UHV - LCVD 장치를 이용한 박막제작에 관한 연구 (Ⅰ) - 장치 제작을 중심으로 -

최원국(Won Kook Choi),윤덕주(Dug Ju Yun),공병인(Byung In Gong),김창현(Chang Hyun Kim),황정남(Chung Nam Whang),정광호(Kwang Ho Jeong) 한국진공학회(ASCT) 1993 Applied Science and Convergence Technology Vol.2 No.2

Si₃N₄와 SiO₂ 박막을 고순도로 생장시키기 위하여 UHV-LCVD 장치를 제작하였다. 이 장치는 CVD 반응실, 시료주입 장치, 가스주입 장치, 광여기를 위한 레이저 창, 질량분석 장치로 구성되어 있다. UHV-LCVD 는 low pressure, low vacuum CVD에 비해 제작상의 어려움이 따르나 초고진공 분위기에서 반응 가스의 양을 정확히 조절하여 고순도의 박막을 제작할 수 있었다. UHV-LCVD system was constructed for high quality silicon nitride thin film fabrication. This system consisted of a reaction chamber, an introduction chamber with sample load lock entry, a carbinet for gas manipulation controlling gas flow, a CO₂ laser and a Fourier transform mass spectrometer. Although the UHV-LCVD system construction was more sophisticated than low pressure CVD, highly pure thin films were fabricated by controlling gas mixing ratio and flow rate in ultra high vacuum surroundings.

라디칼 빔 보조 분자선 증착법 (Radical Beam Assisted Molecular Beam Epitaxy) 법에 의해 성장된 ZnO 박막의 발광 특성에 관한 연구

서효원,변동진,최원국,Suh, Hyo-Won,Byun, Dong-jin,Choi, Won-Kook 한국재료학회 2003 한국재료학회지 Vol.13 No.6

II-Ⅵ ZnO compound semiconductor thin films were grown on $\alpha$-Al$_2$O$_3$(0001) single crystal substrate by radical beam assisted molecular beam epitaxy and the optical properties were investigated. Zn(6N) was evaporated using Knudsen cell and O radical was assisted at the partial pressure of 1$\times$10$^{4}$ Torr and radical beam source of 250-450 W RF power. In $\theta$-2$\theta$ x-ray diffraction analysis, ZnO thin film with 500 nm thickness showed only ZnO(0002)and ZnO(0004) peaks is believed to be well grown along c-axis orientation. Photoluminescence (PL) measurement using He-Cd ($\lambda$=325 nm) laser is obtained in the temperature range of 9 K-300 K. At 9 K and 300 K, only near band edge (NBE) is observed and the FWHM's of PL peak of the ZnO deposited at 450 RF power are 45 meV and 145 meV respectively. From no observation of any weak deep level peak even at room temperature PL, the ZnO grains are regarded to contain very low defect density and impurity to cause the deep-level defects. The peak position of free exciton showed slightly red-shift as temperature was increased, and from this result the binding energy of free exciton can be experimentally determined as much as $58\pm$0.5 meV, which is very closed to that of ZnO bulk. By van der Pauw 4-point probe measurement, the grown ZnO is proved to be n-type with the electron concentration($n_{e}$ ) $1.69$\times$10^{18}$$cm^3$, mobility($\mu$) $-12.3\textrm{cm}^2$/Vㆍs, and resistivity($\rho$) 0.30 $\Omega$$\cdot$cm.

저에너지 고출력 이온빔을 이용한 polyvinylidene fluoride 표면의 초친수성화

박종용,정연식,최원국,Park Jong-Yong,Jung Yeon-Sik,Choi Won-Kook 한국재료학회 2005 한국재료학회지 Vol.15 No.6

Polyvinylidene fluoride (PVDF) surface was irradiated and became superhydrophilic by low energy (180 eV) and high flux $(\~10^{15}/cm{\cdot}s)$ ion beam. As an ion source, a closed electron Hall drift thruster of $\phi=70mm$ outer channel size without grid was adopted. Ar, $O_2$ and $N_2O$ were used for source gases. When $N_2O^+$ and $O_2^+$ reactive gas ion beam were irradiated with the ion fluence of $5\times10^{15}/cm^2$, the wetting angle for deionized water was drastically dropped from $61^{\circ}\;to\;4^{\circ}\;and\;2^{\circ}$, respectively. Surface energy was also increased up to from 44 mN/m to 81 mN/m. Change of chemical component in PVDF surface was analyzed by x-ray photoelectron spectroscopy. Such a great increase of the surface energy was intimately related with the increase of hydrophilic group component in reactive ion irradiated PVDF surfaces. By using an atomic force microscopy, the root-mean-square of surface roughness of ion irradiated PVDF was not much altered compared to that of pristine PVDF.

저 에너지 표면 개질 이온원이 설치된 진공 웹 공정을 이용한 2층 flexible copper clad laminate 제작

최형욱,박동희,최원국,Choi, Hyoung-Wook,Park, Dong-Hee,Choi, Won-Kook 한국재료학회 2007 한국재료학회지 Vol.17 No.10

In order to fabricate adhesiveless 2-layer flexible copper clad laminate (FCCL) used for COF (chip on film) with high peel strength, polyimide (PI; Kapton-EN, $38\;{\mu}m$) surface was modified by reactive $O_2^+$ and $N_2O^+$ ion beam irradiation. 300 mm-long linear electron-Hall drift ion source was used for ion irradiation with ion current density (J) higher than $0.5\;mA/cm^2$ and energy lower than 200 eV. By vacuum web coating process, PI surface was modified by linear ion source and then 10-20 nm thick Ni-Cr and 200 nm thick Cu film were in-situ sputtered as a tie layer and seed layer, respectively. Above this sputtered layer, another $8-9{\mu}m$ thick Cu layer was grown by electroplating and subsequently acid and base resistance and thermal stability were tested for examining the change of peel strength. Peel strength for the FCCLs treated by both $O_2^+$ and $N_2O^+$ ion irradiation showed similar magnitudes and increased as the thickness of tie layer increased. FCCL with Cu (200 nm)/Ni-Cr (20 nm)/PI structure irradiated with $N_2O^+$ at $1{\times}10^{16}/cm^2$ ion fluence was proved to have a strong peel strength of 0.73 kgf/cm for as-received and 0.34 kgf/cm after thermal test.

수소가 흡착된 W(011)표면의 재구성

김희봉(Kim Hei Bong),최원국(Choi Won Kook),홍사용(S. Y. Hong),황정남(Chung Nam Whang),정광호(Kwang Ho Jeong) 한국진공학회(ASCT) 1992 Applied Science and Convergence Technology Vol.1 No.1

최근 Angle Resolved Ultraviolet Photoemission Spectroscopy(ARUPS)를 통하여 Mo(011)과 W(011)의 surface Fermi contour에 관한 연구가 발표되었다. Hydrogen 흡착시 W(011)의 electron contour는 팽창하였다. 이것은 electron contour를 이루는 surface state가 hydrogen 흡착시 higher binding energy로 이동한 결과이다. Surface state의 higher binding energy로의 이동은 결국 band flattening으로 이해되며, 이 band flattening에 S. E. Trullinger의 long range dipole dipole force와 Kohn anomaly 현상을 부합시켜 W(011) surface에 수소 흡착시 일어나는 reconstruction 현상에 대한 설명을 시도해 보았다. Rencently, angle-resolved ultraviolet photoemission measurements of the Fermi surface contours for Mo(011) and W(011) are reported. The electron contour of W(011) is expanded upon hydrogen adsorption, which implies that the surface states consisting of electron pockets are shifted to higher binding energy. This phenomena can be explained by the band flattening. We explained here the reconstruction of W(011) surface induced by adsorption of hydrogen in terms of band flattening of surface states with a combination of S. E. Trullinger long range dipole-dipole interaction force and Kohn anomaly.

이온보조반응법으로 처리한 알루미나 코아의 인장결합강도에 관한 연구

김형섭,우이형,권긍록,최부병,최원국,Kim, Hyeong-Seob,Woo, Yi-Hyung,Kwon, Kung-Rock,Choi, Boo-Byung,Choi, Won-Kook 대한치과보철학회 2000 대한치과보철학회지 Vol.38 No.5

This study was undertaken to evaluate the tensile bond strength of In-Ceram alumina core treat-ed by ion assisted reaction(IAR). Ion assisted reaction is a prospective surface modification technique without damage by a keV low energy ion beam irradiation in reactive gas environments or reactive ion itself. 120 In-Ceram specimens were fabricated according to manufacturer's directions and divided into six groups by surface treatment methods of In-Ceram alumina core. SD group(control group): sandblasting SL group: sandblasting + silane treatment SC group: sandblasting + Siloc treatment IAR I group: sandblasting + Ion assisted reaction with argon ion and oxygen gas IAR II group: sandblasting + Ion assisted reaction with oxygen ion and oxygen gas IAR III group: sandblasting + Ion assisted reaction with oxygen ion only For measuring of tensile bond strength, pairs of specimens within a group were bonded with Panavia 21 resin cement using special device secured that the film thickness was $80{\mu}m$. The results of tensile strength were statistically analyzed with the SPSS release version 8.0 programs. Physical change like surface roughness of In-Ceram alumina core treated by ion assistad reaction was evaluated by Contact Angle Measurement, Scanning Electron Microscopy, Atomic Force Microscopy; chemical surface change was evaluated by X-ray Photoelectron Spectroscopy. The results as follows: 1. In tensile bond strength, there were no statistically significant differences with SC group, IAR groups and SL group except control group(P<0.05). 2. Contact angle measurement showed that wettability of In-Ceram alumina core was enhanced after IAR treatment. 3. SEM and AFM showed that surface roughness of In-Ceram alumina core was not changed after IAR treatment. 4. XPS showed that IAR treatment of In-Ceram alumina core was enabled to create a new functional layer. A keV IAR treatment of In-Ceram alumina core could enhanced tensile bond strength with resin cement. In the future, this ion assisted reaction may be used effectively in various dental materials as well as in In-Ceram to promote the bond strength to natural tooth structure.

RF 스퍼터링법으로 사파이어 기판 위에 성장한 ZnO와 ZnO : A1 박막의 질소 및 수소 후열처리에 따른 Photoluminescence 특성

조정,윤기현,정형진,최원국,Cho, Jung,Yoon, Ki-Hyun,Jung, Hyung-Jin,Choi, Won-Kook 한국재료학회 2001 한국재료학회지 Vol.11 No.10

2wt% $Al_2O_3-doped$ ZnO (AZO) thin films were deposited on sapphire (0001) single crystal substrate by parellel type rf magnetron sputtering at 55$0^{\circ}C$. The as-grown AZO thin films was polycrystalline and showed only broad deep defect-level photoluminescence (PL). In order to examine the change of PL property, AZO thin films were annealed in $N_2$ (N-AZO) and $H_2$ (H-AZO) at the temperature of $600^{\circ}C$~$1000^{\circ}C$ through rapid thermal annealing. After annealed at $800^{\circ}C$, N-AZO shows near band edge emission (NBE) with very small deep-level emission, and then N-AZO annealed at $900^{\circ}C$ shows only sharp NBE with 219 meV FWHM. In Comparison with N-AZO, H-AZO exhibits very interesting PL features. After $600^{\circ}C$ annealing, deep defect-level emission was quire quenched and NBE around 382 nm (3.2 eV) was observed, which can be explained by the $H_2$passivation effect. At elevated temperature, two interesting peaks corresponding to violet (406 nm, 3.05 eV) and blue (436 nm, 2.84 eV) emission was firstly observed in AZO thin films. Moreover, peculiar PL peak around 694 nm (1.78 eV) is also firstly observed in all the H-AZO thin films and this is believed good evidence of hydrogenation of AZO. Based on defect-level scheme calculated by using the full potential linear muffin-tin orbital (FP-LMTO), the emission 3.2 eV, 3.05 eV, 3.84 eV and 1.78 eV of H-AZO are substantially deginated as exciton emission, transition from conduction band maximum to $V_{ Zn},$ from $Zn_i$, to valence band maximum $(V_{BM})$ and from $V_{o} to V_BM}$, respectively.

진공 웹코터로 제작된 대면적 ITO/PET의 특성 연구

김지환,박동희,김종빈,변동진,최원국,Kim, Ji-Hwan,Park, Dong-Hee,Kim, Jong-Bin,Byun, Dong-Jin,Choi, Won-Kook 한국재료학회 2007 한국재료학회지 Vol.17 No.10

Indium tin oxide, which is used as transparent conducting layer in flexible device, is deposited on PET film by a magnetron sputtering in 300 mm wide roll-to-roll process (vacuum web coating). Sheet resistance, specific resistance and transmittance is differed by sputtering parameters such as working pressures, oxygen partial pressure, and thickness of ITO layer. ITO layer is deposited about 90 nm at roll speed of 0.24 m/min and its sputtering power is 3 kW. From the XRD spectrum deposited ITO layer is verified as amorphous. Under working pressure varied from $3{\times}10^{-4}\;Torr$ to $2{\times}10^{-3}\;Torr$, sheet resistance is lowest at the working pressure of $1{\times}10^{-3}\;Torr$ and its value is from $110\;{\Omega}/{\square}$ to $260\;{\Omega}/{\square}$ at the thickness of 90 nm. Oxygen partial pressure also varies sheet resistance and is optimized at the regime from 0.2% ($1.8{\times}10^{-6}\;Torr$) to 0.6% ($6{\times}10^{-6}\;Torr$). In this oxygen partial pressure sheet resistance is lower than $150\;{\Omega}/{\square}$. As ITO layer thickness increases, sheet resistance decreases down to $21\;{\Omega}/{\square}$ and specific resistance is about $7.5{\times}10.4{\Omega}cm$ in 340 nm thickness ITO layer. Transmittance is measured at the wavelength of 550 nm and is about 90% for 180 nm thickness ITO/PET.

고출력 저에너지 이온빔을 이용한 InP(100) 표면의 나노 패턴형성

박종용,최형욱,정연식,최원국,Park Jong Yong,Choi Hyoung Wook,Ermakov Y.,Jung Yeon Sik,Choi Won-Kook 한국재료학회 2005 한국재료학회지 Vol.15 No.6

InP(100) crystal surface was irradiated by ion beams with low energy $(180\~225\;eV)$ and high flux $(\~10^{15}/cm^2/s)$, Self-organization process induced by ion beam was investigated by examining nano structures formed during ion beam sputtering. As an ion source, an electrostatic closed electron Hall drift thruster with a broad beam size was used. While the incident angle $(\theta)$, ion flux (J), and ion fluence $(\phi)$ were changed and InP crystal was rotated, cone-like, ripple, and anistropic nanostrucuture formed on the surface were analyzed by an atomic force microscope. The wavelength of the ripple is about 40 nm smaller than ever reported values and depends on the ion flux as $\lambda{\propto}J^{-1/2}$, which is coincident with the B-H model. As the incident angle is varied, the root mean square of the surface roughness slightly increases up to the critical angle but suddenly decreases due to the decrease of sputtering yield. By the rotation of the sample, the formation of nano dots with the size of $95\~260\;nm$ is clearly observed.

이온빔 보조 증착법을 이용항 제작된 SnO$_2$에 초박막 Pd가 첨가된 박막형 가스센서의 메탄가스 감지특성

조정,조준식,윤기현,김현주,최원국,정형진,고석근,Cho, Jung,Cho, Jun-Sik,Yoon, Ki-Hyun,Kim, Hyun-Joo,Choi, Won-Kook,Jung, Hyung-Jin,Koh, Seok-Keun 한국세라믹학회 1998 한국세라믹학회지 Vol.35 No.8