• 한국표면공학회지
• /
• 제36권5호
• /
• pp.418-422
• /
• 2003

평판형 유도결합 플라즈마 식각장비(inductively coupled plasma etcher)를 이용하여 각종 공정조건들에 따른 GaAs의 식각특성을 연구하였다. 공정변수들은 ICP 소스파워(0-500 W), RIE 척파워(0-150 W), 가스 종류($BCl_3$, $BCl_3$/Ar, $BCl_3$/Ne) 및 가스혼합비였다. $BCl_3$ 가스만을 이용하여 GaAs를 식각한 경우보다 25%의 Ar이나 Ne같은 불활성 기체를 혼합한 $15BCl_3$/5Ar, $15BCl_3$/5Ne 가스를 이용한 경우의 식각률이 더 우수한 것을 확인하였다. 그리고 50% 이하의 Ar이 혼합된 $BCl_3$/Ar의 경우는 높은 식각률 (＞4,000 $\AA$/min)과 평탄한 표면(RMS roughness : ＜2 nm)을 얻을 수 있었지만 지나친 양(＞50%)의 Ar의 혼합은 오히려 표면을 거칠게 하거나 식각률을 떨어뜨리는 결과를 가져왔다. 그리고 20 sccm $BCl_3$, 100 W RIE 척파워, 300 W ICP 소스파워, 공정압력이 7.5 mTorr인 조건에서의 GaAs의 식각결과는 아주 우수한 특성(식각률: ∼ 4,000, $\AA$/min, 우수한 수직측벽도: ＞$87^{\circ}$, 평탄한 표면: RMS roughness : ∼0.6 nm)을 나타내었다.

• 대한기계학회논문집B
• /
• 제34권2호
• /
• pp.203-212
• /
• 2010

수분류 스프레이 냉각은 많은 산업적인 응용분야에 넓게 사용되고 있다. 본 연구는 수분류 스프레이가 표면거칠기가 주어진 $900^{\circ}C$ 고온강판의 표면에 충돌하는 경우, 열유속 및 열전달계수의 정량적인 측정을 통해 표면거칠기가 수분류 스프레이 냉각에 미치는 영향을 고찰하였다. 이 때의 국소 열유속은 시편, 카트리지히터, 열전대의 조합으로 고안된 고유의 열유속게이지를 제작하여 엄밀하게 측정되었다. 평균 표면거칠기 높이를 기준으로 40, 60, $80{\mu}M$의 3 가지 표면과 매끈한 표면에 대한 수분류 스프레이 냉각 의 열전달 현상이 비교 및 평가되었다. 표면거칠기가 주어진 표면에서의 돌출물은 얇은 열 경계층두께를 통과할 수 있기 때문에 표면거칠기가 주어진 경우에 열전달은 뚜렷하게 증가하였고, 표면거칠기의 의한 열전달 향상 기구는 서로 다른 비등영역에 대해 구분하여 조사되었다.

• 한국진공학회지
• /
• 제17권4호
• /
• pp.353-358
• /
• 2008

AlGaInP 기반 수직형 적색 LED (Light Emitting Diode)의 광추출효율을 증가시키기 위하여 화학적 etching 기술을 이용하여 n-AlGaInP 표면에 삼각꼴 모양의 거칠기를 형성하였다. Etching은 $H_3PO_4$계의 용액을 이용하여 화학적 etching을 진행 하였다. AlGaInP etching은 광추출효율의 증가와 밀접한 관련을 갖고 있으며 AFM (Atomic Force Microscope)을 이용하여 AlGaInP 표면을 분석하여 약 44 nm의 RMS (root-mean-square) 거칠기가 형성됨을 알 수 있었다. 광추출효율은 기존 수직형 적색 LED보다 거칠기가 형성된 수직형 적색 LED에서 41%의 높은 발광 효율을 보임으로써 고효율 수직형 적색 LED의 가능성을 보였다.

• Applied Science and Convergence Technology
• /
• 제25권2호
• /
• pp.32-35
• /
• 2016

Using conventional deposition techniques, we demonstrate a method to fabricate ultra-smooth 10 nm silver films without using a wetting layer or co-depositing another material. The argon working pressure plays a crucial role in achieving an excellent surface flatness for silver films deposited by DC magnetron sputtering on an InP substrate. The formation of ultra-smooth silver thin films is very sensitive to the argon pressure. At the optimum deposition condition, a uniform silver film with an rms surface roughness of 0.81 nm has been achieved.

• 한국진공학회지
• /
• 제8권3A호
• /
• pp.218-223
• /
• 1999

We investigated the interfacial reactions between the $Y_2O_3$ film deposited by ICB processing and p-type (100) Si substrates upon annealing treatments in $O_2$ and Ar gas ambients. we also investigated the evolution of surface morphology of ICB deposited $Y_2O_3$ films upon annealing treatments. We observed that the root-mean-square(RMS) value of surface roughness measured by AFM increased with annealing time at $800^{\circ}C$ in $O_2$ ambient, while the change of surface roughness was not observed in Ar ambient. We also found the growth of $SiO_2$ layer and the formation of yttium silicate layer. From the capacitance values $(C_{acc})$ measured by C-V measurements, the relative didldctric constant of $Y_2O_3$ film in metal-insulator-semiconductor(MIS) structure was estimated to be about 9.

• 대한금속재료학회지
• /
• 제46권4호
• /
• pp.217-222
• /
• 2008

Characteristics of etching and induced surface morphology variation by wet-etching of n-face n-type GaN were investigated using KOH solutions. It was observed that hexagonal pyramids were formed on the etched surface regardless of etching conditions. However, the size of the hexagonal pyramids was changed as the etching time and temperature increased, respectively. Initially, as the etching time and concentration of KOH solution increased, the hexagonal pyramid was observed to be dissociated into smaller pyramids. However, as the etching time increased further, the size of the hexagonal pyramids increased again, indicating that the etching of N-face n-type GaN by KOH solutions proceeded through the evolution of hexagonal pyramids, such as formation, dissociation and enlargement of pyramids. Furthermore, it was also observed that there is a correlation between the photoluminescence intensity of the etched surface and the value of root-mean-square roughness. The intensity of PL increased as the roughness value increased due to the enhancement of the extraction efficiency of the generated photons.

• 열처리공학회지
• /
• 제36권4호
• /
• pp.193-197
• /
• 2023

Transparent and conducting titanium (Ti) doped indium oxide (TIO) thin films were deposited on the poly-imide (PI) substrate with radio frequency magnetron sputtering and then electron irradiation was conducted on the TIO film's surface to investigate the effect electron irradiation on the crystallization and opto-electrical properties of the films. All x-ray diffraction (XRD) pattern showed two diffraction peaks of the In₂O₂ (431) and (444) planes with regardless of the electron beam irradiation energy. In the AFM analysis, the surface roughness of as deposited films was 3.29 nm, while the films electron irradiated at 700 eV, show a lower RMS roughness of 2.62 nm. In this study, the FOM of as deposited TIO films is 6.82 × 10^-3 Ω^-1, while the films electron irradiated at 500 eV show the higher FOM value of 1.0 × 10^-2 Ω^-1. Thus, it is concluded that the post-deposition electron beam irradiation at 500 eV is the one of effective methods of crystallization and enhancement of opto-electrical performance of TIO thin film deposited on the PI substrate.

• Structural Engineering and Mechanics
• /
• 제12권4호
• /
• pp.409-428
• /
• 2001

The characteristics of dynamic wheel loads of heavy vehicles running on bridge and rigid surface are investigated by using three-dimensional analytical model. The simulated dynamic wheel loads of vehicles are compared with the experimental results carried out by Road-Vehicles Research Institute of Netherlands Organization for Applied Scientific Research (TNO) to verify the validity of the analytical model. Also another comparison of the analytical result with the experimental one for Umeda Entrance Bridge of Hanshin Expressway in Osaka, Japan, is presented in this study. The agreement between the analytical and experimental results is satisfactory and encouraging the use of the analytical model in practice. Parametric study shows that the dynamic increment factor (DIF) of the bridge and RMS values of dynamic wheel loads are fluctuated according to vehicle speeds and vehicle types as well as roadway roughness conditions. Moreover, there exist strong dominant frequency resemblance between bounce motion of vehicle and bridge response as well as those relations between RMS values of dynamic wheel loads and dynamic increment factor (DIF) of bridges.

• 한국정밀공학회지
• /
• 제16권3호통권96호
• /
• pp.18-24
• /
• 1999

ThisPaper investigates the feasibility of using acoustic emission signal analysis for the detection of built-up edge during machining. Experiments were conducted on a CNC-lathe using conventional carbide insert tools under various cutting conditions. The cutting forces were also measured for comparisons. Experimental evidence is presented which indicates that the presence of a built-up edge can significantly affect the generation of acoustic emission in metal cutting. It is shown that under conditions in which a built-up edge is generated, the variation of $AE_{rms}$ signal with cutting speed can be quite different from the generally accepted linear, monotonic increase as previously reported. The feasibility of utilizing $AE_{rms}$ in built-up edge sensing is suggested.

• 한국전자파학회논문지
• /
• 제28권10호
• /
• pp.788-793
• /
• 2017

본 논문에서는 거친 바다표면의 마이크로파 반사를 계산할 수 있는 이론적 모델의 정확도를 검증한다. 우선 Pierson-Moskowitz 해양 스펙트럼을 이용하여 거친 바다표면을 생성하였다. 생성된 바다표면의 유의파고와 유효높이(root-mean square height)값을 추정하여 풍속에 따른 유의파고, 유효높이 관계식을 유도하였고, 다른 측정 데이터들과 비교하였다. 수치해석적 방법을 이용하여 다양한 거칠기 조건(풍속)에서 생성된 바다표면의 반사계수를 계산하였고, 기존에 반사계수를 계산하기 위해 사용하는 이론적 모델인 Ament 모델, PO(Physical Optics) 모델, GO(Geometrical Optics) 모델, B-M(Brown-Miller) 모델과 비교하였다. 비교적 거칠기가 매우 낮은 경우($kh_{rms}$<0.4, k는 파수, $h_{rms}$는 RMS 높이) 외에는 Ament 모델은 정확하지 않았다. 또한 거칠기가 크지 않은 바다($kh_{rms}$<10)에서는 PO, GO, B-M 모델들의 정확도가 보장되지만, 풍속이 높아 거칠기가 높은 바다($kh_{rms}$>10)에서는 입사각이 $70^{\circ}$ 이하에서는 PO 모델과 GO 모델이 수치해석결과와 비교적 잘 일치하였으며, $80^{\circ}$ 이상에서는 B-M 모델이 수치해석 결과와 비교적 잘 일치함을 보였다.