• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.276-276
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• 2013

Time-Of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) and Atomic Force Microscopy (AFM) are the useful instruments to measure nanostructures of material surfaces. Surface pattern formation in blending homopolymer and diblock copolymer films was investigated as a function of film thickness and annealing conditions. In this study, surface structures of blending homopolymer [deuterated polystyrene (Mn 20,000), poly (methyl methacrylate) (Mn 18,000)] and diblock copolymer [Poly (deuteratedstyrene(d8)-b-methyl methacrylate) (Mn 19,500-18,100)] films were observed. The AFM result indicated that the nanostructures and film thickness depended on temperature, concentration and solvent. TOF-SIMS depth profiling was obtained for the lamellar morphology of symmetric dPS-b-PMMA which is found to orient parallel to the surface of the substrate. Elemental and molecular depth profiles measured in the negative ion mode by a Cs+ primary ion beam demonstrate variations in hydrogen, deuterium, carbon, oxygen, hydrocarbons and deuterated hydrocarbons within the diblock copolymer according to the depth.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.5
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• pp.456-461
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• 2007

In this study, a surface treatment method using accelerated Ar ions was experimented for exposing the carbon nanotubes (CNT) from the screen-printed CNT paste. After making a cathode electrode on the glass substrate, photo sensitive CNT paste was screen-printed, and then back-side was exposed by UV light. Then, the exposed CNT paste was selectively remained by development. After post-baking, the remained CNT paste was bombarded by accelerated Ar ions for removing some binders and exposing only CNTs. As results, the field emission characteristics were strongly depended on the accelerating energy, bombardment time, and the power of RF plasma ion source. When Ar ions accelerated with 100 eV energy from the 100 W RF plasma source are bombarded on the CNT paste surface for 10 min, the emission level and the uniformity were best.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.453-454
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• 2006

We studied the nematic liquid crystal (NLC) alignment capability by the IB(Ion bean) alignment method on a NDLC(Nitrogen Diamond Like Carbon) as a-C:H thin film. and investigated electro-optical performances of the IBaligned IPS(In plane switching)cell with NDLC surface. A good LC alignment by IB exposure on a NDLC surface was achieved. Monodomain alignment of the IB aligned IPS cell can be observed. The goodelectro-optical (EO) characteristics of the IB aligned IPS cell was observed with oblique IBexposure on the NDLC as a-C:H thin film for 1 min.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.429-429
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• 2007

For various applications of liquid crystal displays (LCDs), the uniform alignment of liquid crystal (LC) molecules on treated surfaces is significantly important. Generally, a rubbing method has been widely used to align the LC molecules on polyimide (PI) surfaces. Rubbed PI surfaces have suitable characteristics, such as uniform alignment. However, the rubbing method has some drawbacks, such as the generation of electrostatic charges and the creation of contaminating particles. Thus, we strongly recommend a non contact alignment technique for future generations of large high-resolution LCDs. Most recently, the LC aligning capabilities achieved by ultraviolet and ion-beam exposures which are non contact methods, on diamond-like carbon (DLC) inorganic thin film layers have been successfully studied because DLC thin films have a high mechanical hardness, a high electrical resistivity, optical transparency, and chemical inertness. In addition, nitrogen-doped DLC (NDLC) thin films exhibit properties similar to those of the DLC thin films and a higher thermal stability than the DLC thin films because C:N bonding in the NDLC thin filmsis stronger against thermal stress than C:H bonding in the DLC thin films. Our research group has already studied the NDLC thin films by an ion-beam alignment method. The $SiN_x$ thin films deposited by plasma-enhanced chemical vapor deposition are widely used as an insulation layer for a thin film transistor, which has characteristics similar to those of DLC inorganic thin films. Therefore, in this paper, we report on LC alignment effects and pretilt angle generation on a $SiN_x$, thin film treated by ion-beam irradiation for various N ratios

• Progress in Medical Physics
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• v.26 no.1
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• pp.12-17
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• 2015

The purpose of the Monte Carlo simulation study was to provide the optimized nozzle design to satisfy the beam conditions for biomedical researches in the Korean heavy-ion accelerator, RAON. The nozzle design was required to produce $C^{12}$ beam satisfying the three conditions; the maximum field size, the dose uniformity and the beam contamination. We employed the GEANT4 toolkit in Monte Carlo simulation to optimize the nozzle design. The beams for biomedical researches were required that the maximum field size should be more than $15{\times}15cm^2$, the dose uniformity was to be less than 3% and the level of beam contamination due to the scattered radiation from collimation systems was less than 5% of total dose. For the field size, we optimized the tilting angle of the circularly rotating beam controlled by a pair of dipole magnets at the most upstream of the user beam line unit and the thickness of the scatter plate located downstream of the dipole magnets. The values of beam scanning angle and the thickness of the scatter plate could be successfully optimized to be $0.5^{\circ}$ and 0.05 cm via this Monte Carlo simulation analysis. For the dose uniformity and the beam contamination, we introduced the new beam configuration technique by the combination of scanning and static beams. With the combination of a central static beam and a circularly rotating beam with the tilting angle of $0.5^{\circ}$ to beam axis, the dose uniformity could be established to be 1.1% in $15{\times}15cm^2$ sized maximum field. For the beam contamination, it was determined by the ratio of the absorbed doses delivered by $C^{12}$ ion and other particles. The level of the beam contamination could be achieved to be less than 2.5% of total dose in the region from 5 cm to 17 cm water equivalent depth in the combined beam configuration. Based on the results, we could establish the optimized nozzle design satisfying the beam conditions which were required for biomedical researches.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.134-137
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• 2008

The effects of residual stress and surface defects on the mechanical properties of the high carbon steel filament used for the automotive tire have been experimentally investigated. The samples were fabricated with annealing temperature. The residual stress was measured by focused ion beam and strain mapping software which has advantages, such as data with high accuracy and fast data acquisition time. Mechanical properties, such as tensile strength and fatigue resistance, were gradually increased up to $200^{\circ}C$ and then slightly decreased. From the measurement of residual stress and level of surface defect, it was revealed that the critical factor was varied with different temperature region. That is, the fatigue resistance increased due to decreasing the residual stress and decreased due to increasing the size and distribution of surface defect.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.3 s.192
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• pp.134-139
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• 2007

We report the suspension of individual multi-walled carbon nanotubes (MWNTs) from the bottom substrate using deep trench electrodes that were fabricated using optical lithography. During drying of the solution in dielectrophoretic assembly, the capillary force pulls the MWNT toward the bottom substrate, and it then remains as a deformed structure adhering to the bottom substrate after the solution has dried out. Small-diameter MWNTs cannot be suspended using thin electrodes with large gaps, but large-diameter MWNTs can be suspended using thicker electrodes. We present the statistical experimental results for successful suspension, as well as the feasible conditions for a MWNT suspension based on a theoretical approach.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.238.1-238.1
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• 2005

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.203-203
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• 2012

The SWCNTs network are formed on various plastic substrates such as poly(ethylene terephthalate) (PET), polyimide (PI) and soda lime glass using roll-to-roll printing and spray process. Selective patterning of carbon nanotubes film on transparent substrates was performed using a femtosecond laser. This process has many advantages because it is performed without chemicals and is easily applied to large-area patterning. It could also control the transparency and conductivity of CNT film by selective removal of CNTs. Furthermore, selective cutting of carbon nanotube using a femtosecond laser does not cause any phase change in the CNTs, as usually shown in focused ion beam irradiation of the CNTs. The patterned SWCNT films on transparent substrate can be used electrode layer for touch panels of flexible or flat panel display instead indium tin oxide (ITO) film.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.330-333
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• 2005

We investigated the liquid crystal (LC) alignment phenomena using a-C:H and a-C:F:H thin films. Homogeneous alignment is obtained using ion beam treated hydrogenated amorphous carbon (a-C:H) thin films. Homeotropic alignment is obtained using F treated a-C:H thin films, namely, fluorinated amorphous carbon (a-C:F:H) thin films. We investigated the relationship between the surface properties of amorphous carbon based alignment layer and LC alignment phenomena.