• 한국전기전자재료학회논문지
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• 제26권11호
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• pp.821-825
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• 2013

Effect of multi-stacked layer (MSL), 0.1 mol (M) and 0.3 mol (M) hafnium oxide ($HfO_2$) alignment layers were fabricated via a solution-process for LCs orientation. The solutions were spin-coated and annealed in a furnace. MSL consists of three sub-layers using 0.1 M solution, mono-layer (ML) is composed of 0.3 M $HfO_2$ solution. Then ion-beam irradiation was treated with 1.8 keV for 2 min. $HfO_2$-based LC cells were investigated through photographs, pre-tilt angle using crystal rotation method, X-ray photoelectron spectroscopy (XPS) measurement, and surface roughness using atomic force microscopy(AFM) for their characteristic research. Good LC orientation characteristics were observed on MSL $HfO_2$ surface. The LC alignment mechanism on MSL $HfO_2$ and ML $HfO_2$ surfaces was attributed to van der Waals (VDW) interaction between the LC molecular and substrate surface.

• 한국전기전자재료학회논문지
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• 제29권3호
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• pp.135-140
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• 2016

In this study, we developed the solution-processed PMMA-$HfO_x$ hybrid ReRAM devices to overcome the respective drawbacks of organic and inorganic materials. The performances of PMMA-$HfO_x$ hybrid ReRAM were compared to those of PMMA- and $HfO_x$-based ReRAMs. Bipolar resistive switching behavior was observed from these ReRAMs. The PMMA-$HfO_x$ hybrid ReRAMs showed a larger operation voltage margin and memory window than PMMA-based and $HfO_x$-based ReRAMs. The reliability and electrical instability of ReRAMs were remarkably improved by blending the $HfO_x$ into PMMA. An Ohmic conduction path was commonly generated in the LRS (low resistance state). In HRS (high resistance state), the PMMA-based ReRAM showed SCLC (space charge limited conduction). the PMMA-$HfO_x$ hybrid ReRAM and $HfO_x$-based ReRAM revealed the Pool-Frenkel conduction. As a result of flexibility test, serious defects were generated in $HfO_x$ film deposited on PI (polyimide) substrate. On the other hand, the PMMA and PMMA-$HfO_x$ films showed an excellent flexibility without defect generation.

• 대한치과기공학회지
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• 제27권1호
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• pp.19-25
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• 2005

Ti6Al4V alloy have been mainly used as implant materials. Ti-6Al-4V alloy instead of pure Ti is being widely used as biomaterials has some characteristics such as high fatigue strength, tensile strength. But it has been reported recently that vanadium component expresses cytotoxicity and carcinogenicity and aluminium component is related with dementia of Alzheimer type. In order to overcome their detrimental effects, $\beta$-phase stabilizer Nb was chosen in the present study, in addition Ta and Hf were added to Ti-40wt.%Nb alloy to improve its mechanical properties. This paper was described the influence of heat treatment of Ti-40Nb alloys with 2wt%Ta, 2wt%Hf on the mechanical properties. Specimens of Ti alloys were melted in vacuum arc furnace and homogenized at 1050$^{\circ}C$ for 24 hr. and then were aged after solution heat treat at $\alpha+\beta$ and $\beta$ regions. The mechanical properties of Ti alloys were analysed by hardness test, tensile test, elongation test and SEM test. The results can be summarized as follows: 1. The mechanical properties Ti-40wt.%Nb were improved when 2wt.% Ta and 2wt.%Hf were added. 2. The higher tensile strength value and elongation at solution heat treat was higher than solution heat treat and then were aged.

• 한국재료학회지
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• 제31권12호
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• pp.682-689
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• 2021

NbC, HfC, TaC, and their solid solution ceramics have been identified as the best materials for ultrahigh-temperature ceramics. However, their structural stability and elastic properties are mostly unclear. Thus, we investigated structure and elastic properties of (Nb_1-xTa_x)C and (Nb_1-xHf_x)C solid solutions via ab initio calculations. Our calculated results show that the stability of (Nb_1-xTa_x)C and (Nb_1-xHf_x)C increases with the increase of Hf and Ta content, and (Nb_1-xHf_x)C is more stable than (Nb_1-xTa_x)C at the same content of Hf and Ta. The lattice constants decrease with increasing of Hf and Ta content. (Nb_1-xTa_x)C and (Nb_1-xHf_x)C carbides are mechanically stable and brittle. Bulk modulus of (Nb_1-xTa_x)C increases with increasing Ta content. In contrast, bulk modulus of (Nb_1-xHf_x)C decreases with increasing Hf content. Hardness of solid solutions shows the highest values at the (Nb_0.25Ta_0.75)C and (Nb_0.75Hf_0.25)C. In particular, (Nb_0.75Hf_0.25)C shows the highest hardness for the current system. The results indicate that the overall mechanical properties of (Nb_1-xHf_x)C solid solutions are superior to those of (Nb_1-xTa_x)C solid solutions. Therefore, controlling the Hf and Ta element and content of the (Nb_1-xTa_x)C and (Nb_1-xHf_x)C Solid solution is crucial for optimizing the material properties.

• 한국환경농학회지
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• 제27권3호
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• pp.217-224
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• 2008

시설하우스 폐양액 처리를 위한 소형 폐양액처리장치 개발을 위해 소형 폐양액처리장치를 VF-HF, VF-VF, HF-VF 및 HF-HF 조합형으로 구분하여 조합방법별, 여재깊이별 및 폐양액 부하량별로 각각 최적 조건을 조사하였으며, 개발된 시설하우스 폐양액처리장치의 적용성을 검증하기 위해 상기 최적조건하에서 실제 오이, 파프리카 및 딸기 시설하우스에서 배출되는 폐양액의 수처리효율을 조사하였다. 여재 깊이에 따른 오염물질의 수처리 효율은 BOD, COD, SS, T-N 및 T-P 모두에서 깊이가 깊어짐에 따라 수처리효율이 점점 증가하였으며,여재깊이70 cm에서 모든 조합의 BOD, COD 및 SS의 처리효율은 각각 87, 84 및 82% 이상으로 조합방법에 따라 큰 차이 없이 안정적인 수처리 효율을 보였다. T-N 및 T-P의 경우 HF-HF 및 HF-VF 조합형의 처리효율이 타 조합방법에 비해 약간 높았다. 폐양액 부하량에 따른 BOD, COD, SS, T-N 및 T-P의 처리효율은 $150L\;m^{-2}\;day^{-1}{\approx}300L\;m^{-2}\;day^{-1}>450L\;m^{-2}\;day^{-1}$순으로 폐양액의 부하량이 증가함에 따라 수처리 효율이 점점 감소하였다.모든 폐양액 부하량에서의 오염물질 처리효율은HF-VF 및 HF-HF 조합형이 다른 조합형에 비해 높았으며, 특히 총 질소의 경우 HF-HF 조합형이 가장 높은 처리효율을 보였다. 장치의 최적 여재깊이는 70 cm이상이었고, 최적 폐양액 부하이상의 결과를 미루어 볼 때 시설하우스 소형 폐양액처리량은 $300L\;m^{-2}\;day^{-1}$이하이었으며, 최적 조합방법은HF-HF 조합형이었다.

• 센서학회지
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• 제1권2호
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• pp.183-194
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• 1992

실리콘 기판을 HF용액 내에서 양극반응을 시켜 electropolishing법 또는 PSL 형성법으로 센서와 actuator에 유용한 다양한 모양의 실리콘 미세 기계구조를 제조하였다. 미세구조는 시편의 결정면에 관계없이 형성되었으며, 저농도 도핑된 단결정 실리콘이다. $n^{+}/n$ 실리콘 시편을 HF용액(20-48%)내에서 양극반응시켜 $n^{+}$ 영역에 선택적으로 PSL을 형성하였으며, HF농도, 반응전압 및 반응시간에 따른 PSL 형성의 특성을 조사였다. $n^{+}$ 영역에만 PSL이 형성되었으며 PSL의 다공도는 HF 농도 증가에 따라 감소하였으며, 반응전압에는 무관하였다. $n/n^{+}/n$형 구조를 이용하여 미세구조를 제조한 경우, 식각된 실리콘 표면이 균일하고 cusp가 제거되었으며, 미세구조의 두께는 전 영역을 통하여 n-epi.층의 두께로 일정하였다. HF용액(5 wt%)에서의 양극반응과 planar기술을 이용하여 가속도센서를 제조하여 기존의 IC 공정기술과 함께 사용이 가능함을 확인하였다. 또 모터의 회전자, 기어 등의 미세 기계구조를 PSL 형성법으로 제조하고 SEM 사진으로 조사하였다.

• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.389-396
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• 2009

MFI structural zeolite (ZSM-5 or Sililcalite) was treated with HF solution to introduce mesoporous channels in the microporous crystals. Inner mesopore size could be controlled from 2.5 to 3.5 nm by changing the concentration of HF solution. The pore structure of HF-treated MFI zeolite was studied by instrumental analysis. The active Co (III) salen complex monomers were successfully anchored non-covalently on the surfaces of mesoporous MFI-type zeolite. These heterogeneous catalysts could be applied in asymmetric ring opening of terminal epoxides by phenol derivatives. It showed very high enantioselectivity and yield up to 95% in the catalytic synthesis of optically active $\alpha$-aryloxy alcohol compounds.

• 전기전자학회논문지
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• 제23권2호
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• pp.594-598
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• 2019

HfZnO 박막 위 패턴 전사 기법을 이용하여 기존의 러빙법을 대체하는 배향 공정에 대하여 연구하였다. 정렬 패턴은 레이저 간섭 리소그래피를 이용하여 실리콘 웨이퍼 위에 제작하였다. 졸겔 공정을 이용하여 HfZnO 용액을 제작하였고, 유리기판 위에 스핀코팅하였다. 미리 제작한 정렬패턴을 스핀코팅된 HfZnO 위에 올려놓고, $100^{\circ}C$에서 30분간 소성하였다. HfZnO 박막에 평행한 그루브가 형성되었음을 atomic force microscopy 와 scanning electron microscopy로부터 확인할 수 있었다. HfZnO 박막을 이용하여 액정 셀을 제작하였으며, POM 분석으로부터 액정이 균일하게 정렬되었음을 확인할 수 있었다. 액정은 $0.25^{\circ}$의 프리틸트 각을 가졌으며, 수평배향 특성을 보여주었다. 액정 분자는 평행한 그루브에 의한 HfZnO 박막 표면 이방성에 의하여 균일하게 정렬되었음을 확인할 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.318.1-318.1
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• 2016

Hafnium Oxide (HfOx) has been attracted as a promising gate dielectric for replacing SiO2 in gate stack applications. In this paper, Metal-Oxide-Semiconductor (MOS) capacitor with solution processed HfO2 high-k material as a dielectric were fabricated. The solvent using $HfOCl2{\cdot}8H2O$ dissolve in 2-Methoxy ethanol was prepared at 0.3M. The HfOx layers were deposited on p-type silicon substrate by spin-coating at $250^{\circ}C$ for 5 minutes on a hot plate and repeated the same cycle for 5 times, followed by annealing process at 350, 450 and $550^{\circ}C$ for 2 hours. When the annealing temperature was increased from 350 to $550^{\circ}C$, capacitance value was increased from 337 to 367 pF. That was resulted from the higher temperature of HfOx which have more crystallization phase, therefore dielectric constant (k) was increased from 11 to 12. It leads to the formation of dense HfOx film and improve the ability of the insulator layer. We confirm that HfOx layer have a good performance for dielectric layer in MOS capacitors.

• 센서학회지
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• 제22권3호
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• pp.233-237
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• 2013

We fabricated electrolyte-insulator-semiconductor (EIS) devices using a solution process and measured the sensing properties of EIS devices according to the thicknesses of sensing membrane. For high pH sensitivity and better stability properties, we used $SiO_2/HfO_x$ (OH) layer as a sensing membrane. In this work, $HfO_x$ sensing membranes were deposited on 5 nm thick $SiO_2$ buffer layer by spin coater with thicknesses of 15, 31, 42, 55 nm, respectively. As a result, we founded that the thickness of $HfO_x$ sensing membrane affects to sensitivity and chemical stability of EIS device. Especially, the EIS device with 42 nm thick $HfO_x$ membrane showed superior sensing ability in terms of pH-sensitivity, linearity, hysteresis voltage and drift rate characteristics than the other devices. In conclusion, we confirmed that it is possible to improve the sensing ability and the chemical stability properties using optimized thickness of sensing membrane and proper annealing process.