• E2M - 전기 전자와 첨단 소재
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• 제10권5호
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• pp.461-466
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• 1997

In this paper, we developed the new non-rubbing liquid crystal (LC) alignment techniques in the cell with slanted non-polarized ultraviolet (UV) light irradiation on polyimide (PI) film. It is shown that the uniform alignment for nematic (N) LC is obtained by using slanted non-polarized UV light irradiation on PI surface. We successfully obtained that the pretilt angle of NLC is generated about 3.3 degree in the cell with slanted non-polarized UV light irradiation with 70 degree on PI surface, for the first time. It is considered that the pretilt angle generation in NLC is attributed to interaction between the LC molecular and the PI, which is broken the polymer by slanted non-polarized UV irradiation. Therefore, we concluded that the uniform LC alignment is attributed to anisotropic dispersion force due to photo depolymerization with slanted non-polarized UV light irradiation on PI surface.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.951-954
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• 2001

We investigated the aligning capabilities for nematic liquid crystal (NLC) using a in-situ photodimerization method on various photopolymer surfaces. High Pretilt angle of the NLC can be measured by obliquely polarized UV exposure of 30$^{\circ}$on a photo-crosslinkable polyimide (PI) based polymer surface for 3 min. The pretilt angle of the NLC generated on the photopolymer surface using the in-situ photodimerization method was higher than that of a blending photopolymers (PI and cinnamate materials).

• 한국전기전자재료학회논문지
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• 제11권6호
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• pp.477-480
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• 1998

In this paper, we investigated the liquid crystal(LC) alignment and generation of pretilt angle by using photo-alignment techniques on two kinds of polyimide(PI) surface, It was found that the uniform alignment for nematic(N) LC is obtained in a cell with slanted UV light irradiation on PI surface without side chain. We successfully observed that the pretilt angle of NLC is generated about $3^{\circ}$ with an incident angle of 70 degree on the PI surface without side chain. It is considered that the pretilt angle generation in NLC is attributed to interaction between the LC molecules and the polymer surfaces.

• Transactions on Electrical and Electronic Materials
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• 제3권2호
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• pp.1-5
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• 2002

Alignment effects for nematic liquid crystal (NLC) and electro-optical (EO) characteristics of the ion beam (IB) aligned twisted nematic (TN)-liquid crystal display (LCD) with oblique ion beam exposure on the diamond-like carbon (DLC) thin film surface were studied. A high pretilt angle of 3.5$^{\circ}$ in NLC by ion beam exposure on the DLC thin film layer can be measured. An excellent voltage-transmittance (V-T) curve of the ion beam aligned TN-LCD was observed with oblique ion beam exposure on the DLC thin film surface for 1 min. Also, a faster response time for the ion beam aligned TN-LCD with oblique ion beam exposure on the DLC thin film surface for 1 min can be achieved.

• Journal of the Optical Society of Korea
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• 제20권1호
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• pp.125-129
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• 2016

In this study, we have investigated a high-temperature AlN nucleation layer and AlGaN epilayers on c-plane sapphire substrate by low-pressure metal-organic chemical vapor deposition (LP-MOCVD). High resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), scanning electron microscope (SEM) and Raman scattering measurements have been exploited to study the crystal quality, surface morphology, and residual strain of the HT-AlN nucleation layer. These analyses reveal that the insertion of an LT-AlN nucleation layer can improve the crystal quality, smooth the surface morphology of the HT-AlN nucleation layer and further reduce the threading dislocation density of AlGaN epifilms. The mechanism of inserting an LT-AlN nucleation layer to enhance the optical properties of HT-AlN nucleation layer and AlGaN epifilm are discussed from the viewpoint of driving force of reaction in this paper.

• 한국결정성장학회지
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• 제9권4호
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• pp.441-445
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• 1999

Thick diamond film having $~700\mu\textrm{m}$ thickness was deposited on polycrystalline molybdenum(Mo) substrate using high power (4 kW) microwave plasma-enhanced chemical vapor depostion (MPECVD) system. We could achieve free-standing diamond film via detaching as-deposited diamond film from the substrate by rapid cooling them under vacuum. We investigated the variation of photoconductivity after exposing the film surface to either oxygen or hydrogen plasma. At as-grown state, the growth side (the as-grown surface of the film) showed noticeable photoconcuctivity. The oxygen plasma treatment of this side led to the insulator. After exposing the film surface to hydrogen plasma, on the other hand, we could observe the reappearing of photoconductivity at the growth side. Based on these results, we suggest that the hydrogen plasma treatment may enhance the photoconductivity of free-standing diamond film.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.117-120
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• 2001

A new photoalignment material PFCPMI, poly[4-(fluorocinnamate)phenylmaleimide], was synthesized and the nematic liquid crystal (NLC) aligning capabilities on the photopolymer surface. The NLC pretilt angle generated by non-UV filter method on the PFCPMI surface was higher than that of the UV filter method. A good LC alignment by non-UV filter method was observed at $150^{\circ}C$ of annealing temperature. However, the alignment defect of the NLC by UV filter method was measured above $150^{\circ}C$ of annealing temperature. Consequently, the high pretilt angle and the good LC alignment in NLC using non-UV filter method can be acheived.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.346-349
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• 2001

We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of diamond like carbon (DLC) thin film. A high pretilt angle of about $4^{\circ}$ was measured by ion beam(IB) exposure on the DLC thin film surface. A good LC alignment was observed by the IB alignment method on the DLC thin film surface at annealing temperature of $200^{\circ}C$, and the alignment defect of the NLC was observed above annealing temperature of $220^{\circ}C$. Consequently, the high NLC pretilt angle and the good thermal stability of LC alignment can be achieved by the IB alignment method on the DLC thin film surface.

• 한국전기전자재료학회논문지
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• 제17권4호
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• pp.439-442
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• 2004

In this study, we investigated about electrooptics characteristic of three kinds of TN cell on the polyimide surface. Monodomain alignments of thermal stressed TN cell over temperature of liquid crystal isotropic phase were almost the same as that of no thermal stressed TN cells. However, the thermal stressed TN cells have many defects. Also, threshold voltage and response time of thermal stressed TN cells show the same performances as no thermal stressed TN cells. There were little changes of value in these TN cells. However, transmittances of TN cells on the polyimide surface decrease with increasing thermal stress time. Finally, the residual DC voltage of the thermal stressed TN cell on the polyimide surface shows decrease of characteristics as increasing thermal stress time. Therefore, the thermal stability of TN cell was decreased by high thermal stress for the long times.

• 한국결정성장학회지
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• 제22권6호
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• pp.269-273
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• 2012

Ammonia decomposition over titanium carbides were investigated using eight different samples which have been synthesized by TPR (temperature-programmed reduction) method of titanium oxide ($TiO_2$) with pure $CH_4$. The resulting materials which were synthesized using wo different heating rates and space velocity exhibited the different surface areas. These results indicated that the structural properties of these materials have been related to heating rates and space velocity employed. The titanium carbides prepared in this study proved to be active for ammonia decomposition, and the activity changed with the particle size/surface area. These showed the relationship between ammonia decomposition activity and the different active species. Compared to molybdenum carbide, the titanium carbides were one order of magnitude less active, suggesting the correlation between the activity difference and the degree of electron transfer between metals and carbon in metal carbides.