• Journal of the Korean Magnetics Society
• /
• v.12 no.5
• /
• pp.163-167
• /
• 2002

In order to study the temperature dependence of the magnetostatic wave modes for an YIG thin film, grown by a liquid phase epitaxy method, The ferromagnetic resonance was performed by an FMR spectrometer in the temperature range -140$\^{C}$∼200$\^{C}$. The magnetostatic surface wave and backward volume wave modes show periodic excitations in parallel configuration. The resonance fields of all modes and intensities decreased with decreasing the temperature. All magnetostatic modes can be well explained by the Walker and Damon-Eshbach theory. The calculated saturation magnetization Ms of the YIG thin film was increased with decreasing the temperature. The line widths of magnetostatic modes changed in various trends with decreasing the temperature.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.274-274
• /
• 2012

We have researched on controlling an electron temperature and a plasma collision frequency to study the effect of collisions on helicon plasmas. So, we have designed and constructed an electron cyclotron resonance (ECR) heating system in the helicon device as an auxiliary heating source. Since then, we have tried to optimize experimental designs such as a magnetic field configuration for ECR heating and 2.45GHz microwave launching system for its power transfer to the plasma effectively, and have characterized plasma parameters using a Langmuir probe. For improving an efficiency of the ECR heating with R-wave in the helicon plasma, we would understand an effect of R-wave propagation with ECR heating in the helicon plasma, because the efficiency of ECR heating with R-wave depends on some factors such as electron temperature, electron density, and magnetic field gradient. Firstly, we calculate the effect of R-wave propagation into the ECR zone in the plasma with those factors. We modify the magnetic field configuration and this system for the effective ECR heating in the plasma. Finally, after optimizing this system, the plasma parameters such as electron temperature and electron density are characterized by a RF compensated Langmuir probe.

• ETRI Journal
• /
• v.21 no.2
• /
• pp.1-8
• /
• 1999

We analyze the characteristics of a coaxial-to-waveguide transition based on the finite difference time domain (FDTD) method with the cylindrical to rectangular cell interpolation scheme. The scheme presented in this paper is well suited for the analysis of a microwave device with a probe near waveguide discontinuity because perfect TEM mode can be generated inside the coaxial cable by using the cylindrical cell. The scattering parameters of a designed Ka-band transition are evaluated and compared with those of commercially available software, High Frequency Structure analysis Simulator (HFSS) and measured data. There exists good agreement between the measured and calculated data. In order to prove an accuracy of the interpolation scheme, a coaxial to waveguide transition with a disk-loaded probe is analyzed by the present approach and the results of this analysis are compared with measured data. Comparison shows that our results match very closely to those of measurement and other approaches. The method presented in this paper can be applied to analyze the characteristics of a probe excited cavity, coaxial waveguide T-Junctions, and so on.

• Journal of information and communication convergence engineering
• /
• v.15 no.2
• /
• pp.112-116
• /
• 2017

In this work, we demonstrated a low noise and high linearity low noise amplifier (LNA) monolithic microwave integrated circuit (MMIC) with novel active bias circuit for LTE applications. The device technology used in this work relies on a process involving a $0.25-{\mu}m$ GaAs pseudomorphic high electron mobility transistor (PHEMT). The LNA MMIC with a novel active bias circuit has a small signal gain of $19.7{\pm}1.5dB$ and output third order intercept point (OIP3) of 38-39 dBm in the frequency range 1.75-2.65 GHz. The noise figure (NF) is less than 0.58 dB over the full bandwidth. Compared with the characteristics of the LNA MMIC without using the novel active bias circuit, the OIP3 is improved about 2-3 dBm. The small signal gain and NF showed no significant change after using the active bias circuit. The novel active bias circuit indeed improves the linearity performance of the LNA MMIC without degradation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.11 no.3
• /
• pp.153-163
• /
• 1986

GaAs, one of the III-V compounding semicondnctors, has been widely employed as base materials for the fabrication of the ultra-high-speed devices in the filelds of DBS, optical communications, MMIC'S and digital IC'S. There have been some reports on 4Kx4bit SRAM by D/E MESFET'S, 4K bit SRAM by HEMT'S, and receiver front ends for X-band by MMIC technologies, respectively. This paper reviews GaAs materials, wafer fabrication processes, device applications, and design aspects, and, finally, descusses the future of the ultra-high-spped-devices.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07b
• /
• pp.768-771
• /
• 2004

Pb0.5,Sr0.5TiO3(PST) thin films were deposited on Si with MgO (100) buffer layer by the alkoxide-based sol-gel method. Structural and dielectric properties of PST thin films for the tunable microwave device applications were investigated. For the MgO/Si buffer layer, the PST thin films exhibited highly (100) orientation. The MgO buffer layer affects the stress state of the (100)-oriented PST thin films. The dielectric constant, tunability, and FOM of the highly (100)-oriented PST thin film increased with increasing annealing temperature due to the decrease in lattice distortion. The differences in dielectric properties may be attributed to the change in the film stress. The dielectric constants, dielectric loss and tunability of the PST thin films deposited on the MgO/Si substrates measured at 10 kHz were 822, 0.025, and 80.1%, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07b
• /
• pp.794-797
• /
• 2004

The object of investigation is represented by PbxSrl-xTiO3(PST) thin films, which were fabricated by the alkoxide-based sol-gel method on Pt/Ti/SiO2/Si substrate. We have investigated both structural and dielectric properties of PST thin films aimed to tunable microwave device applications as a function of Pb/Sr ratio. PST thin films showedtypical polycrystalline structure with a dense microstructure without secondary phase formation. Dielectric properties of PST films were found as strongly dependent on Pb/Sr composition ratio. Increasing of Pb content leads to simultaneous increasing of both dielectric constant and dielectric loss characteristics of PST films. The figure of merit (FOM) Parameter (FOM : (%) tunability / tan (%)) reached a maximal value of 27.5 corresponding to Pb/Sr ratio of 40/60. The tunability increased with increasing Pb content. The dielectric constants, dielectric loss and tunability of the PST thin films at Pb/sr ratio of 40/60 measured at 100 kHz were 335, 0.0174 and 47.89 %, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07a
• /
• pp.219-222
• /
• 2003

In this paper, we designed a Ku-band BPF(Band Pass Filter) by microstrip line that most usually used a microwave device design and fabrication. Here a substrate of designed BPF were silicon substrate(${\varepsilon}_r=11.8$), and metal line was copper and silver/copper structure. And a configration of BPF was used hairpin pattern. A center frequency of designed BPF was 10GHz and their FBW(Fractional Band Width) was 20%(2GHz). It presented simulated results obtained for a 10GHz filter which yields an insertion loss of 0.1dB that ripple value related chebyshev reponse. Finallt we tried to make that a 30dB attenuation frequency was 20% of center frequency.

• Journal of Korean Vacuum Science & Technology
• /
• v.3 no.1
• /
• pp.38-42
• /
• 1999

Using the LOCOS process, we have fabricated the lateral type polysilicon field emission triodes with poly-Si/oxide/Si structure and investigated their current-voltage characteristics for three biasing modes of operation. The fabricated devices exhibit excellent electrical performances such as a relatively low turn-on anode voltage of 14 V at VGC = 0V, a stable and high emission current of 92${\mu}$A/triode over 90 hours, a small gate leakage current of 0.23 ${\mu}$A/triode and an outstanding transconductance of 57${\mu}$S/5triodes at VGC = 5V and VAC = 26V. these superior electrical operation is believed to be due to a large field enhancement effect, which is related to the sharp cathode tips produced by the LOCOS process as well as the high aspect ratio (height /radius ) of the cathode tip end.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.291-291
• /
• 2010

Electron-beam lithography (EBL) process is a versatile tool for a fabrication of nanostructures, nano-gap electrodes or molecular arrays and its application to nano-device. However, it is not appropriate for the fabrication of sub-5 nm features and high-aspect-ratio nanostructures due to the limitation of EBL resolution. In this study, the precision assembly and alignment of DNA molecule was demonstrated using sub-5 nm nanostructures formed by a combination of conventional electron-beam lithography (EBL) and plasma ashing processes. The ma-N2401 (EBL-negative tone resist) nanostructures were patterned by EBL process at a dose of $200\;{\mu}C/cm2$ with 25 kV and then were ashed by a chemical dry etcher at microwave (${\mu}W$) power of 50 W. We confirmed that this method was useful for sub-5 nm patterning of high-aspect-ratio nanostructures. In addition, we also utilized the surface-patterning technique to create the molecular pattern comprised 3-(aminopropyl) triethoxysilane (APS) as adhesion layer and octadecyltrichlorosilane (OTS) as passivation layer. DNA-templated gold nanoparticle chain was attached only on the sub-5 nm APS region defined by the amine groups, but not on surface of the OTS region. We were able to obtain DNA molecules aligned selectively on a SiO2/Si substrate using atomic force microscopy (AFM).