• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.390-390
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• 2012

Information technology industries has grown rapidly and demanded alternative memories for the next generation. The most popular random access memory, dynamic random-access memory (DRAM), has many advantages as a memory, but it could not meet the demands from the current of developed industries. One of highlighted alternative memories is magnetic random-access memory (MRAM). It has many advantages like low power consumption, huge storage, high operating speed, and non-volatile properties. MRAM consists of magnetic-tunnel-junction (MTJ) stack which is a key part of it and has various magnetic thin films like CoFeB, FePt, IrMn, and so on. Each magnetic thin film is difficult to be etched without any damages and react with chemical species in plasma. For improving the etching process, a high density plasma etching process was employed. Moreover, the previous etching gases were highly corrosive and dangerous. Therefore, the safety etching gases are needed to be developed. In this research, the etch characteristics of CoFeB magnetic thin films were studied by using an inductively coupled plasma reactive ion etching in $CH_4/O_2/Ar$ gas mixes. TiN thin films were used as a hardmask on CoFeB thin films. The concentrations of $O_2$ in $CH_4/O_2/Ar$ gas mix were varied, and then, the rf coil power, gas pressure, and dc-bias voltage. The etch rates and the selectivity were obtained by a surface profiler and the etch profiles were observed by a field emission scanning electron microscopy. X-ray photoelectron spectroscopy was employed to reveal the etch mechanism.

• Journal of the Korean institute of surface engineering
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• v.51 no.3
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• pp.139-148
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• 2018

In this study, surface analysis of Ni-Cr and Co-Cr alloys with addition of Ti and Mo for dental CAD/CAM use has been researched experimentally. The surface characteristics of the alloys were examined by Vickers hardness test, bonding strength test, surface roughness test, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction spectroscopy. The shrinkage of the sintered Ni-Cr alloy alloy was slightly larger than that of Ni-Cr-Ti alloy, and larger than Co-Cr alloy. Also, the addition of Mo showed a tendency to decrease shrinkage somewhat. From the result of XRD analysis, NiCr, $Ni_3Cr$ and $Ni_3Ti$ were observed in the sintered Ni-13Cr-xTi and Ni-13Cr-xMo alloys. In addition, ${\sigma}-CrCo$, $Co_2Mo_3$ and $TiCo_2$ were formed in the sintered Co-Cr-xTi and Co-Cr-xMo alloys. Surface hardness of Ti and Mo added alloy was higher than those of Ni-Cr and Co-Cr alloy. The bond strength between sintered alloy and porcelain was $16.1kgf/mm^2$ for Ni-13Cr alloy, $17.8kgf/mm^2$ for Ni-13Cr-5Ti alloy, and $8.2kgf/mm^2$ for Ni-13Cr-10Ti alloy, respectively.

• Journal of Periodontal and Implant Science
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• v.45 no.3
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• pp.94-100
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• 2015

Purpose: The aim of this study was to investigate the combined effects of physical and chemical surface factors on in vivo bone responses by comparing chemically modified hydrophilic sandblasted, large-grit, acid-etched (modSLA) and anodically oxidized hydrophobic implant surfaces. Methods: Five modSLA implants and five anodized implants were inserted into the tibiae of five New Zealand white rabbits (one implant for each tibia). The characteristics of each surface were determined using field emission scanning electron microscopy, energy dispersive spectroscopy, and confocal laser scanning microscopy before the installation. The experimental animals were sacrificed after 1 week of healing and histologic slides were prepared from the implant-tibial bone blocks removed from the animals. Histomorphometric analyses were performed on the light microscopic images, and bone-to-implant contact (BIC) and bone area (BA) ratios were measured. Nonparametric comparison tests were applied to find any significant differences (P<0.05) between the modSLA and anodized surfaces. Results: The roughness of the anodized surface was $1.22{\pm}0.17{\mu}m$ in Sa, which was within the optimal range of $1.0-2.0{\mu}m$ for a bone response. The modSLA surface was significantly rougher at $2.53{\pm}0.07{\mu}m$ in Sa. However, the modSLA implant had significantly higher BIC than the anodized implant (P=0.02). Furthermore, BA ratios did not significantly differ between the two implants, although the anodized implant had a higher mean value of BA (P>0.05). Conclusions: Within the limitations of this study, the hydrophilicity of the modSLA surface may have a stronger effect on in vivo bone healing than optimal surface roughness and surface chemistry of the anodized surface.

• Transactions on Electrical and Electronic Materials
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• v.11 no.2
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• pp.73-76
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• 2010

The copper indium disulfide ($CuInS_2$) thin film was manufactured using sputtering and thermal evaporation methods, and the annealing with sulfurization process was used in the vacuum chamber to the substrate temperature on the glass substrate, the annealing temperature and the composition ratio, and the characteristics thereof were investigated. The $CuInS_2$ thin film was manufactured by the sulfurization of a soda lime glass (SLG) Cu/In/S stacked [1] elemental layer deposited on a glass substrate by vacuum chamber annealing [2] with sulfurization for various times at a temperature of substrate temperature of $200^{\circ}C$. The structure and electrical properties of the film was measured in order to determine the optimum conditions for the growth of $CuInS_2$ ternary compound semiconductor $CuInS_2$ thin films with a non-stoichiometric composition. The physical properties of the thin film were investigated under various fabrication conditions [3,4], including the substrate temperature, annealing temperature and annealing time by X-ray diffraction (XRD), field Emission scanning electron microscope (FE-SEM), and Hall measurement systems. [5] The sputtering rate depending upon the DC/RF power was controlled so that the composition ratio of Cu versus In might be around 1:1, and the substrate temperature affecting the quality of the film was varied in the range of room temperature (RT) to $300^{\circ}C$ at intervals of $100^{\circ}C$, and the annealing temperature of the thin film was varied RT to $550^{\circ}C$ in intervals of $100^{\circ}C$.

• Korean Journal of Materials Research
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• v.23 no.11
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• pp.661-665
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• 2013

We investigated the characteristics of electroless plated Cu films on screen printed Ag/Anodized Al substrate. Cu plating was attempted using neutral electroless plating processes to minimize damage of the anodized Al substrate; this method used sodium hypophosphite instead of formaldehyde as a reducing agent. The basic electroless solution consisted of $CuSO_4{\cdot}5H_2O$ as the main metal source, $NaH_2PO_2{\cdot}H_2O$ as the reducing agent, $C_6H_5Na_3O_7{\cdot}2H_2O$ and $NH_4Cl$ as the complex agents, and $NiSO_4{\cdot}6H_2O$ as the catalyser for the oxidation of the reducing agent, dissolved in deionized water. The pH of the Cu plating solutions was adjusted using $NH_4OH$. According to the variation of pH in the range of 6.5~8, the electroless plated Cu films were coated on screen printed Ag pattern/anodized Al/Al at $70^{\circ}C$. We investigated the surface morphology change of the Cu films using FE-SEM (Field Emission Scanning Electron Microscopy). The chemical composition of the Cu film was determined using XPS (X-ray Photoelectron Spectroscopy). The crystal structures of the Cu films were investigated using XRD (X-ray Diffraction). Using electroless plating at pH 7, the structures of the plated Cu-rich films were typical fcc-Cu; however, a slight Ni component was co-deposited. Finally, we found that the formation of Cu film plated selectively on PCB without any lithography is possible using a neutral electroless plating process.

• Nuclear Engineering and Technology
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• v.51 no.8
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• pp.1964-1969
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• 2019

The safety and efficiency of nuclear reactors largely depend on the monitoring and control of nuclear radiation. Due to the unique nuclear-physical characteristics, Hf is one of the most promising materials for the manufacturing of the control rods and the emitters of neutron detectors. It is proposed to use the Compton neutron detector with the emitter made of Hf in the In-core Instrumentation System (ICIS) for monitoring the neutron field. The main advantages of such a detector in comparison the conventional β-emission sensors are the possibility of reaching of a higher cumulative radiation dose and the absence of signal delays. The response time of the detection is extremely important when a nuclear reactor is operating near its critical operational parameters. Taking Hf as an example, the general principles for calculating the chains of materials transformation under neutron irradiation are reported. The influence of ^179m1Hf on the Hf composition changing dynamics and the process of transmutants' (Ta, W) generation were determined. The effect of these processes on the absorbing properties of Hf, which inevitably predetermine the lifetime of the detector and its ability to generate a signal, is estimated.

• Korean Journal of Materials Research
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• v.27 no.1
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• pp.48-52
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• 2017

In this study, we used I-V spectroscopy, photoconductivity (PC) yield and internal photoemission (IPE) yield using IPE spectroscopy to characterize the Schottky barrier heights (SBH) at insulator-semiconductor interfaces of Pt/$HfO_2$/p-type Si metal-insulator-semiconductor (MIS) capacitors. The leakage current characteristics of the MIS capacitor were analyzed according to the J-V and C-V curves. The leakage current behavior of the capacitors, which depends on the applied electric field, can be described using the Poole-Frenkel (P-F) emission, trap assisted tunneling (TAT), and direct tunneling (DT) models. The leakage current transport mechanism is controlled by the trap level energy depth of $HfO_2$. In order to further study the SBH and the electronic tunneling mechanism, the internal photoemission (IPE) yield was measured and analyzed. We obtained the SBH values of the Pt/$HfO_2$/p-type Si for use in Fowler plots in the square and cubic root IPE yield spectra curves. At the Pt/$HfO_2$/p-type Si interface, the SBH difference, which depends on the electrical potential, is related to (1) the work function (WF) difference and between the Pt and p-type Si and (2) the sub-gap defect state features (density and energy) in the given dielectric.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.149-154
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• 2005

We fabricated Ni/Co(or Co/Ni) composite silicide layers on the non-patterned wafers from Ni(20 nm)/Co(20 nm)/poly-Si(70 nm) structure by rapid thermal annealing of $700{\~}1100^{\circ}C$ for 40 seconds. The sheet resistance, cross-sectional microstructure, and surface roughness were investigated by a four point probe, a field emission scanning electron microscope, and a scanning probe microscope, respectively. The sheet resistance increased abruptly while thickness decreased as silicidation temperature increased. We propose that the poly silicon inversion due to fast metal diffusion lead to decrease silicide thickness. Our results imply that we should consider the serious inversion and fast transformation in designing and process f3r the nano-height fully cobalt nickel composite silicide gates.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.1
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• pp.33-40
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• 2014

Poly vinylidene fluoride-co-hexafluoropropylene (PVdF-HFP) membrane were prepared by the electrospinning technique. We had applied a DLC coating process and then the surface of the membrane and the contact angle change was investigated. Electrospun fibrous PVdF-HFP membrane surface became to wrinkled shape by Ar plasma treatment and treatment conditions. The wrinkled surface of PVdF-HFP membrane became super-hydrophilic. However, after DLC coating process, it became super-hydrophobic. The resulting surfaces were characterized by water contact angle measurement, X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FE-SEM). Resultantly it was recognized that the wettability characteristics of the membrane surfaces depended on the chemical composition and surface morphology.

• Transactions on Electrical and Electronic Materials
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• v.16 no.3
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• pp.124-129
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• 2015

Organic electronics are the domain in which the components and circuits are made of organic materials. This new electronics help to realize electronic and optoelectronic devices on flexible substrates. In recent years, organic materials have replaced conventional semiconductors in many electronic components such as, organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs) and organic photovoltaic (OPVs). It is well known that organic light emitting diodes (OLEDs) have many advantages in comparison with inorganic light-emitting diodes LEDs. These advantages include the low price of manufacturing, large area of electroluminescent display, uniform emission and lower the requirement for power. The aim of this paper is to model polymer LEDs and OLEDs made with small molecules for studying the electrical and optical characteristics. The purpose of this modeling process is, to obtain information about the running of OLEDs, as well as, the injection and charge transport mechanisms. The first simulation structure used in this paper is a mono layer device; typically consisting of the poly (2-methoxy-5(2'-ethyl) hexoxy-phenylenevinylene) (MEH-PPV) polymer sandwiched between an anode with a high work function, usually an indium tin oxide (ITO) substrate, and a cathode with a relatively low work function, such as Al. Electrons will then be injected from the cathode and recombine with electron holes injected from the anode, emitting light. In the second structure, we replaced MEH-PPV by tris (8-hydroxyquinolinato) aluminum (Alq₃). This simulation uses, the Poole-Frenkel -like mobility model and the Langevin bimolecular recombination model as the transport and recombination mechanism. These models are enabled in ATLAS- SILVACO. To optimize OLED performance, we propose to change some parameters in this device, such as doping concentration, thickness and electrode materials.