• Journal of the Korean Applied Science and Technology
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• v.16 no.1
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• pp.33-40
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• 1999

We used Cu as a representative of metals to be directly adsorbed on the bare Si surface and studied its removal DHF, DHF-$H_2O_2$ and BHF solution. It has been found that Cu ion in DHF adheres on every Si wafer surface that we used in our study (n, p, n+, p+) especially on the n+-Si surface. The DHF-$H_2O_2$ solution is found to be effective in removing metals featuring high electronegativity such as Cu from the p-Si and n-Si wafers. Even when the DHF-$H_2O_2$ solution has Cu ions at the concentration of 1ppm, the solution is found effective in cleaning the wafer. In the case the n+-Si and p+-Si wafers, however, their surfaces get contaminated with Cu When Cu ion of 10ppb remains in the DHF-$H_2O_2$ solution. When BHF is used, Cu in BHF is more likely to contaminate the n+-Si wafer. It is also revealed that the surfactant added to BHF improve wettability onto p-Si, n-Si and p+-Si wafer surface. This effect of the surfactant, however, is not observed on the n+-Si wafer and is increased when it is immersed in the DHF-$H_2O_2$ solution for 10min. The rate of the metallic contamination on the n+-Si wafer is found to be much higher than on the other Si wafers. In order to suppress the metallic contamination on every type of Si surface below 1010atoms/cm2, the metallic concentration in ultra pure water and high-purity DHF which is employed at the final stage of the cleaning process must be lowered below the part per trillion level. The DHF-$H_2O_2$ solution, however, degrades surface roughness on the substrate with the n+ and p+ surfaces. In order to remove metallic impurities on these surfaces, there is no choice at present but to use the $NH_4OH-H_2O_2-H_2O$ and $HCl-H_2O_2-H_2O$ cleaning.

• Resources Recycling
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• v.19 no.4
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• pp.51-57
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• 2010

As a recycling of Si sludge from Si wafer process, a Si-SiC-CuO-C composite material was synthesized and investigated as an anode material for lithium batteries. The Si sludge consisted of Si, SiC, machine oil, and metallic impurities. The oil and metal impurities was removed by organic washing, magnetic separation, and acid washing. The Si-SiC-CuO-C composite from the recovered Si-SiC mixture was prepared by high-energy mechanical milling. According to the electrochemical tests such as charge-discharge capacity and cycling behavior, it showed the improved cycle performance. The SiC and CuO-related phases were presumed to restrain the volume expansion of the anode and Fe, however, should be removed below 10 ppm prior to synthesis of the composite because it caused the capacity loss of the active material itself.

• Environmental Engineering Research
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• v.20 no.1
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• pp.89-97
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• 2015

Remediation of wastewater contaminated with metal(II)-complexed species (Cu(II)-NTA (NTA: nitrilotriacetic acid), Cu(II)-EDTA (EDTA: ethylenediamine tetraacetic acid) and Cd(II)-EDTA is attempted using the potential applicability of ferrate(VI). Kinetics of pollutant degradation is obtained with the removal of ferrate(VI) studied at wide range of pH (8.0-10.0) and the concentration of metal(II)-complexed species (0.3 to 15.0 mmol/L) employing a constant dose of ferrate(VI) i.e., 1.0 mmol/L. Pseudo-first-order and pseudo-second-order rate constants were obtained in the reduction of ferrate(VI) which was then employed to obtain the overall rate constants of the pollutant degradation. The mineralization of NTA and EDTA was obtained with the change in TOC (total organic carbon) values collected by the ferrate(VI) treated pollutant samples. Decrease in pH and molar pollutant concentrations was greatly favored the percent mineralization of NTA or EDTA by the ferrate(VI) treatment. The treated pollutant samples were filtered and subjected for AAS (atomic absorption spectrophotometric) analysis to assess the simultaneous removal of copper and cadmium from aqueous solutions at the studied pH as well at the elevated pH 12.0. Results show that an enhanced removal of cadmium or copper was achieved at pH 12.0. Overall, ferrate(VI) possesses multifunctional application in wastewater treatment as it oxidizes the degradable impurities and removes metallic impurities by coagulation process.

• Journal of Conservation Science
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• v.37 no.6
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• pp.738-747
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• 2021

This study attempted to investigate the metallurgical characteristic through material scientific analysis of hammer scale produced as a direct smelting method restoration experiment for each raw material of iron. To this end, four hammer scale groups were set up, respectively, by experimenting with Gyeongju-Gampo Iron sand and Yangyang Iron ore. For the analysis, principal component analysis, compound analysis, microstructure observation, and chemical composition were confirmed. As a result of principal component analysis, as forging and refining progressed, the content of Fe increased and the content of non-metallic objects decreased. As a result of compound analysis, iron oxide-based compounds were identified. As a result of confirming microstructure and chemical composition, Wüstite and Fayalite were observed overall, and agglomerated Wüstite were observed in some. Magnetite on shape of polygon and pillar was observed. In addition, it was confirmed that internal defects, impurities, and non-metallic interventions gradually decreased. In the future, it is necessary to investigate the metallurgical characteristic through material scientific analysis of hammer scale produced through restoration experiments using various raw material of iron, and compare them with those excavated from Iron manufacture ruins.

• Korean Journal of Materials Research
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• v.8 no.8
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• pp.751-756
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• 1998

Effects of remote hydrogen plasma cleaning process parameters on the removal of Fe impurities on Si surfaces and the Fe removal mechanism were investigated. Fe removal efficiency is enhanced with decreasing the plasma exposure time and increasing the rf-power. The optimum plasma exposure time and rf-power are 1 min and 100W. respectively, in the range below 10 min and 100W. Fe removal efficiency is better under lower pressures than higher pressures, and the optimum $\textrm{H}_2$ flow rate was found to be 20 and 60sccm, respectively, under a low and a high pressure. The post-RHP(remote hydrogen plasma) annealing enhanced metallic contaminants removal efficiency, and the highest efficiency was achieved at $600^{\circ}C$. According to the AFM analysis results Si surface roughness was improved by 30-50%, which seems to be due to the removal of particles by the plasma cleaning. Also. Fe impurities removal mechanisms by remote hydrogen plasma are discussed.

• Resources Recycling
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• v.25 no.4
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• pp.42-48
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• 2016

A research for the recovery of the metal with high purity from the waste tin plating solution was carried out. First, tin plating waste solution was tested to remove the organic substances and metallic impurities such as Fe, Zn, Na etc. using ion exchange resin having iminodiacetic functional groups (Lewatit TP 207). Second, the tin solution was purified to obtain the high purity tin solution using ion exchange resin having ethylhexyl-phosphate functional groups (Lewatit VPOC 1026). Finally, 99.98% of the high purity of tin metal can be recovered from the purified solution by cyclone type electrowinning method.

• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.618-622
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• 2010

Cost-effective purification methods of silicon were carried out in order to replace the conventional Siemens method for solar grade silicon. Firstly, acid leaching which is a hydrometallurgical process was preceded with grinded silicon powders of metallurgical grade (~99% purity) to remove metallic impurities. Then, plasma treatments were performed with the leached silicon powders of 99.94% purity by argon plasma at 30 kW power under atmospheric pressure. Plasma treatment was specifically efficient for removing Zr, Y, and P but not for Al and B. Another purification step by EB treatment was also studied for the 99.92% silicon lump which resulted in the fast removal of boron and aluminum. That means the two methods are effective alternative tools for removing the doping elements like boron and phosphor.

• Korean Journal of Materials Research
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• v.6 no.7
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• pp.661-670
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• 1996

리모트 수소 플라즈마를 이용하여 실리콘 웨이퍼 표면 위에 있는 금속불순물의 제거 및 제거기구에 관하여 조사하였다. 실리콘의 표면과 내부분석을 위하여 TXRF(total reflection x-ray fluorescence)와 SPV(surface photovoltage), AFM(atomic force microscope)을 사용하였다. TXRF 분석결과 리모트 수소 플라즈마가 금속오염물질 제거에 상당한 효과가 있는 것으로 나타났다. TXRF분석결과 리모트 수소 플라즈마가 금속오염물질 제거에 상당한 효과가 있는 것으로 나타났다. 리모트 수소플라트마 처리 후 금속오염은 금속원소의 종류에 따라 1010atoms/$\textrm{cm}^2$-1011atoms/$\textrm{cm}^2$수준이었다. SPV분석결과를 보면 수소 플라즈마 처리에 의해 minority carrier 수명이 전반적으로 증가하였다. AFM 분석을 통하여 수소 플라즈마 처리가 표면 손상을 일으키지 않으며 표면의 거칠기에 나쁜 영향을 미치지 않음을 알 수 있었다. 또한 본 실험에서 나타난 결과들을 종합해 볼 때 금속오염물의 제거기구는 자연산화막 혹은 수소로 passivate된 실리콘 웨이퍼 표면을 수소 플라즈마에서 발생된 수소원자가 실리콘표면을 약하게 에칭할 때 떨어져 나가는 'lift-off'가 유력한 것으로 판단된다.

• Electrical & Electronic Materials
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• v.8 no.2
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• pp.176-183
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• 1995

The present work is concerned with the switching conduction characteristics of PI LB films in metal insulator metal sandwiches. By applying various DC voltage bias to MIM junctions, conduction characteristics of junctions can be changed between the high-voltage low-current(off) condition, the low-voltage high-current (on) condition and the medium(mid) condition. Switching conduction characteristics can be also observed in MIM junctions employing some aromatic compounds as insulators. Switching conduction characteristics is assumed to be owing to the existence of aromatic rings, space charge in films, impurities on metal-insulator interface, and difference in work functions of base and top electrodes metal. To study the conduction process of on, off, and mid conductions, we measured I-V, d$^{2}$V/d I$^{2}$-V characteristics of junctions with several different top electrodes under various temperatures. Small conductance changes of junctions can be measured by observing the second derivative, d$^{2}$V/dI$^{2}$, of I-V curve. A dynamical technique is used to get the second derivatives. That is, a finite modulation of the current is applied to the junctions and the second harmonic of the voltage is detected.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.5
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• pp.402-410
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• 2008

Single-walled carbon nanotubes (SWCNTs) were currently produced together with some contaminants such as a metallic catalyst, amorphous carbon, and graphitic nanoparticles, which should be sometimes purified for their applications. This study aimed to develop efficient, scalable purification processes but less harmful to SWCNTs. We designed three-step purification processes: acidic treatment, surface functionalization and soxhlet extraction, and heat treatment. During the soxhlet extraction using tetrahydrofuran, specifically, carbon impurities could be easily expelled through a glass thimble filter without any significant loss of CNTs. Finally, SWCNTs were left as a bulky paper on the filter through membrane filtration. Vertically aligned SWCNTs on one side of bulky paper were well developed in a speparation from the filter paper, which were formed by being sucked through the filter pores during the pressurized filtration. The bucky paper showed a very high peak current density of field emission up to $200\;mA/cm^2$ and uniform field emission images on phosphor, which seems very promising to be applied to vacuum microelectronics such as microwave power amplifiers and x-ray sources.