrodes has accelerated the development of inexpensive TCO materials. Indium tin oxide (ITO) film is well-known for TCO materials because of its low resistivity, but there is disadvantage that it is too expensive. ZnO film is cheaper than ITO but it shows thermally poor stability. On the contrary, antimony-doped tin oxide films (ATO) are more stable than TCO films such as Al-doped zinc oxide (AZO) and ITO. Moreover, SnO2 film shows the best thermal and chemical stability, low cost and mechanical durability except the poor conductivity. However, annealing is proved to improve the conductivity of ATO film. Therefore, in this work, antimony (6 wt%) doped tin oxide films to improve the conductivity were deposited on 7059 corning glass by RF magnetron sputtering method for the application to transparent electrodes. In general, of all TCO films, glass is the most commonly selected substrate. However, for future development in flexible devices, glass is limited by its intrinsic inflexibility. In this study, we report the growth and properties of antimony doped tin oxide (ATO) films deposited on PES flexible substrate by using RF magnetron sputtering. The optimization process was performed varying the sputtering parameters, such as RF power and working pressure, and parameter effect on the structural, electrical and optical properties of the ATO films were investigated.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.324-326
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• 2016

In this study, we have investigated indium tin zinc oxide (ITZO) as an active channel for non-volatile memory (NVM) devices. The electrical and memory characteristics of NVM devices using multi-stack gate insulator SiO2/SiOx/SiOxNy (OOxOy) with Si-rich SiOx for charge storage layer were also reported. The transmittance of ITZO films reached over 85%. Besides, ITZO-based NVM devices showed good electrical properties such as high field effect mobility of 25.8 cm2/V.s, low threshold voltage of 0.75 V, low subthreshold slope of 0.23 V/dec and high on-off current ratio of $1.25{\times}107$. The transmission Fourier Transform Infrared spectroscopy of SiOx charge storage layer with the richest silicon content showed an assignment at peaks around 2000-2300 cm-1. It indicates that many silicon phases and defect sources exist in the matrix of the SiOx films. In addition, the characteristics of NVM device showed a retention exceeding 97% of threshold voltage shift after 104 s and greater than 94% after 10 years with low operating voltage of +11 V at only 1 ms programming duration time. Therefore, the NVM fabricated by high transparent ITZO active layer and OOxOy memory stack has been applied for the flexible memory system.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.2
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• pp.198-203
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• 2016

We investigate the effects of magnesium (Mg) suppressor layer on the electrical performances and stabilities of amorphous indium-zinc-tin-oxide (a-ITZO) thin-film transistors (TFTs). Compared to the ITZO TFT without a Mg suppressor layer, the ITZO:Mg TFT exhibits slightly smaller field-effect mobility and much reduced subthreshold slope. The ITZO:Mg TFT shows improved electrical stabilities compared to the ITZO TFT under both positive-bias and negative-bias-illumination stresses. From the X-ray photoelectron spectroscopy O1s spectra with fitted curves for ITZO and ITZO:Mg films, we observe that Mg doping contributes to an enhancement of the oxygen bond without oxygen vacancy and a reduction of the oxygen bonds with oxygen vacancies. This result shows that the Mg can be an effective suppressor in a-ITZO TFTs.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.245-245
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• 2012

차세대 디스플레이로 각광받고 있는 AMOLED에 대한 관심이 높아짐에 따라 구동 소자의 연구가 활발히 이루어지고 있다. 산화물 반도체 박막 트랜지스터는 비정질 실리콘 박막 트랜지스터에 비해 100 $cm^2$/Vs 이하의 높은 이동도와 우수한 전기적 특성으로 AMOLED 구동 소자로서 학계에서 입증되어왔고, 현재 여러 기업에서 산화물 반도체를 이용한 박막 트랜지스터 제작 연구가 활발히 이루어지고 있다. 본 연구는 열처리 조건을 가변하여 제작한 산화물 반도체 박막 트랜지스터의 전기적 특성 분석을 목적으로 한다. 실리콘 기판에 oxidation 공정을 이용하여 SiO2 100 nm, DC스퍼터링을 이용하여 ITZO (Indium-Tin-Zinc Oxide) 산화물 반도체 박막 50 nm, 증착된 산화물 반도체 박막의 열처리 후, evaporation을 이용하여 source/drain 전극 Ag 150 nm 증착하여 박막 트랜지스터를 제작하였다. 12 sccm의 산소유량, 1시간의 열처리 시간에서 열처리 온도 $400^{\circ}C$, $200^{\circ}C$의 샘플은 각각 이동도 $29.52cm^2/V{\cdot}s$, $16.15cm^2/V{\cdot}s$, 문턱전압 2.61 V, 6.14 V, $S{\cdot}S$ 0.37 V/decade, 0.85 V/decade, on-off ratio 5.21 E+07, 1.10 E+07이었다. 30 sccm의 산소유량, 열처리 온도 $200^{\circ}C$에서 열처리 시간 1시간, 1시간 30분 샘플은 각각 이동도 $12.27cm^2/V{\cdot}s$, $10.15cm^2/V{\cdot}s$, 문턱전압 8.07 V, 4.21 V, $S{\cdot}S$ 0.89 V/decade, 0.71 V/decade, on-off ratio 4.31 E+06, 1.05 E+07이었다. 산화물 반도체의 열처리 효과 분석을 통하여 높은 열처리 온도, 적은 산소의 유량, 열처리 시간이 길수록 이동도, 문턱전압, $S{\cdot}S$의 산화물 박막 트랜지스터 소자의 전기적 특성이 개선되었다.