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RF-마그네트론 스퍼터링법으로 제작한 이층형 PZT의 특성평가
임실묵(Sil-Mook Lim) 한국산학기술학회 2020 한국산학기술학회논문지 Vol.21 No.8
페로부스카이트(Perovskite) 구조의 Pb(Zr,Ti)O₃(PZT)는 우수한 강유전 특성으로 인해 유전체, 압전체, 초전체재료로 널리 사용된다. Pb1.3(Zr0.52Ti0.48)O₃ 조성의 스퍼터링 타겟을 제조하여 RF 마그네트론 스퍼터링 공정으로 PZT박막을 형성하였다. PZT박막은 동일 스퍼터링 출력으로 연속 제조한 단층형 PZT와 2단계화한 스퍼터링 출력으로 제조한 2층형 PZT박막으로 구분하여 제조하였다. 2층형의 PZT는 저출력의 스퍼터링 조건으로 제작한 하부층과, 단층형 PZT와 동일한 조건으로 제작한 상부층으로 이루어진다. 제조한 박막에 대한 엑스선 회절분석결과, 단층형 PZT에서는 페로부스카이트상(Perovskite Phase)과 미소한 파이로클로르상(Pyrochlore Phase)이 혼합된 상태로 존재하나, 2층형 PZT에서는 페로부스카이트상만이 검출되었다. 전자현미경과 원자힘 현미경으로 표면상태를 관찰한 결과, 2층형 PZT박막의 상부는 단층형에 비해 치밀하고 평활한 표면상태를 나타냈으며, 단층형에 비해 낮은 표면거칠기값(RMS)을 보였다. 또한 이층형 PZT는 단층형에 비해 우수한 대칭성의 분극곡선형태를 보였고, 단층형에 비해 매우 저감된 1×10<SUP>-5</SUP> A/㎝² 이하수준의 누설전류 특성을 나타냈다. 이층형 PZT에서 보이는 이러한 현상은 치밀하게 형성한 하부 PZT층이 순차적으로 형성되는 상부PZT내의 미소 파이로클로르상 형성을 억제하여, 순수한 페로부스카이트상으로의 성장을 유도한 것으로 판단된다. Pb(Zr,Ti)O₃(denoted as PZT) in the perovskite phase is used as a dielectric, piezoelectric, and super appetizer material owing to its ferroelectric properties. A PZT film was formed by an RF magnetron sputtering process by preparing a target composed of Pb1.3(Zr0.52Ti0.48)O₃. The PZT film was formed by dividing the material into a mono-layer PZT produced continuously with the same sputtering power and a bi-layer PZT produced with two-stage sputtering power. The bi-layer PZT consisted of a lower layer produced under low-power sputtering conditions and an upper layer produced under the same conditions as the mono-layer PZT. XRD revealed small amounts of pyrochlore phase in the mono-layer PZT, but only the perovskite phase was detected in the bi-layer PZT. SEM and AFM revealed the upper part of the bi-layer PZT to be more compact and smooth. Moreover, the bi-layered PZT showed superior symmetry polarization and a significantly reduced leakage current of less than 1×10<SUP>-5</SUP> A/cm². This phenomenon observed in bi-layer PZT was attributed to the induction of growth into a pure perovskite phase by suppressing the formation of a pyrochlore phase in the upper PZT layer where the densely formed lower PZT layer was produced sequentially.
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Metal PCB에 있어서 양극산화법으로 제작한 Al₂O₃ 절연막의 방열특성
조재승(Jae-Seung Jo),김정호(Jeong-Ho Kim),고상원(Sang-Won Ko),임실묵(Sil-Mook Lim) 한국표면공학회 2015 한국표면공학회지 Vol.48 No.2
High efficiency LED device is being concerned due to its high heat loss, and such heat loss will cause a shorter lifespan and lower efficiency. Since there is a demand for the materials that can release heat quickly into the external air, the organic insulating layer was required to be replaced with high thermal conductive materials such as metal or ceramics. Through anodizing the upper layer of Al, the Breakdown Voltage of 3kV was obtained by using an uniform thickness of 60 μm aluminum oxide(Al₂O₃) and was carried out to determine the optimum process conditions when thermal cracking does not occur. Two Ni layers were formed above the layer of Al₂O₃ by sputtering deposition and electroplating process, and saccharin was added for the purpose of minimizing the remain stress in electroplating process. The results presented that the 3-layer film including the Ni layer has an adhesive force of 10N and the thermal conductivity for heat dissipation is achieved by 150W/mK level, and leads to improvement about 7 times or above in thermal conductivity, as opposed to the organic insulation layer.
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1-3형 압전 복합체를 이용한 광대역 수중 통신용 음향 트랜스듀서에 관한 연구
이경우(KYUNG-WOO LEE),소형종(HYOUNG-JONG SO),임실묵(SIL-MOOK LIM),김원호(WON-HO KIM),조운현(UN-HYUN CHO) 한국해양공학회 2008 韓國海洋工學會誌 Vol.22 No.2
Recently, many researches in relation to data transmission with faster speed and greater volume, many researches have been carried out on sonnr systems for underwater communimtion. According to these researches, an acoustic transducer for underwater communication requires wide bandwidth properties. In domestic researches for underwater communimtion sonar, an operating frequency in the range of 20-40 ㎑ is used. In this paper, we propose anon-resonance type acoustic transducer for underwater communimtion. The TVR (transmitting voltage response) characteristics increased linearly as the frequency increased, and the RVS (receiving voltage sensitivity) characteristics were constant as the frequency increased. Traditional techniques for wide bandwidth transducershave a limit and a transmission loss difference at lower and higher frequency operating ranges. In this paper, the new transducer proposed decreased the transmission loss under some conditions. It was optimized with the FE analysis tool (ATILA) and evaluated using the TVR and the RVS characteristics in the range of 10-90 ㎑. The value of TVR was 138 ㏈ at 20 ㎑ and 148 ㏈ at 40 ㎑, and the differences was 12 ㏈. The value of RVS was 195±2 ㏈ and nearly constant. From theseresults, it is certain that the developed transducers mn be used for an underwater communimtion network in the 1.3 ㎞ range with both a 20 ㎑ bandwidth and 30 ㎑ center frequency.
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1-3형 압전복합체를 이용한 광대역 수중 음향 트랜스듀서 개발
이경우(Lee, Kyung-Woo),소형종(So, Hyoung-Jong),임실묵(Lim, Sil-Mook),김원호(Kim, Won-Ho),김대연(Kim, Dae-Yun) 한국소음진동공학회 2008 한국소음진동공학회 논문집 Vol.18 No.4
Recently, it is required that acoustic transducers for underwater detection and communication sensor have wide bandwidth and low operating frequency. In this research, the new acoustic transducer is proposed. This transducer is tonpilz type, and made of 1-3 piezoelectric composites as a driving parts. The developed transducer is evaluated the TVR(transmission voltage response) and RVS(receiving voltage sensitivity) characteristics around $4{\sim}14\;kHz$ frequency range and is compared to conventional tonpilz transducer made of solid piezoelectric ceramics as a driving parts. The resonance frequency of the developed transducer is decreased by 30% and the -3 dB bandwidth is increased by 90%, compared to conventional transducer with same dimensions. The value of TVR is decreased by 9 dB and The value of RVS is the same at resonance frequency.
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금속 패터닝과 Blank노광을 이용한 감광성 유리의 미세가공
조재승(Jae-Seung Jo),강형범(Hyung-Bum Kang),윤혜진(Hye-Jin Yoon),김효진(Hyo-Jin Kim),임현우(Hyun-Woo Lim),조시형(Si-Hyeong Cho),임실묵(Sil-Mook Lim) 한국표면공학회 2013 한국표면공학회지 Vol.46 No.3
The simple and cost-effective microfabrication method of photosensitive glass (PSG) using metal patterning and blank exposure was proposed. Conventional photolithography for micromachining of PSG needs a costly quartz mask which has high transmittance as an optical property. However, in this study the process was improved through the combination of micro-patterned Ti thin film and blank UV exposure without quartz mask. The effect of UV exposure time as well as the DHF etching condition was investigated. UV exposure test was performed within the range from 3 min to 9 min. The color and etch result of PSG exposed for 5 min were the most clear and effective to etch more precisely, respectively. The etching results of PSG in diluted hydrofluoric acid (DHF) with a concentration of 5, 10, 15 vol% were compared. The effect on the side etch was insignificant while the etch rate was proportional as the concentration increased. 10 vol% DHF results not only high etch rate of 75 μm/min also lower side etch value after PSG etching. This method facilitates the microfabrication of PSG with various patterns and high aspect ratio for applying to advanced applications.
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