Visible Emission Properties of V2O5 Nanorods Prepared by Different Growth Methods

강만일,김석원,류지욱 한국진공학회 2014 Applied Science and Convergence Technology Vol.23 No.5

α-V2O5 nanorods were grown by means of electron beam irradiation and thermal oxidation methods and the visible emission properties of the nanorods grown by both methods were investigated. The growth and crystallinity of the nanorods were greatly enhanced by the insertion of a buffer layer. The emission spectra of the nanorods grown by thermal oxidation and electron beam irradiation showed a peak centered at 710∼720 nm, which is believed to be due to oxygen vacancies introduced during the growth process. Also, the emission peak centered at 530 nm observed in the V2O5 nanorods grown by electron beam irradiation was considered to be due to the band edge transition as a result of the enhanced crystallinity.

Dependence of the Optical Anisotropy of ZnO Thin Films on the Structural Properties

강만일,김용기,김석원,Ji-Wook Ryu 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.21

The structural properties and optical anisotropy of strained ZnO films prepared by rf magnetron sputtering were investigated. Anisotropic complex refractive index spectra of the films were determined by using the Adachi-New Forouhi dispersion model with phase-modulated spectroscopic ellipsometry in the range of 1.0 ∽ 4.0 eV. A negative strain was induced by the mismatch between the ZnO film and the Al2O3 substrate and decreased with improving crystallinity of the film. The size of the grains formed in the films showed a linear dependence on the strain. The optical anisotropy of the ZnO films was enhanced with improving crystallinity of the films. A shifting of the critical points of the anisotropic complex refractive index spectra was observed due to variations in the strain. The anisotropic complex refractive index spectra showed a strong dependence on structural changes in the ZnO films.

산소분압비에 따른 ZnO 박막의 성장특성

강만일,김문원,김용기,류지욱,장한오,Kang, Man-Il,Kim, Moon-Won,Kim, Yong-Gi,Ryu, Ji-Wook,Jang, Han-O 한국진공학회 2008 Applied Science and Convergence Technology Vol.17 No.3

산소분압비에 따른 ZnO 박막의 성장특성을 알아보기 위해 RF 스퍼터링 시스템을 이용하여 $0%{\sim}30%$의 산소분압비로 박막을 제작하였다. 위상변조방식의 분광타원계를 이용하여 $1.5{\sim}3.8eV$ 범위에 걸쳐 타원상수를 측정하였고, TL 분산관계식을 이용하여 최적맞춤한 결과 박막과 표면기칠기층의 두께, void 비율을 알 수 있었고, ZnO 알갱이의 크기는 산소분압비의 증가에 따라 그 크기가 작아짐을 알 수 있었다. 산소분압비에 따른 ZnO 박막의 밴드 갭은 산소유입량의 증가에 따라 증가하여 ZnO 박막의 광흡수 특성이 산소분압비에 크게 의존함을 알았고, 산소분압비의 증가는 결정의 불완전성을 증가시키는 것으로 나타났다. ZnO thin films were grown on a glass by RF sputtering system with RF power 100W and oxygen partial pressure of $0%{/sim}30%$. Elliptic constants were measured by using a phase modulated spectroscopic ellipsometer and analyzed with the Tauc-Lorentz dispersion formula and best fit method in the range of 1.5 to 3.8eV. Also, scanning electron microscope(SEM) was used for the analysis of surface crystallization condition. From elliptic constants spectra, optical constants, thickness and roughness of ZnO films were evaluated. Total thickness of ZnO films obtained by ellipsometry showed good agreement with SEM data. It was found that the grain size of the films were getting smaller with increasing oxygen partial pressure. Band-gap of ZnO films increase with the oxygen partial pressure. These findings clearly indicate that optical properties of ZnO films are strongly dependent on the oxygen partial pressure. It could be explained that increasing the oxygen partial pressure induced high crystalline imperfection in the ZnO films.

SiO₂/TiO₂/ZrO₂ 광대역 반사방지막의 제작 및 광학적 특성 분석

강만일,류지욱,김기원,김찬희,백영기,이동현,이성룡,Kang, M.I.,Ryu, J.W.,Kim, K.W.,Kim, C.H.,Baek, Y.K.,Lee, D.H.,Lee, S.R. 한국진공학회 2008 Applied Science and Convergence Technology Vol.17 No.2

$SiO_2/TiO_2/ZrO_2$ broadband anti-reflective multi-layer thin films were prepared at room temperature by RF sputtering system. Optical constants and structural properties on each layer of films were analyzed by spectroscopic ellipsometer and transmittance spectra of the films were measured by $UV-V_{is}$ spectrophotometer in the range of 300$\sim$900 nm. To evaluate the films, we compared the measured and analyzed spectra with designed spectra. We investigated influence of discrepancy of thickness and refractive indices of each layer on changes of the transmittance spectra. It was found that refractive indices and shape of dispersion of deposition materials are more contributed to changes of the transmittance spectra than thickness of layer. RF 스퍼터링 시스템을 이용하여 $SiO_2/TiO_2/ZrO_2$ 광대역 반사방지막을 단계별로 제작하였고, 분광타원계와 $UV-V_{is}$ 분광광도계를 이용하여 박막의 두께, 굴절률 및 투과율 스펙트럼을 300$\sim$900nm의 파장 영역에 걸쳐 측정 및 분석하였다. 측정 및 분석된 박막의 두께, 굴절률 및 투과율 스펙트럼을 설계값과 비교 평가한 결과 각층의 두께, 굴절률의 차이에 따른 투과율의 변화를 분석할 수 있었고, 박막의 두께보다는 굴절률과 굴절률의 분산형태가 투과율의 변화에 더 크게 기여함을 알 수 있었다.

자치시대 지방탐구 ( 3 ) / 남제주군 : 남제주군이 펼치는 「 3 . 3 신풍운동 」 - 공직자가 솔선하여 주민의식 개혁으로 파급시킨다

강만일 대한지방행정공제회 1997 地方行政 Vol.46 No.519

분광타원법을 이용한 다공질규소의 유전율 측정에 관한 연구

강만일,류지욱 公州大學校 基礎科學硏究所 2003 自然科學硏究 Vol.10 No.-

다공질규소의 유전율을 측정하기 위해 위상변조방식의 분광타원법을 이용하였다. 분석용 프로그램을 이용한 분석을 통해 다공질규소층의 두께와 그것을 구성하는 Si와 void의 비율을 알 수 있었고, 전류밀도가 증가함에 따라 층의 두께가 선형적으로 증가하는 것을 알았다. 또한 EMA 근사식의 적용결과 다공질규소의 흡수 스펙트럼은 단결정규소의 스펙트럼과 아주 유사하게 나타남을 확인하였고, 다공질규소의 복소유전율이 void의 비율이 증가함에 따라 감소한다는 것을 알 수 있었다. To determine permittivity of porous silicon that is made of anodezed crystalline silicon, we measured the elliptic constants in the range of 300~800nm wavelengths using the phase modulated spectroscopic ellipsometer. We obtained complex permittivity of porous silicon through analysis of elliptic constants measured by the ellipsometer. It is found that the complex permittivity becomes smaller as the void volume gets larger in the porous silicon layer and the thickness of porous silicon layer is proportional to current density.

Optical characteristics of amorphous V2O5 thin films colored by an excimer laser

강만일,오은지,김인구,김석원,류지욱,김용기 한국물리학회 2012 Current Applied Physics Vol.12 No.2

The V2O5 films were prepared by an RF sputtering method, and the amorphous films were colored by an UV excimer laser. The crystallinity of the as-grown V2O5 film was degenerated greatly by laser irradiation,as determined by X-ray diffraction (XRD) and Raman studies. The transmission and complex refractive index spectra of the V2O5 film were affected by variations in the microstructure, including the surface morphology, crystalline structure, and substoichiometry with an oxygen deficiency. Considerable emissions due to oxygen vacancies and band transition of photoluminescence (PL) peaks were observed,and the peaks were significantly changed after laser irradiation. The variations in the optical properties in both films may be attributed to oxygen deficiency induced by laser irradiation.

비정질과 결정질 V₂O₅ 박막의 온도에 따른 발광특성

강만일,추민우,김석원,Kang, Manil,Chu, Minwoo,Kim, Sok Won 한국결정성장학회 2014 한국결정성장학회지 Vol.24 No.5

$V_2O_5$ 박막에서의 PL 특성을 조사하기 위해 RF 스퍼터링법을 이용하여 비정질과 결정질 $V_2O_5$ 박막을 제작하였고, 10~300 K의 온도까지 PL 스펙트럼을 측정하였다. 상온에서 성장된 비정질 박막에서는 ~505 nm를 중심으로 하는 하나의 PL 피크만이 관찰되었고, 결정질 $V_2O_5$ 박막에서는 505 nm를 중심으로 하는 피크와 산소결함에 의한 것으로 알려진 ~695 nm를 중심으로 하는 피크가 관찰되었다. 비정질과 결정질 $V_2O_5$ 박막에서 관찰되는 505 nm에서의 PL 피크의 위치는 온도에 강한 의존성을 보였고, 그 값은 300 K에서 2.45 eV였고, 10 K에서 2.35 eV였다. 505 nm에서의 PL은 $V_2O_5$에서의 밴드 에너지 전이에 의한 것이었으며, 또한 온도의 감소에 따른 피크 위치 에너지의 감소는 전자-포논 상호작용의 감소에 의한 격자팽창효과의 감소 때문이었다. In order to investigate the photoluminescence (PL) properties of $V_2O_5$ films, amorphous and crystalline films were prepared by using RF sputtering system, and the PL spectra of the films were measured at the temperatures ranging from 300 K to 10 K. In the amorphous $V_2O_5$ film grown at room temperature, a PL peak centered at ~505 nm was only observed, and in the crystalline $V_2O_5$ film, two peaks centered at ~505 nm and ~695 nm, which is known to correspond to oxygen defects, were revealed. The position of PL peak centered at 505 nm for both the amorphous and crystalline $V_2O_5$ films showed a strong dependence on temperature, and the positions were 2.45 eV at 300 K and 2.35 eV at 10 K, respectively. The PL at 505 nm was due to the band energy transition in $V_2O_5$, and also, the reduction of the peak position energy with decreasing temperature was caused by a decrement of the lattice dilatation effect with reducing electron-phonon interaction.

Optical Properties of Sputtered Indium-tin-oxide Thin Films

강만일,김인구,추민우,김석원,류지욱 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.51

Indium-tin-oxide (ITO) thin films, used as transparent conductive electrodes in various optoelectronics fields, were prepared via RF sputtering at different substrate temperatures. The effects of substrate temperature on the optical properties were investigated. The structures and the optical constants of the films were successfully analyzed using the classical formula. The microstructures and the resistances of ITO films were strongly influenced by the substrate temperature, and the optical properties of the films significantly changed with variations in the microstructure and the resistance induced by increasing the substrate temperature. The reduction of the resistance, indicating an increase in the free electron concentration, induced a Burstein-Moss shift in the UV region and a Drude absorption in the near infrared (NIR) region.

자동차 전면유리용 ITO 박막의 발열특성

강만일,김인혁,황보현,김석원 한국물리학회 2016 새물리 Vol.66 No.11

ITO 박막을 자동차의 전면유리에서의 발열용 필름으로 활용하기 위해 롤투롤 (roll-to-roll) 스퍼터링법을 이용하여 PET 기판위에 ITO 박막을 제작하였고, 제작된 박막에 직류 전류를 인가하여 박막에서의 발열특성을 조사하였으며, 열화상카메라를 이용하여 발열분포를 조사하였다. 모든 ITO 박막에서의 발열은 측정시간에 대한 지수함수의 역수($1-e^{-t}$) 형태의 온도상승곡선을 보였으며, 5분 내에 온도 상승이 완료되었다. 측정시간이 300초 이고, 인가전압이 50 V일 때, 30$\times$30 cm에서는 55 $^\circ$C, 50$\times$50 cm에서는 12 $^\circ$C, 70$\times$70 cm에서는 7.8 $^\circ$C의 온도상승을 보였다. 면적에 따른 박막에서의 발열온도는 파워함수의 역수 ($y=ax^{-b}$) 형태의 감소곡선을 보였고, 전류밀도는 면적이 증가함에 따라 선형적으로 감소하였다. 이러한 전류밀도의 큰 감소에 의해 ITO 박막의 온도가 낮아졌다. In order to apply Indium-tin-oxide (ITO) thin films as exothermic films in front windows of automobiles, we prepared ITO films on polyethylene terephthalate (PET) substrates by using a roll-to-roll sputtering technique, investigated the exothermic properties by applying a DC current, and observed the temperature distribution by using a thermal imaging camera. The temperature of the ITO thin film increased according to the exponential function ($1-e^{-t}$), and reached an asymptotic value within 5 minutes. The ITO films with sizes of 30$\times$30, 50$\times$50, and 70$\times$70 cm$^2$ showed temperatures of 55, 12, and 7.8 $^\circ$C, respectively, at a measuring time of 300 s and at an applied voltage of 50 V. The exothermic temperature ($y$) in the ITO film decreased with increasing area ($x$) as a power function ($y=ax^{-b}$), and the current density in the films linearly decreased with increasing film area. The reduction of the temperature in the ITO film was due to the large drop in the current density.