HVPE를 이용하여 r-plane 사파이어 위에 multi-step으로 성장시킨 a-plane GaN 에피층의 특성 연구

이원준,박미선,장연숙,이원재,하주형,최영준,이혜용,김홍승,Lee, Won-Jun,Park, Mi-Seon,Jang, Yeon-Suk,Lee, Won-Jae,Ha, Ju-Hyung,Choi, Young-Jun,Lee, Hae-Yong,Kim, Hong-Seung 한국결정성장학회 2016 한국결정성장학회지 Vol.26 No.3

본 연구에서는 HVPE(Hydride Vapor Phase Epitaxy)를 이용하여 각각 다른 V/III ratio를 가지는 multi-step의 성장 시간 변화에 따라 r-plane 사파이어 위에 성장되는 a-plane GaN 에피층의 결정성에 대하여 연구하였다. 또한 이번 연구의 결과를 선행 연구에서 single-step으로 r-plane 사파이어 위에 성장시킨 a-GaN 에피층의 결과와 비교하였다. Multi-step으로 r-plane 사파이어 위에 a-plane GaN 에피층을 성장시켰을 때, source HCl의 유량과 성장 시간이 증가함에 따라 a-plane GaN 에피층에 대한 rocking curve의 FWHM(Full Width at Half Maximum) 값이 감소하였다. 높은 source HCl의 유량을 갖는 first step과 second step의 성장 시간과 source HCl의 유량이 증가할수록 a-plane GaN 에피층 내부의 void가 감소하였다. 결과적으로 first step과 second step의 성장 시간이 가장 긴 조건에서 성장된 a-plane GaN 에피층이 가장 낮은 FWHM 값인 584 arcsec을 가지며, azimuth angle의 의존도가 가장 적은 것으로 확인되었다. In this study, the crystalline property of a-plane GaN epitaxial layer grown on r-plane sapphire by a HVPE method has been investigated according to the V/III ratio and the growth time of multi-step growth. Furthermore, these results were compared with the previous result obtained from the single-step growth of a-plane GaN on r-plane sapphire substrate. In the multi-step growth for a-plane GaN epitaxial layer on r-plane sapphire, the FWHM values of rocking curve in GaN epitaxial layer were decreased as the HCl source flow rate and the growth time were increased. The void formed in epitaxial layer was continuously decreased as the growth time in first step and second step using a higher HCl flow rate was increased. As a result, the GaN layer obtained with the longest growth time on the first step and second step exhibited the lowest FWHM values of 584 arcsec and the smallest dependence of azimuth angle.

원료물질에 따른 실리콘 질화막의 원자층 증착 특성 비교

이원준,이주현,이연승,나사균,박종욱,Lee Won-Jun,Lee Joo-Hyeon,Lee Yeon-Seong,Rha Sa-Kyun,Park Chong-Ook 한국재료학회 2004 한국재료학회지 Vol.14 No.2

Silicon nitride thin films were deposited by atomic layer deposition (ALD) technique in a batch-type reactor by alternating exposures of precursors. XJAKO200414714156408$_4$ or$ SiH_2$$Cl_2$ was used as the Si precursor, $NH_3$ was used as the N precursor, and the deposited films were characterized comparatively. The thickness of the film linearly increased with the number of deposition cycles, so that the thickness of the film can be precisely controlled by adjusting the number of cycles. As compared with the deposition using$ SiCl_4$, the deposition using $SiH_2$$Cl_2$ exhibited larger deposition rate at lower precursor exposures, and the deposited films using $SiH_2$$Cl_2$ had lower wet etch rate in a diluted HF solution. Silicon nitride films with the Si:N ratio of approximately 1:1 were obtained using either Si precursors at $500^{\circ}C$, however, the films deposited using $SiH_2$$Cl_2$ exhibited higher concentration of H as compared with those of the $SiC_4$ case. Silicon nitride thin films deposited by ALD showed similar physical properties, such as composition or integrity, with the silicon nitride films deposited by low-pressure chemical vapor deposition, lowering deposition temperature by more than $200^{\circ}C$.

HVPE법을 이용하여 PSS와 AlN Buffered PSS 위에 성장시킨 GaN 박막의 결정 특성

이원준,박미선,이원재,김일수,최영준,이혜용,Lee, Won Jun,Park, Mi Seon,Lee, Won Jae,Kim, Il Su,Choi, Young Jun,Lee, Hae Yong 한국전기전자재료학회 2018 전기전자재료학회논문지 Vol.31 No.6

An epitaxial GaN layer was grown on a cone-shape-patterned sapphire substrate (PSS) (Sample A) and an AlN-buffered PSS (Sample B) with two growth steps under the same process conditions by employing the hydride vapor phase epitaxy (HVPE) method. We have investigated the characteristics of the GaN layer grown on two kinds of substrates at each growth step. The cross-sectional SEM image of the GaN layer grown on the two types of substrates showed growth states of GaN layers formed during the 1st and 2nd growth steps with different growth durations. Dislocation density was obtained by calculation using the FWHM value of the rocking curve for (002) and (102). Sample A showed 2.62+08E and 6.66+08E and sample B exhibited 5.74+07E and 1.65+08E for two different planes. The red shift was observed is photoluminescence (PL) analysis and Raman spectroscopy results. GaN layers grown on AlN-buffered PSS exhibited better optical and crystallographic properties than GaN layers grown on PSS.

SiH₂Cl₂ 와 O₃을 이용한 원자층 증착법에 의해 제조된 실리콘 산화막의 특성

이원준,이주현,한창희,김운중,이연승,나사균,Lee Won-Jun,Lee Joo-Hyeon,Han Chang-Hee,Kim Un-Jung,Lee Youn-Seung,Rha Sa-Kyun 한국재료학회 2004 한국재료학회지 Vol.14 No.2

Silicon dioxide thin films were deposited on p-type Si (100) substrates by atomic layer deposition (ALD) method using alternating exposures of $SiH_2$$Cl_2$ and $O_3$ at $300^{\circ}C$. $O_3$ was generated by corona discharge inside the delivery line of $O_2$. The oxide film was deposited mainly from $O_3$ not from $O_2$, because the deposited film was not observed without corona discharge under the same process conditions. The growth rate of the deposited films increased linearly with increasing the exposures of $SiH_2$$Cl_2$ and $O_3$ simultaneously, and was saturated at approximately 0.35 nm/cycle with the reactant exposures over $3.6 ${\times}$ 10^{9}$ /L. At a fixed $SiH_2$$Cl_2$ exposure of $1.2 ${\times}$ 10^{9}$L, growth rate increased with $O_3$ exposure and was saturated at approximately 0.28 nm/cycle with $O_3$ exposures over$ 2.4 ${\times}$ 10^{9}$ L. The composition of the deposited film also varied with the exposure of $O_3$. The [O]/[Si] ratio gradually increased up to 2 with increasing the exposure of $O_3$. Finally, the characteristics of ALD films were compared with those of the silicon oxide films deposited by conventional chemical vapor deposition (CVD) methods. The silicon oxide film prepared by ALD at $300^{\circ}C$ showed better stoichiometry and wet etch rate than those of the silicon oxide films deposited by low-pressure CVD (LPCVD) and atmospheric-pressure CVD (APCVD) at the deposition temperatures ranging from 400 to $800^{\circ}C$.

Caffeic acid, chlorogenic acid, EGCG가 유방암 세포 T-47D의 p16 유전자 DNA methylation에 미치는 영향

이원준,Lee, Won-Jun 한국생명과학회 2007 생명과학회지 Vol.17 No.4

본 연구에서 사용한 coffee에 다량 함유된 caffeic acid와 chlorogenic acid, 녹차에 함유된 EGCG 성분은 암세포의 증식을 억제하는데 중요한 기능을 담당하는 세포주기 조절인자인 p16 유전자의 DNA methylation 패턴을 유방암 T-47D 세포에서 유의하게 변화시켰다. MSP를 이용하여 p16 유전자의 promoter 지역에서의 methylation상태의 변화를 살펴본 결과 caffeic acid, chlorogenic acid, EGCG는 유전자의 hypermethylation을 감소시켰으며, 이로 인해 demethylation된 p16 유전자가 증가하는 경향을 보였다. 이러한 연구 결과는 coffee 폴리페놀인 caffeic acid, chlorogenic acid와 녹차 폴리페놀인 EGCG는 세포내의 DNA methylation을 억제하는 기능을 가지는데, 이는 coffee폴리페놀과 같이 COMT 효소에 의한 methylation 부산물인 SAH의 증가에 의한 DNMT의 억제이거나, EGCG와 같이 DNMT와 직접적으로 결합하여 methylation 반응을 억제하는 mechanism에 의한 것으로 사료된다. 따라서 앞으로 이미 개발된 항암제뿐만 아니라, 부작용과 독성이 적은 식이성분에 대한 연구가 좀 더 심도 있게 이루어 져야 할 것이며, 이러한 연구들은 암이 발생되고 난 후 치료 요법으로 사용됨은 물론, 암이 발생하기 전에 사전 예방법으로도 널리 적용하는데 있어 중요한 이론적 토대를 마련할 것으로 사료된다. In the present investigation, we studied the modulating effects of caffeic acid, chlorogenic acid, and (-)-epigallocatechin-3-gallate(EGCG) on the methylation status of promoter regions of cell cycle regulator, p16, in human breast cancer T-47D cells. We demonstrated that treatment of T-47D cells with caffeic acid, chlorogenic acid, or EGCG partially inhibited the methylation status of the promoter regions of p16 genes determined by methylation-specific PCR. In contrast, unmethylated p16 genes were increased with the treatment of T-47D cells with $20{\mu}M$ of caffeic acid or chlorogenic acid for 6 days. Treatment of T-47D cells with 5, 20 or $50{\mu}M$ of EGCG increased the unmethylation status of p16 gene up to 100%, and the methylation-specific bands of this gene were decreased up to 50% in a concentration-dependent manner. The finding of present study demonstrated that coffee polyphenols and EGCG have strong inhibitory effects of the cellular DNA methylation process through increased formation of S-adenosyl-homocysteine(SAH) during the catechol-O-methyltransferase (COMT)- mediated O-methylation of these dietary chemicals or an direct inhibition of the DNA methyltransferases. In conclusion, various dietary polyphenols could reverse the methylation status of p16 gene in human breast T-47D cells.

적층 평판형 SOFC에서 LSM 전극의 기공 제어

이원준,여동훈,신효순,정대용,Lee, Won-Jun,Yeo, Dong-Hun,Shin, Hyo-Soon,Jeong, Dea-Yong 한국전기전자재료학회 2014 전기전자재료학회논문지 Vol.27 No.12

In solid oxide fuel cell system, yttria-stabilized zirconia is generally adopted as the electrolyte, which has high strength and superior oxygen ion conductivity, and the air electrode and the fuel electrode are attached to this. Recently, new structure of 'layered planar SOFC module' was suggested to solve the reliability problem due to the high temperature stability of a sealing agent and a binding material. In this study to materialize the air electrode in a layered planar SOFC module, the LSM ink was coated to form homogeneous electrode in the channel after the ink preparation. As the porosity control agent, PMMA or active carbon powder was adopted with use of a commercial dispersant in ethanol. The optimal amounts of both the porosity control agents and the dispersant were determined. Four (4) vol% of the dispersant for the LSM-PMMA case and 15 vol% for LSM-carbon powder showed the lowest viscosities respectively to indicate the best dispersed states of the slurries. With PMMA and carbon powder, sintered LSM ink shows the relatively homogeneous distributions of pores and with increases of the agents, the porosities increased in both cases. From this, it can be thought that the amount of the PMMA or carbon powder could be used to control the porosity of the LSM ink.

잉크젯 프린팅용 pink-red 수계 무기잉크의 제조 및 특성평가

이원준,황해진,한규성,조우석,김진호,Lee, Won-Jun,Hwang, Hae-Jin,Han, Kyu-Sung,Cho, Woo-Suk,Kim, Jin-Ho 한국결정성장학회 2015 韓國結晶成長學會誌 Vol.25 No.1

세라믹 잉크젯 기술은 아트타일, 장식용 도자기 등에 이용되고 있으며, 원료의 효율이 높고 낮은 제작비용으로 다양한 이미지를 빠르고 정확하게 인쇄할 수 있다는 장점을 가지고 있다. 잉크젯 프린팅 타일에 나노세라믹안료를 적용하기 위해서는 안정적인 잉크분산성 확보가 필수적이다. 본 논문에서는 잉크젯 인쇄용 수계 pink-red 세라믹잉크의 특성을 보여주고 있다. $CaCr_{0.1}Sn_{0.8}SiO_5$ 안료는 고상법을 이용하여 합성하였고, 잉크 토출 시 잉크젯 헤드의 노즐 막힘을 방지하기 위해 어트리션밀을 이용하여 분쇄한 안료를 사용 하였다. 수계 세라믹잉크 제조 시 $CaCr_{0.1}Sn_{0.8}SiO_5$ 나노안료의 농도는 10 wt%로 고정하였고, sodium dodecyl sulfate(SDS)를 0.4 wt% 첨가 하였을 때 최적의 분산성을 가지는 것을 확인할 수 있었다. 또한 수계 세라믹 잉크의 원활한 토출을 위해 polyvinyl alcohol(PVA)을 0.18 wt% 첨가하여 점도 조절을 하였다. 제조된 pinkred 세라믹 잉크는 토출 시 $180{\mu}s$ 이후 구형의 단일액적을 형성 하는 것을 확인할 수 있었다. Ceramic ink-jet printing technology in art tiles, decorated tablewares and other porcelain products has many advantages of fast and precision printing of various images with high efficiency and low cost. For the application to ink-jet printing, ceramic ink requires a stable dispersibility with nano-sized pigments. In this paper, characteristics of pink-red aqueous ceramic ink for ink-jet printing was demonstrated. $CaCr_{0.1}Sn_{0.8}SiO_5$ pigment was synthesized using solid state reaction and deagglomerated using attrition milling. The aqueous ceramic ink contains 10 wt% of the obtained $CaCr_{0.1}Sn_{0.8}SiO_5$ nanopigment with 0.4 wt% of sodium dodecyl sulfate (SDS) as a dispersion agent. Viscosity of $CaCr_{0.1}Sn_{0.8}SiO_5$ aqueous ceramic ink was adjusted using 0.18 wt% of polyvinyl alcohol (PVA) for a suitable jetting from the nozzle. The prepared pink-red ceramic ink showed a good jetting property with formation of a single sphere-shaped droplet after $180{\mu}s$ without a tail and satellite droplet.

서스펜션 플라즈마 용사를 이용한 이트리아 안정화 지르코니아 (7.5 wt% Y₂O₃-ZrO₂) 코팅 증착 및 특성

이원준,권창섭,김성원,오윤석,김형태,임대순,Lee, Won-Jun,Kwon, Chang-Sup,Kim, Seongwon,Oh, Yoon-Suk,Kim, Hyung-Tae,Lim, Dae-Soon 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.6

Yttria-stabilized zirconia (YSZ) coatings are fabricated via suspension plasma spray (SPS) for thermal barrier applications. Three different suspension sets are prepared by using a planetary mill as well as ball mill in order to examine the effect of starting suspension on the phase evolution and the microstructure of SPS prepared coatings. In the case of planetary-milled commercial YSZ powder, a deposited thick coating turns out to have a dense, vertically-cracked microstructure. In addition, a dense YSZ coating with fully developed phase can be obtained via suspension plasma spray with suspension from planetary-milled mixture of $Y_2O_3$ and $ZrO_2$.

디지털 컬러용 pink-red 고온발색 무기안료의 합성 및 특성평가

이원준,황해진,김진호,조우석,한규성,Lee, Won-Jun,Hwang, Hae-Jin,Kim, Jin-Ho,Cho, Woo-Suk,Han, Kyu-Sung 한국결정성장학회 2014 한국결정성장학회지 Vol.24 No.4

Digital ink-jet printing system has many advantages such as fast and fine printing of various images, high efficiency and low cost process. Generally digital ink-jet printing requires ceramic pigments of cyan, magenta, yellow and black with thermal and glaze stability above $1000^{\circ}C$ for the application of porcelain product design. In this study, pink-red colored $CaO-SnO_2-Cr_2O_3-SiO_2$ pigment was synthesized using solid state reaction. The synthesis conditions of $Ca(Cr,Sn)SiO_5$ pigment such as annealing temperature, amount of mineralizer and non-stoichiometric composition were optimized. Crystal structure and morphology of the obtained $Ca(Cr,Sn)SiO_5$ pigment were analyzed using XRD, SEM, PSA, FT-IR and effect of Cr substitution on the pigment color was analyzed using Uv-vis. spectrophotometer and CIE $L^*a^*b^*$ measurement. 최근 각광받고 있는 디지털 프린팅을 이용한 디자인 기법은 세밀한 표현과 다양한 이미지 구현이 가능하고, 원료의 낭비가 적어 효율성이 높은 장점을 가지고 있다. 디지털 프린팅 공정에서는 cyan, magenta, yellow, black이 기본적인 디지털 4원색으로 사용되며, 도자제품에 적용되는 세라믹 안료의 경우 $1000^{\circ}C$ 이상의 고온 소성이 가능하도록 우수한 열적, 유약 안정성과 발색 특성이 요구된다. 본 연구에서는 고상합성법을 이용하여 $CaO-SnO_2-Cr_2O_3-SiO_2$ 조성의 pink-red 고온발색 무기안료를 합성하였다. $Ca(Sn,Cr)SiO_5$ 세라믹 안료의 합성 조건에 따른 물성을 XRD, SEM, PSA, FT-IR를 이용하여 분석하였고, Cr 치환량 변화가 $Ca(Sn,Cr)SiO_5$ 무기 안료의 발색 거동에 미치는 영향을 Uv-vis.와 CIE 표색계 값($L^*a^*b^*$)을 기준으로 한 색도측정을 통해 관찰하였다.

금속불순물 제거를 위한 UV/ozone과 HF 세정연구

이원준,전형탁,Lee, Won-Jun,Jeon, Hyeong-Tak 한국재료학회 1996 한국재료학회지 Vol.6 No.11

반도체 소자가 고집적화 됨에 따라 단위공정의 수가 증가하게 되었고 동시에 실리콘 기판의 오염에 대한 문제가 증가하였다. 실리콘 기판의 주 오염물로는 유기물, 파티클, 금속분순물 등이 있으며 특히, Cu와 Fe과 같은 금속불순물은 이온주입 공정, reactive ion etching, photoresist ashing과 같은 실 공정 중에 1011-1013atoms/㎤정도로 오염이 되고 있다. 그러나 금속불순물 중 Cu와 같은 전기음성도가 실리콘 보다 큰 오염물질은 일반적인 습석세정방법으로는 제거하기 힘들다. 따라서 본 연구에서는 Cu와 Fe과 같은 금속불순물을 제거할 목적을 건식과 습식 세정방법을 혼합한 UV/ozone과 HF세정을 제안하여 실시하였다. CuCI2와 FeCI2 표준용액으로 실리콘 기판을 인위적 오염한 후 split 1(HF-only), split 2 (UV/ozone+HF), split 3 (UV/ozone + HF 2번 반복), split 4(UV/ozone-HF 3번 반복)를 실시하였고 TXRF(Total Reflection X-Ray Fluorescence)와 AFM(Atomic Force Microscope)으로 금속불순물 제거량과 표면거칠기를 각각 측정하였다. 또한 contact angle 측정으로 세정에 따른 표면상태도 측정하였다. TXRF 측정결과 split 4가 가장 적은 양의 금속불순물 잔류량을 보였으며 AFM 분석을 통한 표면거칠기도 가장 작은 RMS 값을 나타내었다. Contact angle 측정 결과 UV/ozone 처리는 친수성 표면을 형성하였고 HF처리는 소수성 표면을 형성하였다.