• Journal of Information Display
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• v.2 no.4
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• pp.57-62
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• 2001

Green-emitting $Zn_2SiO_4$:Mn phosphor particles having a spherical shape and high luminescence intensities under VUV were prepared by spray pyrolysis process under severe preparation conditions. The type of precursor solutions affected the morphology and luminescence characteristics of the prepared particles. The particles prepared from the clear solution by laboratory-scale process had spherical shape and dense morphology, while the particles prepared from the severe preparation conditions had rough surface and collapsed structure. However, the particles prepared from the colloidal solution utilizing fumed silica were spherical in shape and filled morphology at the severe preparation conditions of high flow rate of carrier gas, high concentration of solution, and large reactor size. The prepared $Zn_2SiO_4$:Mn phosphor particles with complete spherical shape had higher photoluminescence intensity than that of the commercial product prepared by solid state reaction.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.323-323
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• 2010

Saw damage of crystalline silicon wafer is unavoidable factor. Usually, alkali treatment for removing the damage has been carried out as the saw damage removal (SDR) process for priming the alkali texture. It usually takes lots of time and energy to remove the sawed damages for solar grade crystalline silicon wafers We implemented two different mixed acidic solution treatments to obtain the improved surface structure of silicon wafer without much sacrifice of the silicon wafer thickness. At the first step, the silicon wafer was dipped into the mixed acidic solution of $HF:HNO_3$=1:2 ration for polished surface and at the second step, it was dipped into the diluted mixed acidic solution of $HF:HNO_3:H_2O$=7:3:10 ratio for porous structure. This double treatment to the silicon wafer brought lower reflectance (25% to 6%) and longer carrier lifetime ($0.15\;{\mu}s$ to $0.39\;{\mu}s$) comparing to the bare poly-crystalline silicon wafer. With optimizing the concentration ratio and the dilution ratio, we can not only effectively substitute the time consuming process of SDR to some extent but also skip plasma enhanced chemical vapor deposition (PECVD) process. Moreover, to conduct alkali texture for pyramidal structure on silicon wafer surface, we can use only nitric acid rich solution of the mixed acidic solution treatment instead of implementing SDR.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.824-827
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• 2000

Fabrication of InP-based photonic devices by dry etch Process is important for clear formation of waveguide mesa structure. We have developed more efficient etch process of the inductively coupled plasma (ICP) with low damages and less polymeric deposits for the InP-based photonic devices than the reactive ion etching (RIE) technique. We report the tendency of etch rate variation by the process parameters of the RF power, pressure, gas flow rate, and the gas mixing ratio. The surface roughness of InP-based waveguide structure was more improved by the light wet etching in the mixed solution of H$_2$SO$_4$:H$_2$O (1:1)

• Journal of the Korean institute of surface engineering
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• v.54 no.6
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• pp.340-347
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• 2021

Among various metal oxide semiconductors, ZnO has an excellent electrical, optical properties with a wide bandgap of 3.3 eV. It can be applied as a photocatalytic material due to its high absorption rate along with physical and chemical stability to UV light. In addition, it is important to control the morphology of ZnO because the size and shape of the ZnO make difference in physical properties. In this paper, we demonstrate synthesis of size-controlled ZnO tetrapods using an atmospheric pressure plasma system. A micro-sized Zn spherical powder was continuously introduced in the plume of the atmospheric plasma jet ignited with mixture of oxygen and nitrogen. The effect of plasma power and collection sites on ZnO nanostructure was investigated. After the plasma discharge for 10 min, the produced materials deposited inside the 60-cm-long quartz tube were obtained with respect to the distance from the plume. According to the SEM analysis, all the synthesized nanoparticles were found to be ZnO tetrapods ranging from 100 to 600-nm-diameter depending on both applied power and collection site. The photocatalytic efficiency was evaluated by color change of methylene blue solution using UV-Vis spectroscopy. The photocatalytic activity increased with the increase of (101) and (100) plane in ZnO tetrapods, which is caused by enhanced chemical effects of plasma process.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.77-77
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• 2011

These days, a growing demand for memory device is filled up with the flash memory and the dynamic random access memory (DRAM). Although DRAM is a reasonable solution for current demand, the universal novel memory with high density, high speed and nonvolatility, needs to be developed. Among various new memories, the magnetic random access memory (MRAM) device is considered as one of good candidate memories because of excellent features including high density, high speed, low operating power and nonvolatility. The etching of MTJ stack which is composed of magnetic materials and insulator such as MgO is one of the vital process for MRAM. Recently, MgO has attracted great interest in the MTJ stack as tunneling barrier layer for its high tunneling magnetoresistance values. For the successful realization of high density MRAM, the etching process of MgO thin films should be investigated. Until now, there were some works devoted to the investigations on etch characteristics of MgO thin films. Initially, ion milling was applied to the etching of MgO thin films. However, ion milling has many disadvantages such as sidewall redeposition and etching damage. High density plasma etching containing the magnetically enhanced reactive ion etching and high density reactive ion etching have been employed for the improvement of etching process. In this work, inductively coupled plasma reactive ion etching (ICPRIE) system was adopted for the improvement of etching process using MgO thin films and etching gas mixes of $CH_4$/Ar and $CH_4$/$O_2$/Ar have been employed. The etch rates are measured by a surface profilometer and etch profiles are observed using field emission scanning emission microscopy (FESEM). The effects of gas concentration and etch parameters such as coil rf power, dc-bias voltage to substrate, and gas pressure on etch characteristics will be systematically explored.

• Journal of the Korean Vacuum Society
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• v.17 no.2
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• pp.113-116
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• 2008

As the integration in semiconductor display develops, semiconductor process becomes multilayer. In order to form several layer patterns, etching process which uses photoresistor (PR) must be performed in multilayer process. Repeated etching processes which take long time and PR residue cause mortal problems in semiconductor. To overcome such problems, we studied about the solution which eliminates PR effectively by using normal dry and wet etching method using plasma activated PR strip solvent in liquid condition. At first, we simulate the device which activates the plasma and make sure whether gas flow in device is uniform or not. Under activated plasma, etching effect is elevated. This improvement reduces etching time as well as display production time of semiconductor process. Generally, increasing etching process increases environmental hazards. Reducing etching process can save the etchant and protect environment as well.

• Journal of Adhesion and Interface
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• v.4 no.2
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• pp.10-20
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• 2003

This paper is relative to the electroless deposition of nickel or copper films on polyimide and polytetrafluoroethylene substrates. First, it is presented an original approach of the electroless process which consists in grafting nitrogenated functionalities on the polymer surfaces via plasma or VUV-assisted treatments operating in a nitrogen-based atmosphere ($NH_3$, $N_2$), and then in catalysing the grafted surfaces in an aqueous tin-free, Pd(+2)-based solution. Adhesion of the Pd(+2) catalytic species on polymer surfaces is explained by the formation of strong covalent bonds between these species and the grafted nitrogenated groups. Second, it is show how a fragmentation test performed in conjunction with electrical measurements can be used to characterize the practical adhesion of the electroless coatings deposited on flexible polymer substrates, and to evidence the influence of some experimental parameters (plasma treatment time and nature of the gas phase).

• Journal of the Korean institute of surface engineering
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• v.50 no.5
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• pp.366-372
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• 2017

Plasma electrolytic oxidation(PEO) has attracted attention as a surface treatment which has high wear resistance and corrosion resistance. PEO is generally considered as cost-effective, environmentally friendly and superior in terms of coating performance. Most of studies about the PEO processes have been applied to light metals such as Al and Mg. Because the strength of Al and Mg is weaker than that of steel, there is a limit to the application. In this study, PEO process was used to form oxide coatings on Hot dipped aluminized(HDA) steel and the characteristics of the coating film according to the PEO current density were studied. The morphology was observed by SEM and component was analyzed by using EDS. The corrosion behaviors of PEO coating films were estimated by exposing salt spray test at 5 wt.% NaCl solution and measuring polarization curves in deaerated 3 wt.% NaCl solution. With the increase of PEO process current density, the pore size of the coating surface and the thickness of coating increased. It was confirmed that no Fe component was present on the coating surface. PEO coating films obviously showed good corrosion resistance compared with HDA. It is considered that the PEO coating acts as a barrier to protect the base material from external factors causing corrosion.

• Journal of the Korea Institute of Building Construction
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• v.21 no.6
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• pp.539-550
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• 2021

In this study, Zn and Zn-15Al were coated on general carbon steel by plasma arc metal spraying and then immersed in a 3.5wt.% NaCl solution similar to the seawater environment to evaluate the corrosion resistance properties. Through the surface shape analysis test by SEM and XRD, it was found that the Zn coating was porous and needle-shaped, so the penetration of the electrolyte was easy, and thus the corrosion rate was rapid. On the other hand, the Zn-15Al coating had a uniform and dense shape and was shown to suppress corrosion.

• Membrane Journal
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• v.19 no.1
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• pp.54-62
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• 2009

Pervaporation membrane for butanol separation was prepared by hybrid process. Plasma treatment of commercial poly(dimethylsiloxane) (PDMS) membrane was attempted and combination of plasma treatment and PDMS solution coating on polysulfone, poly(ether imide) supports were also performed. Plasma treatment of PDMS membrane with hexane and silane group compounds was performed to increase the hydrophobicity of the surface, which enhanced the separation factor upto 12.5 at the expense of flux decrease down to $1.15kg/m^2{\cdot}hr$. Contact angle and relative sorption ratio were also related with hydrophobicity of the memrbane. Increase of PDMS prepolymer composition resulted in dense structure of coating layer with better separation factor. Effects of sequence of PDMS coating vs. plasma treatment were examined. It was found that plasma treatment with butanol and n-hexane plasma followed by PDMS coating showed better performance and vice versa for plasma treatment with hexamethyldisilane and hexamethyldisilazane.