• 전자공학회논문지
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• 제53권12호
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• pp.15-19
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• 2016

매우 큰 사이즈를 가진 multi-finger RF MOSFET의 $S_{11}$-parameter에서 스미스차트의 저항 circle 라인을 벗어나는 kink 현상의 게이트 바이어스 종속 특성이 관찰되었다. 이러한 바이어스 종속성은 $S_{11}$-parameter의 크기와 위상, 입력저항, 입력 커패시턴스의 주파수 응답곡선을 측정하여 최초로 분석되었다. 그 결과 입력 커패시턴스의 크기와 입력저항의 dominant pole과 zero 주파수에 의해 $V_{gs}$ 종속 kink 현상이 크게 변하는 것을 알 수 있다. $V_{gs}=0V$일 때 매우 적은 $S_{11}$-parameter 위상차와 입력저항의 높은 pole 주파수에 의해 고주파영역에서 kink 현상이 나타난다. 하지만 $V_{gs}$가 높아지면 $S_{11}$-parameter 위상차가 크게 증가하고 pole 주파수가 낮아져 저주파영역에서 kink 현상이 발생하게 된다.

• 한국자기학회지
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• 제27권1호
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• pp.30-34
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• 2017

본 연구에서는 교환 결합력을 갖는 강자성/반강자성(AF) 박막에서 단자구 모델을 사용하여 교환 바이어스($H_{ex}$)의 각도 의존성을 계산하였으며, NiFe/MnIr 박막에서 측정한 결과와 비교 분석하였다. AF층 두께가 임계 두께 이상에서($t_{AF}$ > $t_c$) 계산한 $H_{ex}$의 각도 의존성은 전형적인 일방 이방성 특성을 보였으나, $0.5t_c$ < $t_{AF}$ < $t_c$에서는 $90^{\circ}$ 근처의 특정한 각도에서 AF 스핀의 고정에 의한 독특한 $H_{ex}$의 각도 의존성을 보였다. NiFe/MnIr(20 nm) 박막에서 측정한 $H_{ex}$의 각도 의존성은 전형적인 일방 이방성 특성을 보였으나, NiFe/MnIr(4 nm) 박막에서는 일방 이방성 특성과 AF 스핀의 고정에 의한 특성이 혼합된 결과를 보였으며, 이는 다결정 구조를 갖는 MnIr의 입도 분포 특성으로 설명되어짐을 알 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.436-436
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• 2011

Recently, spintronic devices with submicron structures are widely investigated to take advantage of their unique micromagnetic properties. In this work, we study the temperature dependence of exchange bias in bilayer anti-dot arrays made by depositing Co (40 nm)/Ni (5 nm) ferromagnetic bilayer on Si substrate to form anti-dot arrays with a diameter $1{\mu}m$. The anti-dot patterning was done only for the upper Co layer, while the Ni underlayer was kept unperforated. The temperature dependences of magnetoresistance (MR) and exchange bias were studied along magnetic easy and hard axes. The in-plane MR measurements were performed using a physical-property measurement system (PPMS ; Quantum Design Inc.) at various temperatures. The standard in-line four-point probe configuration was used for the electrical contacts. As temperature was varied, the MR data were obtained in which in-plane field (H=3 kOe) was applied in the directions along the hard and the easy axes with respect to the lattice plane. The temperature dependences of magnetic anisotropy and exchange bias were also studied along the magnetic easy and hard axes. As temperature decreases, the single peak splits into two peaks. While no exchange bias was observed along the magnetic easy axis, the exchange bias field steadily increased with decreasing temperature along the magnetic hard axis. These results were interpreted in connection with the magnetic anisotropy and the effect of the anti-dots in pinning domain wall motion along the respective direction.

• ETRI Journal
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• 제15권2호
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• pp.11-25
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• 1993

Interface trap densities at gate oxide/silicon substrate ($SiO_2/Si$) interfaces of metal oxide semiconductor field-effect transistors (MOSFETs) were determined from the substrate bias dependence of the subthreshold slope measurement. This method enables the characterization of interface traps residing in the energy level between the midgap and that corresponding to the strong inversion of small size MOSFET. In consequence of the high accuracy of this method, the energy dependence of the interface trap density can be accurately determined. The application of this technique to a MOSFET showed good agreement with the result obtained through the high-frequency/quasi-static capacitance-voltage (C-V) technique for a MOS capacitor. Furthermore, the effective substrate dopant concentration obtained through this technique also showed good agreement with the result obtained through the body effect measurement.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.825-828
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• 1992

In this paper, a Hybrid method for an effective channel length($L_{eff}$) on lightly doped drain(LDD) MOSFET's is proposed. In order to investigate the difference of the gate bias and substrate bias defendence of the $L_{eff}$ among various LDD structures, the $L_{eff}$ of the LDD's are extensively examined using simulations and measurement. one group is proposed for conventional MOSFET and the other group Is proposed for LDD MOSFET. It is shown that the $V_{bs}$-dependence of the n-region is different from $V_{gs}$-dependence of it.

• Journal of the Optical Society of Korea
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• 제15권3호
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• pp.237-243
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• 2011

Thermal characteristics, such as diffusivity and temperature induced change in the fiber mode index of rotation sensing fiber coil are critical factors which determine the time varying, thermo-optically induced bias drift of interferometric fiber-optic gyroscopes (IFOGs). In this study, temperature dependence of the transient effect is analyzed in terms of the thermal characteristics of the fiber coil at three different temperatures. By applying an analytic model to the measured bias in the experiments, comprehensive thermal factors of the fiber coil could be extracted effectively. The validity of the model was confirmed by the fact that the extracted values are reasonable results in comparison with well known properties of the materials of the fiber coil. Temperature induced changes in the critical factors were confirmed to be essential in compensating the transient effect over a wide temperature range.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.173-173
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• 1999

The initial growth mode of Nb on Ag(110) in sub-monolayer region is studied using Scanning Tunneling microscopy. E-beam evaporated Nb is deposited onto the substrate at RT, and STM measurements are carried out at RT and 78K. With Nb being immiscible in bulk Ag, 3D islands formation begins at early stage and no particular ordered structure is found. At very low coverages, however, many interesting phenomena are observed in association with Nb clusters. Small Nb clusters as deposited displays very strong size dependence against atom-manipulation by the STM tip. In addition, the apparent corrugation of clusters below the critical size exhibits dramatic dependence on the imaging bias, disappearing completely over a wide range of the bias. Possible physical mechanism responsible for such behavior will be discussed.

• 한국광학회지
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• 제7권2호
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• pp.167-173
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• 1996

본 논문에서 STN LCD의 구동전압에 따른 응답특성을 조사하였다. 네 가지 STN 액정 셀로써 여러 인가전압에 대한 스위칭 시간을 측정하였다. 또한 해석식으로 설명이 안되는 바이어스 전압의 스위칭 시간에 대한 영향을 실험을 통해 알아보았다. 그리고 수치해석적 방법으로 수한 계산결과와 비교하므로써, 계산결과가 바이어스 전압에 따른 실험결과와 비교적 잘 일치함을 알 수 있었다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.229-229
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• 2003

Enhancement of the exchange bias and optimization of the structure have been the focus that many researchers studied, recently [1]. In this report, magnetic properties of MTJs with structure of Si/Ta (5)/Cu (10)/ Ta (5)/ Ni$\sub$80/Fe$\sub$20/ Cu (5)/ Mn$\sub$75Ir$\sub$25/ (10)/ Co$\sub$70/Fe$\sub$30/ (2.5)/ Al-O (1.5)/ Co$\sub$70/Fe$\sub$30/ (2.5)/ Ni$\sub$80/Fe$\sub$20/ (t)/ Ta (5) (t=0,10, 30, 60 and 100 nm, respectively) were investigated. The relationship between the structure and magnetic parameters of interfacial exchange coupling and interlayer coupling in as-deposited and annealed junctions was studied. The temperature dependence of exchange coupling was considered.

• 한국자기학회지
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• 제26권2호
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• pp.50-54
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• 2016

본 연구에서는 교환 결합력을 갖는 CoFe/MnIr 박막 재료의 각도에 따른 강자성 공명 선폭 변화 특성을 분석하였다. 선폭의 최대 및 최소값은 교환 결합력에 의한 일방 이방성의 자화 곤란축 및 용이축 방향에서 각각 관측되었으며, 고정된 MnIr의 스핀에 의한 교환 바이어스 자기장의 각도 의존성과 일치하였다. 따라서, 최대 선폭은 고정된 MnIr 스핀의 반대 방향에서 자기장 방향으로 꼬여있는(twist) CoFe의 자화에 기인한다. 한편, CoFe 단일 박막에 비하여 증가된 최소 선폭은 각도 의존성이 없는 회전 이방성 자기장과 관련되며, 선폭 증가의 원인은 MnIr 입도의 자화 용이축 분포 특성으로 설명된다.