• The Journal of the Acoustical Society of Korea
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• v.19 no.2
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• pp.33-39
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• 2000

We have studied to obtain the frequency characteristics of the Surface Acoustic Wave(SAW) bandpass filter, having low shape factor, it's interdigital transducer(IDT) was formed on the 35° Y-cut X-propagation Quartz substrate and was evaporated by Aluminium. And then, we performed computer-simulation by a simulator. And, we can design that the apodization weighted type IDT as an input transducer of the filter and the withdrawal weighted type IDT as an output transducer of the filter from the results of our computer-simulation. Also, we have employed that the number of pairs of the input and output IDT are 2200 pairs and 1000pairs, respectively and used the Kaiser-Bessel window function in order to minimize the effect of ripple. And, while the width and the space of IDT's finger are 6㎛ m and 5.75㎛, respectively and we could obtain the resonable results when the IDT thickness was 6000Å in consideration of the ratio of SAW's wavelength, and IDT aperture is 2mm. Frequency response of the fabricated SAW bandpass filter has the property that the center frequency is about 70MHz, shape factor is less than 1.3, bandwidth at the 1.5dB is probably 1.3MHz, out-band attenuation is almost -45dB, insertion loss is 19dB and ripple in the width of bandpass is 1dB approximately. Therefore, these frequency characteristics of the fabricated SAW bandpass filter are agreed well with the designed values.

• Journal of the Korean Vacuum Society
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• v.15 no.4
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• pp.404-409
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• 2006

Thin-film $ZnGa_2O_4 : Mn^{2+}$ phosphors of spinel structure were grown on quartz substrate by RF magnetron sputtering method at room temperature. As an increase of post-annealing temperatures, crystallinity, surface roughness and stoichiometry of thin films were varied. At the post-annealing temperatures of $500^{\circ}C$ and $600^{\circ}C$, the luminescence intensity was poor due to the poor crystallinity. The smallest surface roughness was observed at the sample post-annealed at $700^{\circ}C$ leading to low external extraction efficiency, and poor luminescence intensity. The highest luminescence intensity was shown at the sample post-annealed at $800^{\circ}C$. It was because both the surface roughness and crystallnity were optimized. On the other hand, at $900^{\circ}C$, the luminescence intensity was poor due to the violation of stoichiometry.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.3
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• pp.341-350
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• 1996

The CdS thin films are grown on quartz plate by hot wall epitaxy. The source and substrate temperature is $590^{\circ}C$ and $400^{\circ}C$ respectively, and thickness of the film is $2.5\;\mu\textrm{m}$. Using extrapolation method of X-ray diffraction patterns for the CdS thin film, it was found hexagonal structure whose lattice constant a and c were $4.137\;{\AA}$ and $6.713\;{\AA}$, respectively. Hall effect on this sample was measured by the method of van der Pauw and studied on cattirer density and mobility depending on temperature. From hall data, the mobility was likely to be decreased by piezoelectric scattering in the temperature range 30 K to 200 K and by polar optical scattering in the temperature range 200 K to 293 K. In order to explore the applicability as a photoconductive cell we measured the sensitivity ($\gamma$), the ratio of photocurrent to darkcurrent (pc/dc), maximum allowable power dissipation (MAPD), spectral response and response time. The results indicated that for the samples annealed in Cu vapor the photoconductive characteristics are the best. Then we obtained the sensitivity of 0.99, the value of pc/dc of $9.42{\times}10^{6}$, the MAPD of 318 mW, and the rise and decay time of 10 ms and 9 ms, respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.5
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• pp.1-7
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• 2007

AZO thin films have been fabricated on quartz substrate with various Al doping concentrations and annealing temperatures by sol-gel method. The bset condition of (002) orientation and smooth surface (rms = 1.082 nm) is obtained for the AZO thin film doped with 1 mol % Al and annealed at 550 $^{\circ}C$. The optical transmittance of AZO thin films is higher than 80 % in the visible region. We observe that the energy band gap extends with increasing the Al doping concentration. This phenomenon is due to the Burstein-Moss effect. Through the measurement of Hall effect, it is observed that the AZO thin film has larger carrier concentration and smaller electrical resistivity than the pure ZnO thin film. However, the AZO thin film shows the decrease of carrier concentration and the increase of resistivity with the increase of Al concentration, that is due to the segregation of Al at grain boundaries. The maximum carrier concentration of $1.80{\times}10^{19}\;cm^{-3}$ and the minimum resistivity of 0.84 ${\Omega}cm$ are obtained for the AZO thin film doped with 1 mol % Al and annealed at 550 $^{\circ}C$.

• Korean Journal of Heritage: History & Science
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• v.45 no.1
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• pp.86-101
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• 2012

The constituting rocks of Multi-storied Round shape stone Pagoda of Unjusa Temple are lithic tuff and rhyolite tuff breaccia which show green or grey and also rock fragment with poor roundness are present in the structure. lithic tuff is composed of feldspar and quartz which are glassy texture and cryptocrystalline and also micro crystalline are scattered. phenocryst quartz and feldspar in the substrate composed of feldspar and opaque minerals are found in rhyolite tuff breaccia. dust, exfoliation, cavity, fracture and crack are observed in all the stone of the pagoda and the result of Infrared Thermography shows partial inter cavities have developed severely which may cause further exfoliation. In addition, a great deal of various grey, green, and yellow brown lichen as well as bryophyte are present at the upper part of eastern and western roof stone located above the third floor. Discolors remarkably shown at stereobate and roof stone are identified as inorganic pollutants such as manganese oxide, iron oxide and iron hydroxide. The stone of the pagoda of the Chemical Index of Alteration (CIA) and the Weathering Potential Index (WPI) are 55.69 and 1.12 respectively and this corresponds to a highly weathered stage. The measured values, average ultrasonic velocity 2,892m/s, coefficient of weathering 0.4k and compressive strength $1,096kg/cm^3$, suggest that the rock strength and durability are weakened.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.393-393
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• 2012

Optically active nanostructures such as subwavelength moth-eye antireflective structures or surface enhanced Raman spectroscopy (SERS) active structures have been demonstrated to provide the effective suppression of unwanted reflections as in subwavelength structure (SWS) or effective enhancement of selective signals as in SERS. While various nanopatterning techniques such as photolithography, electron-beam lithography, wafer level nanoimprinting lithography, and interference lithography can be employed to fabricate these nanostructures, roll-to-roll (R2R) nanoimprinting is gaining interests due to its low cost, continuous, and scalable process. R2R nanoimprinting requires a master to produce a stamp that can be wrapped around a quartz roller for repeated nanoimprinting process. Among many possibilities, two different types of mask can be employed to fabricate optically active nanostructures. One is self-assembled Au nanoparticles on Si substrate by depositing Au film with sputtering followed by annealing process. The other is monolayer silica particles dissolved in ethanol spread on the wafer by spin-coating method. The process is optimized by considering the density of Au and silica nano particles, depth and shape of the patterns. The depth of the pattern can be controlled with dry etch process using reactive ion etching (RIE) with the mixture of SF6 and CHF3. The resultant nanostructures are characterized for their reflectance using UV-Vis-NIR spectrophotometer (Agilent technology, Cary 5000) and for surface morphology using scanning electron microscope (SEM, JEOL JSM-7100F). Once optimized, these optically active nanostructures can be used to replicate with roll-to-roll process or soft lithography for various applications including displays, solar cells, and biosensors.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.5 s.96
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• pp.488-493
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• 2005

In this study, waveguide-to-CPW transitions were developed for integrating waveguide and MMIC at V-band. The finite element method for numerical analysis and repeated experiments were performed to propose two types of waveguide-to-CPW transition. Using quartz substrate, proposed structures were designed for low loss as well as broadband characteristics. These waveguide-to-CPW transitions showed a good reliability and insensitivity to matching precision, and they could be fabricated with lower cost than that of the conventional connectors. Proposed two types of the structure showed insertion loss less than 1.9 dB and return loss better than 14 dB from 53 GHz to 60 GHz except unwanted resonance region, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.8
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• pp.737-743
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• 2004

A fixed-tuned SIS(Superconductor-Insulator-Superconductor) mixer across 120∼180 GHz band has been developed. This mixer employs an SIS chip fabricated by Nobeyama radio observatory which consists of a series array of 6 Nb/Al-Al$_2$O$_3$/Nb junctions in a microstrip line on a fused quartz substrate. The SIS chip is placed at the center of the half-height waveguide mixer mount to have a good incoming signal coupling over the whole frequency band. No mechanical tuner was used in the SIS mixer and the RF signal and local oscillator power are injected to the mixer via a cooled cross-guide coupler. In order to prevent the IF signal loss, the If output impedance of the SIS mixer was matched to the 50 $\Omega$ input impedance of the IF chain. Measured double sideband noise temperatures of a receiver using the SIS mixer are 32∼131 K over 120∼180 GHz band. The developed SIS mixer is now in use for radio astronomical observations on the TRAO 14 m radio telescope.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.5
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• pp.325-330
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• 2017

We fabricated 1-D and 2-D diffraction gratings of SiOx anti-reflection (AR) film grown on a quartz substrate and integrated them into a c-Si photovoltaic (PV) submodule. The light-trapping effect of the resulting submodules was studied in terms of the oblique optical incident angle, ${\theta}_i$. As the ${\theta}_i$ increased, solar conversion efficiency, ${\eta}$, was improved as expected by the increased optical transmission caused by the grating. For ${\theta}_i{\leq}30^{\circ}$, the relative solar conversion efficiency, ${\Delta}{\eta}$, of a 1-D SiOx (t=300 nm) grating, compared to that of a flat SiOx AR-coated integrated PV submodule, was improved very little, with a small variation of within 2%, but increased markedly for ${\theta}_i{\geq}40^{\circ}$. We observed a change of ${\Delta}{\eta}$ as large as 10.7% and 9.5% for the SiOx grating of period t=800 nm and 1200 nm, respectively. For a 2-D SiOx (t=300 nm) grating integrated PV submodule, however, the optical trapping behavior was similar in terms of ${\theta}_i$ but its variation was small, within ${\pm}1.0%$.

• Korean Journal of Optics and Photonics
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• v.21 no.4
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• pp.175-178
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• 2010

A transmission type color filter based on a thin film Ag-$SiO_2$-Ag etalon was proposed and realized in a quartz substrate. The device could acquire infrared suppressed transmission and wide effective area compared to costly e-beam lithography and laser interference lithography. The FDTD method was introduced to take into account the effect of the dispersion characteristics of the silver metal and the thickness thereof. Three different color filters were devised: The cavity length for the red, green and blue filters were 160 nm, 130 nm, and 100 nm respectively, with the metal layer unchanged at 25 nm. The observed center wavelengths were measured at 650 nm, 555 nm, and 480 nm for the red, green, and blue devices; the corresponding bandwidths were about 120 nm, 100 nm, and 120 nm; and the peak transmission for all was ~60%. Finally the relative transmission was measured to decline with the angle of the incident beam with the rate of 1%/degree.