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Microstructure of Intrinsic ZnO Thin Film Grown by Using Atomic Layer Deposition
변동진,허재성,Samseok Jang,김동환,손창식 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
ZnO thin lms were deposited by using atomic layer deposition with a fixed purging time of the DEZinc and the H2O sources of 8 sec and an injection time of 1 sec per source. The ZnO films were formed in the temperature range from 30 ℃ to 300 ℃. The microstructure was altered by varying the temperature, and the shapes and the sizes of the grains were altered by changing the preferred orientation. The surface morphologies and the shapes of the grains were correlated with the preferred orientation, which changed with the growth temperature.
질화처리에 의한 기판 평면 평활도의 변화가 GaN 성장에 미치는 영향
정재식,변동진,김병화,이재인,유지범,금동화,Jeong, Jae-Sik,Byeon, Dong-Jin,Kim, Byeong-Hwa,Lee, Jae-In,Yu, Ji-Beom,Geum, Dong-Hwa 한국재료학회 1997 한국재료학회지 Vol.7 No.11
LED와 LD의 수명과 효율은 결정에 존재하는 결함의 밀도에 반비례하며, 이러한 결함의 밀도는 적당한 기판을 사용하거나, 기판의 표면을 적절하게 제어함으로써 줄일 수 있다. GaN성장시 원자 단위의 매끄러운 표면은 완충충 성장이나 질화처리를 함으로써 얻어질 수 있다. 이렇게 얻어진 원자 단위의 매끄러운 표면에 의해 기판과 박막상이의 계면 자유에너지가 감소하기 때문에 2D성장이 촉진된다. 사파이어(AI$_{2}$O$_{3}$(0001))기판을 사용한 GaN 왕충충성장과 진화처리에 대한 최적조건은 AFM(Atomic Force Microscope)측정 결과에 의해 결정되었다. AFM에 의해 얻어진 표면 평활도의 개념은 사파이어 기판을 사용한 GaN박막성장의 최적조건을 결정하는 데 있어서 높은 신뢰도를 가질 수 있다.
활성화 이온빔 처리된 사파이어 기판상 MOCVD로 성장시킨 GaN의 열처리 효과
이상진,변동진,홍창희,김긍호,Lee, Sang-Jin,Byeon, Dong-Jin,Hong, Chang-Hui,Kim, Geung-Ho 한국재료학회 2001 한국재료학회지 Vol.11 No.3
사파이어 (0001) 기판의 활성화 이온빔 (RIB) 처리 후 MOCVD에서 성장한 GaN박막의 열처리를 통한 구조 변화를 살펴보고, 전기적 성질의 변화를 관찰하기 위하여 전기로를 이용하여 열처리를 하였다. 시편의 분석을 위하여 DCXRD, Hall, TEM을 사용하였다. 100$0^{\circ}C$에서 시간을 변화시키면서 열처리한 시편에서 DCXRD의 FWHM는 약 50 arc-sec 정도 감소하였고, Hall 이동도는 약 80$\textrm{cm}^2$/V.sec 정도 향상되었다. 가장 좋은 Hall 이동도를 보인 처리된 시편과 처리 전 시편의 TEM 비교 관찰에서 전위 밀도는 56~69% 정도 감소하였고 격자의 변형도 줄어들었다. 이것은 결정의 질과 전기적 성질 사이의 상관관계를 암시하며, 기판의 RIB 처리와 성장 후 적절한 열처리의 조합이 MOCVD로 성장시킨 GaN 박막의 특성을 개선시키는 것을 명확하게 보여준다. GaN is a key material for blue and ultraviolet optoelectronics. Postannealing process was employed to investigate the structural change and the effect on electrical property of the GaN thin film grown on reactive ion beam(RIB) treated sapphire (0001) substrate. Full width half maximum (FWHM) of double crystal x-ray diffraction (DCXRD) spectra and Hall mobility of the specimen were significantly changed depending on the postannealing time at $1000^{\circ}C$ in N2 atmosphere. FWHM of DCXRD reduced upto about 50arc-sec and the mobility increased about $80\textrm{cm}^2$/V.sec. The postannealed specimen with the best mobility was compared with sample without annealing by TEM. The former sample showed a decrease in the lattice strain and reduction of dislocation density by about 56~59%. This implies that there is a strong correlation between crystalline quality and the electrical property of the film. The Present results clearly show that the combination of RIB pretreatment and proper post annealing conditions results in the improved properties of GaN films grown by MOCVD.
손재천,변동진 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.2
A non-integrated type noise filter on a coplanar waveguide (CPW) transmission line is demonstrated by using a highly resistive Co41Fe38Al13O8 nanogranular thin film with the dimensions of 4 mm (l) 4 mm (w) 0.1 m (t). The noise suppression characteristics are evaluated without placing an insulating layer between the CPW line and the magnetic thin film. The insertion loss is very low being less than 0.3 dB and this low value is maintained up to 2 GHz. At a ferromagnetic resonance frequency of 3.3 GHz, the power loss is very large and the degree of noise attenuation is measured to be 3 dB. This level of noise attenuation is still small for real applications; however, considering the small magnetic volume used in this work, further improvement is expected by simply increasing the magnetic volume and by integrating the magnetic thin film into the CPW transmission line.
Nano-granular Co-Fe-Al-O Soft Ferromagnetic Thin Films for RF Electromagnetic-noise Filters
손재천,변동진 한국전기전자재료학회 2006 Transactions on Electrical and Electronic Material Vol.7 No.1
Co-Fe-Al-O nano-granular thin films with high electrical resistivity, fabricated by radio frequency magnetron sputtering under an Ar+O2 atmosphere, are found to show good soft magnetic properties in the GHz frequency range. The real part value of the relative permeability is 260 at low frequencies and this value is maintained up to the GHz frequency range. A non-integrated type noise filter on a coplanar waveguide transmission line is demonstrated by using the Co-Fe-Al-O nano-granular thin film with the dimensions of 4 mm (l) × 4 mm (w) × 0.1 mm (t). The insertion loss is very low being less than 0.3 dB and this low value is maintained up to 2 GHz. At a ferromagnetic resonance frequency of 3.3 GHz, the degree of noise suppression is measured to be 3 dB. This level of noise attenuation is small for real applications, but there is much room for further improvement by increasing the magnetic volume and integrating the magnetic thin film into the CPW transmission line.
Spin-coating법에 의한 $TiO_2$의 광촉매 효율
김범준,변동진,이중기,박달근,Kim, Beom-Jun,Byeon, Dong-Jin,Lee, Jung-Gi,Park, Dal-Geun 한국재료학회 2000 한국재료학회지 Vol.10 No.4
TiO$_2$thin films were prepared on the glass by a conventional spin coating method with $TiO_2$ sol(30wt%, anatase). The thickness of the thin films were controlled by the number of coating cycles: one cycle is composed of spin coating, drying, and heating process. The reaction rate of the film was obtained by the photodecomposition of gaseous benzene under 0.44 and 2.0mW/$\textrm{cm}^2$ UV light on the film surface. For an incident UV light intensity of 0.44mW/$\textrm{cm}^2$, the reaction rate was increased with the thickness of the film, caused by extent of surface area, but there was no change over the thickness of about 4$\mu\textrm{m}$. The porous $TiO_2$ thin film has comparatively vast effective surface area, which under relatively high-intensity UV illumination causes the reaction rate to be controlled by the film thickness. $TiO_2$sol(30wt%, anatase)을 이용하여 스핀코팅으로 유리기판에 $TiO_2$박막을 제조하였다. 박막의 두께는 코팅주기의 횟수가 조절하였다. 한 코팅주기는 스핀코팅, 건조, 열처리를 포함한다. 박막의 반응성은 막 위에서의 자외선강도가 0.44와 2.mW/$\textrm{cm}^2$인 조건에서 벤젠기체의 광분해 속도를 통해 조사하였다. 박막의 두께가 증가할수록 표면적으로 증가로 인해 반응성은 증가하였으며, 0.44mW/$\textrm{cm}^2$일 때 4$\mu\textrm{m}$정도 이상의 두께에서 반응성은 더 이상 증가되지 않았다. porous한 $TiO_2$박막은 비교적 넓은 유효표면적을 가지고 있으며, 그것은 비교적 높은 자외선 강도하에서 박막두께에 따라 반응속도를 증가시키는 결과를 낳았다.