• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.11
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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.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.106-106
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• 2015

In this study, we investigated electrochemically formed nanotube shape on ternary Ti-25Ta-xHf alloys with Hf contents. Ti-25Ta-xHf (x=0~15 wt.%) alloys were manufactured by vacuum arc-melting furnace. The obtained ingots were homogenized in an argon atmosphere at $1050^{\circ}C$ for 2h and then water quenching. The specimens were cut from ingots to 4 mm thickness and first ground and polished using SiC paper (grades from #100 to #2000). The anodization treatments on Ti-25Nb-xHf alloys were carried out at room temperature for experiments. The formation of nanotubular film was conducted by electrochemical method in mixed electrolytes with 1 M $H_3PO_4$ + 0.8 wt. % NaF at 30 V for 2 h. The morphologies of nanotube depended on the Hf content in Ti-25Ta-xHf ternary system.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.89-93
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• 2015

Ion-beam irradiation(IB) on $HfO_2$ surface induced high-performance liquidcrystal(LC) driving at a 1-V threshold with vertical alignment of liquid crystals(LC). The high-k materials Atomic layer deposition was used to obtain LC orientation on ultrathin and high-quality films of $HfO_2$ layers. To analyze surface morphological transition of $HfO_2$ which can act as physical alignment effect of LC, atomic force microscopy images are employed with various IB intensities. The contact angle was measured to elucidate the mechanism of vertical alignment of LC on $HfO_2$ with IB irradiation. Contact angle measurement show the surface energy changes via IB intensity increasing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.382-382
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• 2010

The etch characteristics of the $HfAlO_3$ thin films and selectivity of $HfAlO_3$ to $SiO_2$ in $Cl_2/BCl_3$/Ar plasma were investigated in this work. The maximum etch rate was 108.7 nm/min and selectivity of $HfAlO_3$ to $SiO_2$ was 1.11 at $Cl_2$(3sccm)/$BCl_3$(4sccm)/Ar(16sccm), RF power of 500 W, DC-bias voltage of - 100 V, process pressure of 1 Pa and substrate temperature of $40^{\circ}C$. As increasing RF power and DC-bias voltage, etch rates of the $HfAlO_3$ thin films increased. Whereas as decreasing of the process pressure, those of the $HfAlO_3$ thin films were increased. The chemical reaction on the surface of the etched the $HfAlO_3$ thin films was investigated with X-ray photoelectron spectroscopy (XPS).

• Journal of Magnetics
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• v.13 no.4
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• pp.115-119
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• 2008

The authors predicted that $Co_2HfSi$, a $Co_2$-based full Heusler alloy, is being a half-metallic ferromagnet by first-principles calculations using the all electron full-potential linearized augmented plane wave method which adopts the generalized gradient approximation. The integer value of the calculated total magnetic moment of 2.00 ${\mu}_B$ per formula unit and a spin gap of 0.69 eV in spin down state confirmed the half-metallicity of bulk $Co_2HfSi$. For the $Co_2HfSi$(001) surface, we considered two possible surface terminations, namely, Co terminated and HfSi terminated surfaces. It was found that half-metallicity was retained at the HfSi-terminated surface but not at the Co-terminated surface. The magnetic moment of surface Co atoms in the Co-terminated surface was slightly lower than that of Co atoms in deep inner-layers, whereas the magnetic moments of Hf and Si atoms at the HfSi-terminated surface were almost same as those in deep inner-layers.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.3
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• pp.182-187
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• 2011

In this paper, PBTI characteristics of NMOSFETs with La incorporated HfSiON and HfON are compared in detail. The charge trapping model shows that threshold voltage shift (${\Delta}V_{\mathrm{T}}$) of NMOSFETs with HfLaON is greater than that of HfLaSiON. PBTI lifetime of HfLaSiON is also greater than that of HfLaON by about 2~3 orders of magnitude. Therefore, high charge trapping rate of HfLaON can be explained by higher trap density than HfLaSiON. The different de-trapping behavior under recovery stress can be explained by the stable energy for U-trap model, which is related to trap energy level at zero electric field in high-k dielectric. The trap energy level of two devices at zero electric field, which is extracted using Frenkel-poole emission model, is 1,658 eV for HfLaSiON and 1,730 eV for HfLaON, respectively. Moreover, the optical phonon energy of HfLaON extracted from the thermally activated gate current is greater than that of HfLaSiON.

• Journal of the Semiconductor & Display Technology
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• v.20 no.1
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• pp.113-117
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• 2021

A composite active layer was designed based on graphene quantum dots, which is a low-dimensional structure, and a heterogeneous active layer of graphene quantum dots was applied to the interfacial defect structure to overcome the limitations. Increasing to 1.5~3.5 wt % PVP GQD, Vf changed from 2.16 ~ 2.72 V. When negative deflection is applied to the lower electrode, electrons travel through the HfOx/ITO interface. The Al + ions are reduced and the device dominates at low resistance. In addition, as the PVP GQD concentration increased, the depth of the interfacial defect decreased, and the repetition of appropriate electrical properties was confirmed through Al and HfOx/ITO. The low interfacial defects help electrophoresis of Al+ ions to the PVP GQD layer and the HfOx thin film. A local electric field increase occurred, resulting in the breakage of the conductive filament in the defect.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.158-159
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• 2007

반도체 소자의 공정에 있어서 device scaling으로 인한 게이트 산화막 대체 유전체 (high-k)의 공정 개발 확보 방안 필요하다. 본 논문에서는 $Cl_2$/Ar 유도 결합 플라즈마를 이용하여 $HfO_2$ 박막을 식각하였다. $Cl_2$(80 %)/Ar(20 %)의 가스비, 600 W의 RF 전력, -150 V의 직류 바이어스 전압, 20 sccm의 총 가스유랑, 15 mTorr의 압력에서 15.4 nm/min의 최대 식각률을 얻을 수 있었다. 식각 된 $HfO_2$ 박막 표면을 XPS 분석한 결과 Hf와 O는 Cl 라디칼과 반응을 하여 높은 휘발성을 보이지만 Hf-O의 안정된 결합으로 인하여 이온에 의한 스퍼터링 효과에 의해서 식각된다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.48-48
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• 2009

최근 빠른 동작속도와 고 집적도를 얻기 위해 metal oxide semiconductor field effect transistor (MOSFET) 의 크기는 계속 해서 줄어들고 있다. 동시에 게이트의 절연층도 얇아지게 된다. 절연층으로 사용되는 $SiO_2$ 의 두께가 2nm 이하로 얇아 지게 되면 터널링에 의해 누설 전류가 발생하게 된다. 이 문제를 해결하기 위해 $SiO_2$ 를 대체할 고유전체 물질의 연구가 활발하다. 고유전체 물질 중에는 $ZrO_2,\;Al_2O_3,\;HfO_2$ 등이 많이 연구 되어 왔다. 하지만 유전상수 이외에 band gap energy, thermodynamic stability, recrystallization temperature 등의 특성이 좋지 않아 대체 물질로 문제점이 있다. 이를 보안하기 위해 산화물을 합금과 결합시키면 서로의 장점들이 합쳐져 기준들을 만족하는 물질을 만들 수 있고 $HfAlO_3$가 그 중 하나이다. Al를 첨가하는 이유는 문턱전압을 낮추기 위해서다. $HfAlO_3$는 유전상수 18.2, band gap energy 6.5 eV, recrystallization temperature 800 $^{\circ}C$이고 열역학적 특성이 안정적이다. 게이트 절연층은 전극과 기판사이에 적층구조를 이루고 있어 이방성인 드라이 에칭이 필요하고 공정 중 마스크물질과의 선택비가 높아야한다. 본 연구는 $HfAlO_3$박막을 $BCl_3/Ar,\;N_2/BCl_3/Ar$ 유도결합 플라즈마를 이용해 식각했다. 베이스 조건은 RF Power 500 W, DC-bias -100 V, 공정압력 15 mTorr, 기판온도 40 $^{\circ}C$ 이다. 가스비율, RF Power, DC-bias, 공정 압력에 의한 마스크물질과 의 선택비를 알아보았다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.197-197
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• 2016

Commercially pure titanium (CP Ti) and Ti-6Al-4V alloys have been widely used for biomedical applications. However, the use of the Ti-6Al-4V alloy in biomaterial is then a subject of controversy because aluminum ions and vanadium oxide have potential detrimental influence on the human body due to vanadium and aluminum. Hence, recent works showed that the synthesis of new Ti-based alloys for implant application involves more biocompatible metallic alloying element, such as, Nb, Hf, Zr and Mo. In particular, Nb and Hf are one of the most effective Ti ${\beta}-stabilizer$ and reducing the elastic modulus. Plasma electrolyte oxidation (PEO) is known as excellent method in the biocompatibility of biomaterial due to quickly coating time and controlled coating condition. The anodized oxide layer and diameter modulation of Ti alloys can be obtained function of improvement of cell adhesion. Manganese(Mn) plays very important roles in essential for normal growth and metabolism of skeletal tissue in vertebrates and can be detected as minor constituents in teeth and bone. Radio frequency(RF) magnetron sputtering in the various PVD methods has high deposition rates, high-purity films, extremely high adhesion of films, and excellent uniform layers for depositing a wide range of materials, including metals, alloys and ceramics like a hydroxyapatite. The aim of this study is to research the Mn coatings on the micro-pore formed Ti-29Nb-xHf alloys by RF-magnetron sputtering for dental applications. Ti-29Nb-xHf (x= 0, 3, 7 and 15wt%, mass fraction) alloys were prepared Ti-29Nb-xHf alloys of containing Hf up from 0 wt% to 15 wt% were melted by using a vacuum furnace. Ti-29Nb-xHf alloys were homogenized for 2 hr at $1050^{\circ}C$. Each alloy was anodized in solution containing typically 0.15 M calcium acetate monohydrate + 0.02 M calcium glycerophosphate at room temperature. A direct current power source was used for the process of anodization. Anodized alloys was prepared using 270V~300V anodization voltage at room. Mn coatings was produced by RF-magnetron sputtering system. RF power of 100W was applied to the target for 1h at room temperature. The microstructure, phase and composition of Mn coated oxide surface of Ti-29Nb-xHf alloys were examined by FE-SEM, EDS, and XRD.