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Wet Chemical Etching of FeCrAl alloy for Microreactor Fabrication
라현욱,옥치원,한윤봉 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.1
Microreactors are finding increasing applications in the field of chemistry. In the past few years, microreactor chemistry has shown a great promise as a novel method on which to build new chemical technology and processes. To fabricate a microreactor, it is important to etch reactor materials such as glass, ceramic, and alloy for a pattern transfer. In this work, the wet chemical etching characteristics of FeCrAl alloy was investigated in terms of etch rate, surface morphology and etch profile by using various etching solutions. FeCrAl alloy was etched with H2SO4 and HCl solutions. When FeCrAl alloy was etched at a high concentration, the etch rate was faster than at a low concentration, but the etched surface of the former showed a rougher surface with etch residues. In the case of H2SO4 solution, the etched surface was relatively clean and smooth. The etch profile was a function of etching solution species and concentration.
P-842 : High Density Plasma Etching of Hard Mask Materials of SiO2, α-C:H, and ZnO
라현욱,옥치원,이석,김상훈,한윤봉 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.2
Due to the degradation of photoresists before the considerable depth and wide of etching of the substrate in the etch process, the photoresist cannot be used for a high aspect ratio etching process. Therefore, hard mask was widely used as an etch mask because of the high plasma resistant to achieve a considerable aspect ratio. This work contains the comparison of SiO2, α-C:H, and ZnO as hard mask materials for high density plasma etching of silicon in CF4/Ar discharges. The mask erosion and etch profile were affected by the processing parameters such as ICP source power, rf chuck power, operating pressure, and etch gas concentration. ZnO is the best, which fulfills the requirement of stable hard mask materials for CF4/Ar inductively coupled plasmas employed for silicon etching. While, α-C:H and SiO2 were eroded exposure to CF4/Ar inductively coupled plasmas.
라현욱,리즈완 칸,김진태,여찬혁,임연호,Ra, H.W.,Khan, R.,Kim, J.T.,Yeo, C.H.,Im, Y.H. 한국진공학회 2009 Applied Science and Convergence Technology Vol.18 No.4
본 연구에서는 열증착법을 이용하여 합성된 단결정의 산화아연 나노선들을 이용하여 전계효과트랜지스터를 제작하여 광학, 표면반응 및 전기화학적인 거동들에 대한 기초 연구들을 수행하였다. 100 nm의 지름과 길이 5 um 길이를 갖는 단결정 산화아연나노선의 전자 농도와 이동도는 각각 $1.30{\times}10^{18}cm^{-3}$과 $15.6cm^2V^{-1}s^{-1}$이었으며, 자외선을 나노선에 조사한 경우 약 400배 정도 전류가 증가하였다. 또한 나노선들은 여러 농도의 수소와 일산화탄소에 대해 잘 알려진 표면반응으로 기인한 기체 감지 특성을 보였고, 0.1 M NaCl 전해질 내에서 전형적인 산화아연의 나노선의 전기적 특성을 유지함을 확인하였다. We fabricated the field effect transistor using single crystalline ZnO nanowires synthesized by a conventional thermal evaporation method and investigated their basic properties under the various conditions such as ultraviolet irradiation, reducing gas and electrolyte. The typical carrier concentration and mobility of the single crystalline ZnO nanowire with a diameter of 100 nm and length of 5 um were $1.30{\times}10^{18}cm^{-3}$ and $15.6cm^2V^{-1}s^{-1}$, respectively. The current of ZnO nanowire under ultraviolet irradiation significantly increased about 400 times higher as compared to in the darkness. In addition, the ZnO nanowire showed typical sensing characteristics for $H_2$ and CO due to well-known surface reactions and typical current-voltage characteristics under the 0.1 M NaCl electrolyte.
P-499 : Heat Transfer Analysis of High Power LED packages
라현욱,옥치원,이석,김상훈,한윤봉 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.2
Light emitting diodes (LEDs) conventionally have been used for indicators. The introduction of high brightness LEDs with white light and monochromatic colors have led to a movement towards specialty and general illumination applications. The increased electrical currents used to drive the LEDs have focused more attention on the thermal managements of LED power packaging due to the efficiency and reliability of LEDs strictly depend on the junction temperature. In this work, we calculated the temperature distribution of LED power packaging as a function of input currents, used materials, and package geometry for a thermal design of high power LED. The temperature of high power LED package increased with the input current, particularly in glass silicon and epoxy resins. The temperature of high power LEDs package decreases with the thermal conductivity of thermal paste and heat slug size. The decrease in temperature is explained by increasing the heat flux through heat slug and heat conduction.
이석,김상훈,라현욱,한윤봉 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.2
ZnO films deposited on ZnO homo-buffer layer with different thicknesses were successfully prepared by atomic layer deposition. This two-step growth technique using homo-buffer layer is necessary to overcome the negative effects caused by hetero-buffer layer and lattice, thermal mismatch between ZnO and silicon. Crystallinity of ZnO films was characterized by X-ray diffractometer. FWHM of ZnO (002) peak is decreased with buffer layer thickness up to 327A. Surface morphology is also observed by scanning electron microscope (SEM). When the thickness of buffer layer is 327A, it shows mirror-like surface. The photoluminescence (PL) spectra show a strong UV emission at near 380nm. However, defect-related visible band also appears at all samples. The intensity ratio of the UV band to the visible band is largest at sample (c) with 327A buffer. The above results indicate that the optimum buffer layer thickness to improve the ZnO film quality is 327A.
E-23 : Structural and optical properties of flower and needle-shaped ZnO nanostructures by ALD
( Umar Ahmad ),이석,김상훈,라현욱,한윤봉 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.2
A novel method, atomic layer deposition is employed to grow the needle and flower-shaped ZnO arrays at different growth temperatures. The needle shaped nanostructures were grown on the Au catalyzed Si(100) substrate while the flower-shaped was grown without metal catalyst on Si(100) substrate. The high density needle-shaped ZnO nanostructures were confirmed using the field emission electron microscopy. Investigations using the high resolution transmission electron microscopy and selected area electron diffraction patterns confirmed that the as-grown nanostructures are single crystalline with wurtzite hexagonal structure and preferentially oriented in the c-axis direction. Optical properties of these structures were measured at room temperature by photoluminescence spectroscopy. The needle-shaped and flower shaped nanostructures show a broad band in the visible region with suppressed UV emission. It is indicating that these nanostructures have structural defects (oxygen vacancies and zinc interstitials etc).