• Journal of Magnetics
• /
• 제10권3호
• /
• pp.122-127
• /
• 2005

New classes of LC resonators for micro magnetic sensor device were proposed and fabricated. The first type LC resonator (Type I) consists of a small piece of microwire and two cylindrical electrodes at the end of the microwire without direct contact to its ferromagnetic core. In type I resonator the ferromagnetic core of the microwire and cylindrical electrodes act as an inductor and two capacitors respectively to form a LC circuit. The second type LC resonator (Type II) consists of a solenoidal micro-inductor with a bundle of soft magnetic microwires as a core. The solenoidal micro-inductors fabricated by MEMS technique were $500\sim1,000\;\mu{m}$ in length with $10\sim20$ turns. A capacitor is connected in parallel to the micro-inductor to form a LC circuit. A tiny glass coated $CO_{83.2}B_{3.3}Si_{5.9}Mn_{7.6}$ microwire was fabricated by a glass-coated melt spinning technique. A supergiant magneto-impedance effect was found in a type I resonator as much as 400,000% by precise tuning frequency at around 518.51 MHz. In type II resonator the changes of inductance as a function of external magnetic field in micro-inductors with properly annealed microwire cores were varied as much as 370%. The phase angle between current and voltage was also strongly dependent on the magnetic field. The drastic increments of magnetoimpedance at near the resonance frequency were observed in both types of LC resonators. Accordingly, the sudden change of the phase angle, as large as $180^{\circ}C$, evidenced the occurrence of the resonance at a given external magnetic field.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
• /
• pp.454-454
• /
• 2014

Silicon microwire array is one of the promising platforms as a means for developing highly efficient solar cells thanks to the enhanced light trapping efficiency. Among the various fabrication methods of microstructures, deep reactive ion etching (DRIE) process has been extensively used in fabrication of high aspect ratio microwire arrays. In this presentation, we show precisely controlled Si microwire arrays by tuning the DRIE process conditions. A periodic microdisk arrays were patterned on 4-inch Si wafer (p-type, $1{\sim}10{\Omega}cm$) using photolithography. After developing the pattern, 150-nm-thick Al was deposited and lifted-off to leave Al microdisk arrays on the starting Si wafer. Periodic Al microdisk arrays (diameter of $2{\mu}m$ and periodic distance of $2{\mu}m$) were used as an etch mask. A DRIE process (Tegal 200) is used for anisotropic deep silicon etching at room temperature. During the process, $SF_6$ and $C_4F_8$ gases were used for the etching and surface passivation, respectively. The length and shape of microwire arrays were controlled by etching time and $SF_6/C_4F_8$ ratio. By adjusting $SF_6/C_4F_8$ gas ratio, the shape of Si microwire can be controlled, resulting in the formation of tapered or vertical microwires. After DRIE process, the residual polymer and etching damage on the surface of the microwires were removed using piranha solution ($H_2SO_4:H_2O_2=4:1$) followed by thermal oxidation ($900^{\circ}C$, 40 min). The oxide layer formed through the thermal oxidation was etched by diluted hydrofluoric acid (1 wt% HF). The surface morphology of a Si microwire arrays was characterized by field-emission scanning electron microscopy (FE-SEM, Hitachi S-4800). Optical reflection measurements were performed over 300~1100 nm wavelengths using a UV-Vis/NIR spectrophotometer (Cary 5000, Agilent) in which a 60 mm integrating sphere (Labsphere) is equipped to account for total light (diffuse and specular) reflected from the samples. The total reflection by the microwire arrays sample was reduced from 20 % to 10 % of the incident light over the visible region when the length of the microwire was increased from $10{\mu}m$ to $30{\mu}m$.

• 마이크로전자및패키징학회지
• /
• 제28권1호
• /
• pp.67-71
• /
• 2021

본 연구에서는 금속 와이어를 촉매로 화학기상증착법을 이용하여 그래핀을 합성하고 구조 및 전기적 특성 변화를 분석하였다. 구리와 니켈의 탄소에 대한 용해도 차이로 인해 구리와이어에서는 단층 그래핀이 성장하였고, 니켈와이어의 표면에는 다층 그래핀이 성장되었다. 또한. 고온의 그래핀 성장 조건에서 구리와 니켈의 재결정화를 통해 결정립의 크기가 증가한 것을 확인하였다. 표면에 그래핀이 합성된 구리와이어의 경우, 최대전류허용치는 1.91×105 A/㎠으로 합성 전 구리와이어에 비해 약 27% 향상되었다. 이와 유사하게, 다층 그래핀이 합성된 니켈와이어의 경우에도 최대전류 허용치는 순수한 니켈와이어 대비 약 36% 향상된 4.41×104 A/㎠으로 측정되었다. 이러한 그래핀/금속 복합소재의 우수한 전기적 특성은 고전류를 요구하는 소자 및 부품에서 안정적인 전기적 흐름을 공급하는데 기여할 수 있을 것이다.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2000년도 International Symposium on Magnetics The 2000 Fall Conference
• /
• pp.502-503
• /
• 2000

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
• /
• pp.418-418
• /
• 2008

The electrochemical etching of silicon in HF-based solutions is known to form various types of porous structures. Porous structures are generally classified into three categories according to pore sizes: micropore (below 2 nm in size), mesopore (2 ~ 50 nm), and macropore (above 50 nm). Recently, the formation of macropores has attracted increasing interest because of their promising characteristics for an wide scope of applications such as microelectromechanical systems (MEMS), chemical sensors, biotechnology, photonic crystals, and photovoltaic application. One of the promising applications of macropores is in the field of MEMS. Anisotropic etching is essential step for fabrication of MEMS. Conventional wet etching has advantages such as low processing cost and high throughput, but it is unsuitable to fabricate high-aspect-ratio structures with vertical sidewalls due to its inherent etching characteristics along certain crystal orientations. Reactive ion dry etching is another technique of anisotropic etching. This has excellent ability to fabricate high-aspect-ratio structures with vertical sidewalls and high accuracy. However, its high processing cost is one of the bottlenecks for widely successful commercialization of MEMS. In contrast, by using electrochemical etching method together with pre-patterning by lithographic step, regular macropore arrays with very high-aspect-ratio up to 250 can be obtained. The formed macropores have very smooth surface and side, unlike deep reactive ion etching where surfaces are damaged and wavy. Especially, to make vertical microwire or nanowire arrays (aspect ratio = over 1:100) on silicon wafer with top-down photolithography, it is very difficult to fabricate them with conventional dry etching. The electrochemical etching is the most proper candidate to do it. The pillar structures are demonstrated for n-type silicon and the formation mechanism is well explained, while such a experimental results are few for p-type silicon. In this report, In order to understand the roles played by the kinds of etching solution and mask patterns in the formation of microwire arrays, we have undertaken a systematic study of the solvent effects in mixtures of HF, dimethyl sulfoxide (DMSO), iso-propanol, and mixtures of HF with water on the structure formation on monocrystalline p-type silicon with a resistivity with 10 ~ 20 $\Omega{\cdot}cm$. The different morphological results are presented according to mask patterns and etching solutions.

• 한국자기학회지
• /
• 제17권3호
• /
• pp.141-146
• /
• 2007

MEMS 공정기법을 적용하여 새로운 형태의 LC 공진기형 자기센서를 제작하였다. 이 마이크로 LC 공진기는 솔레노이드형 마이크로인덕터에 연자성 마이크로와이어를 코어로 삽입하고 여기에 콘덴서를 병렬로 연결하여 구성하였다. 코어 자성 물질은 melt spinning 법으로 제조한 유리가 코팅된 $Co_{83.2}B_{3.3}Si_{5.9}Mn_{7.6}$ 마이크로와이어이다. 코어물질의 연자성을 개선하기 위하여 $150^{\circ}C$, $200^{\circ}C,\;250^{\circ}C,\;300^{\circ}C$ 등 여러 온도에서 1시간씩 진공 열처리하였다. MEMS 공정으로 제작된 솔레노이형 마이크로인덕터는 길이가 $500{\sim}1,000{\mu}m$ 이며 감은수는 $10{\sim}20$회이다. 외부자기장에 따른 본 마이크로인덕터의 최대 인덕턴스 변화율은 370%이었다. 초연자성 마이크로와이어의 투자율이 외부자기장에 따라 급격히 변하기 때문에 인덕턴스변화율이나 LC 공진기의 자기임피던스 변화율(MIR)이 급속하게 변한다. 최대감도를 얻기 위해서 MIR 곡선은 정교하게 조절할 수 있다. 마이크로인덕터와 멀티바이브 레어터 회로로 구성된 원형 자기센서소자를 제작하여 시험동작을 하는데 성공하였다.

• Journal of Magnetics
• /
• 제7권4호
• /
• pp.160-164
• /
• 2002

A new discovery of the super-giant magneto-impedance (SGMI) effect was found out in a LC-resonator consisted of a glass-coated amorphous $CO_{83.2}B_{3.3}Si_{5.9}Mn_{7.6}$ microwire. The measurement was carried out at high frequency range from 100 MHz up to 1 GHz of an ac-current flowing along the wire and at varying axial dcmagnetic field in its range of $\pm$120 Oe. The wires, about 16${\mu}m$ in diameter, were fabricated by a glass-coated melt spinning technique. The shape of the impedance curves plotted vs. a dc-field is changing dramatically with the frequency. The phase angle was also strongly dependent on this field. The external dc-magnetic field changes the circumferential permeability as well as the penetration depth, both in turn change the impedance of the sample. The drastic increments of SGMI at high frequency can be understood in terms of the LC-resonance phenomena. The sudden change of the phase angle, as large as $180^{\circ}$ evidenced the occurrence of the resonance at a given intensity of the external dc-field. The maximum ratio of SGMI reached in the experiment by precise tuning frequency equals 450,000％ at the frequency of around 551.9075 MHz.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2007년도 The 1st International Symposium on Advanced Magnetic Materials
• /
• pp.143.1-143.1
• /
• 2007

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
• /
• pp.210-210
• /
• 2011

Ultrasmall electodes are of great importance for basic electrochemical study and applications. We fabricated single crystal (111) Au nanowire (NW) by growth mechanism on substrate without any catalyst. Consequently, these high aspect NW combined with tungsten microwire and the electrodes having NW tip on their end were obtained. These single crystal Au (111) NWs were characterized by electron microscope and electrochemical analysis. We show that precise electrochemical measurement could be possible on these NW electrode by obtaining underpotential deposition (UPD) and ferricyanide CV profiles on the electrode. The immersed depth of electrode into solution was controlled in micrometer scale by piezo-driven manipulator.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 초전도 자성체
• /
• pp.76-78
• /
• 2002

The influence of laser annealing on gaint magnetoimpedance effect of glass-covered Co-based amorphous microwires is investigated by illuminating pulse Nd:YAG laser on the etched microwires. The maxium GMI ratio reaches maximum of around 85 % at the frequency of 5 MHz for the sample iluminated by the pulse with laser energy fo 132 mJ/pulse.