• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.2
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• pp.96-110
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• 1995

Traveling-wave electrodes for the high-speed Ti:LiNbO$_{3}$ modulators are designed. For a solution to the problems of 1) phase-velocity mismatching between the optical wave and the Modulating M/W, 2) M/W electrode characteristic impedance mismateching, we assume devices with 1$\mu$m thick SiO$_{2}$ buffer layer between the electrode and the Ti:LiNbO$_{3}$ substrate. The electrode analyses are performed by the FEM using the second-order triangular elements. The optimum design parameters to satisfy the phase-velocity matching and the characteristic impedance matching are sought for. By use of the analyses' results, a Mach-Zehnder optical modulator with a CPW electrode is designed as an example. the band-width estimation is also illustrated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.15-15
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• 2008

산화물 반도체가 실리콘 기반의 기술을 대체할 새로운 기술로써 주목을 받기 시작하면서, 산화아연을 이용한 박막트랜지스터가 많은 주목을 받고 있다. 여기에 기존의 $SiO_2$를 대체할 새로운 High-k Material에 대한 연구 또한 진행되고 있는데, 이들의 가장 큰 문제점중 하나는 Interface Charge Trap이며, 그에 따른 결과로 히스테리시스 특성이 나타나게 되고, 이는 소자의 신뢰성에 큰 걸림돌이 되고 있다. 이번 연구에서는, High-k Material들 중의 하나인, $HfO_2$를 게이트 절연막으로 사용함에 있어서 Interface Charge Trap이 발생하는 문제를 해결하고자 하며, Low-k Material중에서 비교적 높은 유전상수를 갖는 $Al_2O_3$를 Buffer Layer로써 사용하여, 히스테리시스 특성을 향상 시켰다.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.634-638
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• 2003

We reported the a-Si crystallization using a XeCl excimer laser annealing on the plastic substrate. The poly-Si film is able to grow in the low temperature and light substrate like a plastic. For the preparation of sample, substrate is cleaned by organic liquids. The film of $CeO_{2}$ layer as the buffer layer was grown by sputtering methods. After a-Si film deposition using ICPCVD, the film was crystallized by XeCl excimer laser. In this paper, we present the crystallization properties of a-Si on the plastic substrate

• Korean Journal of Materials Research
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• v.8 no.12
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• pp.1170-1175
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• 1998

PZT films without lower electrode were deposited on the highly doped Si(100) substrate with MgO buffer layer (Mgo/si) by RF magnetron sputtering method followed by the rapid thermal annealing at $650^{\circ}C$ . We investigated the dependences of the crystalline and electrical properties on the MgO thickness and the RTA post annealing. The PZT films on bare Si (without MgO) showed pyrochlore crystal structure while those on MgO(50 )/Si substrates showed the typical perovskite crystal structures. From SEM and AES analysis, the thickness of PZT films was about 7000 showing relatively smooth interface. The depth profiles indicated that atomic species were distributed homogeneously in the PZT/MgO/Si substrate. The dielectric constant($\varepsilon_{r}$ ) and remanent polarization(2Pr) were about 300 and $14\mu$C/$\textrm{cm}^2$;, respectively. The leakage current was about $3.2\mu$/A$\textrm{cm}^2$.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.128.1-128.1
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• 2016

Nitrided-metal gates on the high-${\kappa}$ dielectric material are widely studied because of their use for sub-20nm semiconductor devices and the academic interest for the evanescent states at the Si/insulator interface. Issues in these systems with the Si substrate are the electron mobility degradation and the reliability problems caused from N defects that permeates between the Si and the $SiO_2$ buffer layer interface from the nitrided-gate during the gate deposition process. Previous studies proposed the N defect structures with the gap states at the Si band gap region. However, recent experimental data shows the possibility of the most stable structure without any N defect state between the bulk Si valence band maximum (VBM) and conduction band minimum (CBM). In this talk, we present a new type of the N defect structure and the electronic structure of the proposed structure by using the first-principles calculation. We find that the pair structure of N atoms at the $Si/SiO_2$ interface has the lowest energy among the structures considered. In the electronic structure, the N pair changes the eigenvalue of the silicon-induced gap state (SIGS) that is spatially localized at the interface and energetically located just above the bulk VBM. With increase of the number of N defects, the SIGS gradually disappears in the bulk Si gap region, as a result, the system gap is increased by the N defect. We find that the SIGS shift with the N defect mainly originates from the change of the kinetic energy part of the eigenstate by the reduction of the SIGS modulation for the incorporated N defect.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.6
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• pp.61-70
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• 1999

An optical switch composed of three-identical, equally-spaced $Ti:LinbO_3$ waveguides and overlaid Al electrodes of CPW structure was designed and fabricated. Patterned Ti was diffused into z-cut $LinbO_3$ substrates at $1025^{\circ}C$ for 6 hours to make a three-waveguide directional coupler. $SiO_2$ buffer layer of $1.2{\mu}m$ was grown by the PECVD to reduce the propagation loss of TM mode, and Al electrodes were built on the layer for switching the guided beam. For an incident beam of ${\lambda}=1.3{\mu}m$, almost perfect optical coupling between two outer waveguides was observed. When an electric field was applied to detune the three waveguides anti-symmetrically, the optical switching phenomenon was successfully confirmed.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1521-1528
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• 1994

To improve mechanical strength of bioglass, it is considered to use the glass as a coating material to alumina, but the difference in thermal expansion coefficient between two materials is too high to make a good coating. The aim of the present study, therefore, is to find out proper glass composition matching its thermal expansion coefficient to that of alumina without losing biocompatibility. In the present work, various glasses were prepared by substituting B2O3 and CaO for Na2O in the glass system of 55.1%SiO2-2.6%P2O5-20.1%Na2O-13.3%CaO-8.9%CaF2 (in mole%), and the thermal expansion property and reaction property in tris-buffer solution for the resulting glasses were measured. The thermal expansion coefficient of the glass was decreased with the substitution of B2O3 for Na2O, and it became close to that of alumina in the glass in which 8 mole% of CaO was substituted for Na2O. Hydroxyapatite formation was enhanced and silica rich layer thickness was decreased with B2O3 substitution for Na2O. CaO substitution for Na2O didn't deteriorated the hydroxyapatite development.

• Current Optics and Photonics
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• v.5 no.1
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• pp.1-7
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• 2021

For higher sensitivity in ultraviolet (UV) and even vacuum ultraviolet (VUV) detection of silicon-based sensors, a sandwich-structured film sensor based on Ag Localized Surface Plasmon Resonance (LSPR) was designed and fabricated. This film sensor was composed of a Ag nanoparticles (NPs) layer, SiO2 buffer and fluorescence layer by physical vapour deposition and thermal annealing. By tuning the annealing temperature and adding the SiO2 layer, the resonance absorption wavelength of Ag NPs matched with the emission wavelength of the fluorescence layer. Due to the strong plasmon resonance coupling and electromagnetic field formed on the surface of Ag NPs, the radiative recombination rate of the luminescent materials and the number of fluorescent molecules in the excited state increased. Therefore, the fluorescent emission intensity of the sandwich-structured film sensor was 1.10-1.58 times at 120-200 nm and 2.17-2.93 times at 240-360 nm that of the single-layer film sensor. A feasible method is provided for improving the detection performance of UV and VUV detectors.

• Journal of the Korean Ceramic Society
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• v.43 no.6 s.289
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• pp.362-368
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• 2006

Epitaxial $Ba_{0.5}Sr_{0.5}TiO_3$ (BSTO) thin films have been grown on TiN buffered Si (001) substrates by Pulsed Laser Deposition (PLD) method and the effects of substrate temperature and oxygen partial pressure during the deposition on their dielectric properties and crystallinity were investigated. The crystal orientation, epitaxy nature, and microstructure of oxide thin films were investigated using X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Thin films were prepared with laser fluence of $4.2\;J/cm^2\;and\;3\;J/cm^2$, repetition rate of 8 Hz and 10 Hz, substrate temperatures of $700^{\circ}C$ and ranging from $350^{\circ}C\;to\;700^{\circ}C$ for TiN and oxide respectively. BSTO thin-films were grown on TiN-buffered Si substrates at various oxygen partial pressure ranging from $1{\times}10^{-4}$ torr to $1{\times}10^{-5}$ torr. The TiN buffer layer and BSTO thin films were grown with cube-on-cube epitaxial orientation relationship of $[110](001)_{BSTO}{\parallel}[110](001)_{TiN}{\parallel}[110](001)_{Si}$. The crystallinity of BSTO thin films was improved with increasing substrate temperature. C-axis lattice parameters of BSTO thin films, calculated from XRD ${\theta}-2{\theta}$ scans, decreased from 0.408 m to 0.404 nm and the dielectric constants of BSTO epitaxial thin films increased from 440 to 938 with increasing processing oxygen partial pressure.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.3
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• pp.85-91
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• 1999

$H:LiNbO_3$ optical modulator with Cu/parylene electrode layer, which has a merits in the bandwidth, power consumption and fabrication conditions as compared with conventional Au/Cr/$SiO_2$, is proposed and fabricated. Analysis and design of optical modulator is performed by finite element calculation. Various unit processes for fabricating the proposed modulator, 1550nm $H:LiNbO_3$ optical waveguide, parylene buffer layer, and CPW Cu electrode, were developed, After dicing and end-face polishing of fabricated modulator chip, optical modulation responses as sawtooth electrical driving voltage has been measured at low frequencies. Properties of optical waveguide had not been changed before and after Cu/parylene electrode processes, which make confirm the reproducible fabrication of optical modulator.