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실리콘 및 사파이어 기판을 이용한 알루미늄의 양극산화 공정에 관한 연구
김문자,이진승,유지범,Kim Munja,Lee Jin-Seung,Yoo Ji-Beom 한국재료학회 2004 한국재료학회지 Vol.14 No.2
We carried out anodic aluminum oxide (AAO) on a Si and a sapphire substrate. For anodic oxidation of Al two types of specimens prepared were Al(0.5 $\mu\textrm{m}$)!Si and Al(0.5 $\mu\textrm{m}$)/Ti(0.1 $\mu\textrm{m}$)$SiO_2$(0.1 $\mu\textrm{m}$)/GaN(2 $\mu\textrm{m}$)/Sapphire. Surface morphology of Al film was analyzed depending on the deposition methods such as sputtering, thermal evaporation, and electron beam evaporation. Without conventional electron lithography, we obtained ordered nano-pattern of porous alumina by in- situ process. Electropolishing of Al layer was carried out to improve the surface morphology and evaluated. Two step anodizing was adopted for ordered regular array of AAO formation. The applied electric voltage was 40 V and oxalic acid was used as an electrolyte. The reference electrode was graphite. Through the optimization of process parameters such as electrolyte concentration, temperature, and process time, a regular array of AAO was formed on Si and sapphire substrate. In case of Si substrate the diameter of pore and distance between pores was 50 and 100 nm, respectively. In case of sapphire substrate, the diameter of pore and distance between pores was 40 and 80 nm, respectively
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솔 - 젤 법을 이용한 Pb(Zr, Ti)O₃ 박막의 성장 및 전기적 특성에 관한 연구
김봉주(Bong Ju Kim),전성진(Sungjin Jun),이재찬(Jaichan Lee),유지범(Ji Beom Yoo) 한국진공학회(ASCT) 1999 Applied Science and Convergence Technology Vol.8 No.4(1)
MEMS 소자 제작을 위하여 압전체로서 Pb(Zr,Ti)O₃ (以下 PZT)박막 및 전극물질로 전도성 산화물인(La,Sr)CoO₃ (以下 LSCO) 박막을 솜-젤 법으로 제작하였다. 실리카 후막과 PZT 박막의 접착성의 개선을 위해, 그리고 하부 전극으로 사용된 LSCO 박막은 물을 용매로 제작된 용액을 이용하여 제작되었으며 실리카와의 계면상태 향상을 위하여 고분자 계통의 첨가제인 poly vinyl alcohol(PVA)를 첨가하였다. PZT 박막에 사용된 용액은 보다 용이한 후막화를 위하여 높은 점성과 끓는점을 가지는 1,3-propanediol을 용매로 사용하였으며 출발물질의 합성에 있어서 반응성은 높지만 안정성이 약한 propoxide 계열의 특성을 보완하기 위하여 안정성이 높은 특성을 가지는 acetylacetone으로 부분치환을 시켜 제조하였다. 제조된 용액으로 스핀코팅 및 열처리를 통하여 박막을 성장시켰으며 약 0.8~1 ㎛ 두께의 균열이 없는 PZT 박막을 LSCO/SiO₂상에서 성장시킬 수 있었다. PZT 박막의 유전상수 및 유전손실 값은 각각 900~1200, 2~5%이었으며 Mach-Zehnder interferometer를 통해서 측정된 d₃₃ 압전상수는 100 kV/㎝의 전기장 하에서 200 pm/V이었다. Pb(Zr_(0.52)Ti_(0.48))O₃ (PZT) thick films as an actuating material with conducting oxides, (La_(0.5)Sr_(0.5)) CoO₃ (LSCO), have been fabricated by sol-gel method for Optical Micro-Electro-Mechanical System(MEMS) devices, in which PZT/LSCO/SiO₂ structures were used. In order to improve the adhesion between the silica and electrode, conducting oxides (LSCO) was used. Poly vinyl alcohol (PVA) was added to LSCO solution in order to enhance the wetting behavior of a water-based LSCO precursor solution and further to improve the adhesion between LSCO and SiO₂ layers. PZT films were made using 1-3 propanediol based precursor solution which has a high viscosity and a boiling point appropriate for thick film fabrication. In the precursor solution, Ti-propoxide and Zr-propoxide are partially substituted with acetylacetone to achieve the solution stability while maintaining reactivity. Crack free PZT films (0.8~1㎛) have been successfully fabricated at crystallization temperatures above 700℃. Dielectric constants and dielectric losses of the PZT films were 900~1200 and 2~5%, respectively. Piezoelectric properties of PZT films were measured by modified Mach Zehnder interferometer. Piezoelectric constant d₃₃ of the PZT films constrained by a substrate were 200 pm/V at 100 kV/㎝.
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성장정지효과에 의한 InGaAs / InP 양자우물구조의 Photoluminescence 특성 변화
문영부(Youngboo Moon),이태완(Tae-Wan Lee),김대연(Daeyeon Kim),윤의준(Euijoon Yoon),유지범(Ji-Beom Yoo) 한국진공학회(ASCT) 1998 Applied Science and Convergence Technology Vol.7 No.2
저압 MOCVD 방법을 이용하여 InGaAs/InP 양자우물구조를 성장하였다. 성장 정지 시간에 따른 photoluminescence 특성의 변화를 통하여 계면구조를 분석하였다. InP 표면을 PH₃ 분위기로, InGaAs 표면을 AsH₃분위기로 유지하며 성장을 정지하는 경우에는 성장 정지 시간이 길어짐에 따라 불순물 유입에 의한 것으로 생각되는 PL 반가폭의 증가를 관찰하였다. InP 표면에 AsH₃을 공급하는 경우에는 As-P 교환에 의해 우물층 두께가 증가하여 PL 피크가 저에너지로 이동하였고, 반가폭의 변화는 크지 않았다. 계면 양자우물구조를 형성하여 As-P 교환작용에 대해 조사하였고, 1-2 monolayer가 InAs 유효두께로 계산되었다. InGaAs 표면에 PH₃을 공급한 결과, PL 피크가 고에너지로 이동하는 것을 관찰하였고 동시에 반가폭도 증가하였다. 이는 메모리 효과에 의해 InP 층으로의 As 침투를 억제하고, InGaAs 표면에서의 국부적인 As-P 교환에 의한 것으로 생각된다. The InGaAs/InP quantum wells (QWs) were grown by low pressure metalorganic chemical vapor deposition and the effects of growth interruption steps on their interfacial structures were investigated by measuring photoluminescence spectra. When InP or InGaAs surface was treated under the same group V ambient, the full width at half maximum (FWHM) of the QW peak increased possibly due to the incorporation of impurities during the growth interruption time. When InP surface was treated under AsH₃, however, the PL peak showed red-shift due to the As-P exchange reaction and the change of FWHM was not remarkable. The effective thickness of InAs interfacial layer formed during AsH₃ treatment on the InP surface was calculated to be 1~2 monolayers. In the case of InGaAs treatment under PH₃ the PL peak energy and the FWHM increased. This results suggest that PH₃ treatment on the InGaAs surface suppresses the incorporation of As into the subsequent InP layer and the local replacement of As by P occurs simultaneously.
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초고속 광통신용 Avalanche photodiode의 제작 및 특성에 관한 연구
유지범,박찬용 成均館大學校 科學技術硏究所 1994 論文集 Vol.45 No.2
We review the characteristics of Avalache photodiode(APD) for long haul and high bit- rate optical fiber communication system including basic operating principle, excess noise factor, and bandwidth, and we also summarize recent progress. Separate absorption garding, charge and multiplication APD with charge plate layers instead of guard ring was designed and fabricated using metalorganic chemical vapor deposition and reactive ion etching technique. APD shows 37∼48V of breakdown voltage and very low dark current less than 10 nA at 90% of breakdown voltage. Receiver consisting of APD and Ga As pre - amplifier shows sensitivity of - 33.6dBm in the application of the pseudorandom 2^23-1 non- returen- to- zero(NRZ) patterns at 10^-9 bit error rate(BER).
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