• Korean Journal of Materials Research
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• v.5 no.6
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• pp.650-656
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• 1995

High frequency SAW filters for cellular communications were fabricated by metallizing 36$^{\circ}$Y-X LiTaO$_3$piezoelectric substrate with IIDT type electrodes. It was found that the center frequency of the filter was lowered than as designed. In order to overcome such a drawback and enable a fine tuning of its center frequency, dielectric SiN$_{x}$ thin films were deposited on LiTaO$_3$substrate by PECVD as passivation layer and then frequency responses were also characterized. As a result, the center frequency of the filter could be shifted to a higher frequency with increasing the thickness of SiN$_{x}$ film, because SAW velocity increased with increasing the ratio of the thickness of dielectric thin film to wavelength. The insertion loss of the filter, however, became larger with increasing the thickness of SiN$_{x}$ film.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.114-114
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• 2012

Even though graphene was introduced with a great hope to replace silicon in future, small (or zero) band gap and poor stability have become major challenges in graphene electronics. Especially, rectification and amplification function which are the elemental functions of silicon device, is very difficult to implement without a bandgap. However, the graphene can still be used in many other device applications if the merits of graphene are creatively utilized. For example, graphene can be applied to almost any kind of substrate. Its conductivity can be varied in some degree using electric field, charge dipole, attached molecules, and many other ways. Recently, graphene stacked with ferroelectric materials or piezoelectric materials has been actively studied for various device applications. In this talk, various device applications of graphene using hybrid stack or novel device structure will be introduced and their prospect will be discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.146-146
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• 2016

Zinc Oxide (ZnO) was known as a promising material for surface acoustic wave devices, gas sensors, optical devices and solar cells due to piezoelectric material, large band gap of 3.37 eV and large exciton binding energy of 60 meV at room temperature. In particular, the alignment of ZnO nanostructures into ordered nanoarrays can bring about improved sensitivity of devices due to widen the surface area to catch a lot of gas particle. Oxygen plasma treatment is used to specify the nucleation site of round patterned ZnO nanorods growth. Therefore ZnO nanorods were grown on a quartz substrate with patterned polystyrene monolayer by hydrothermal method after oxygen plasma treatment. And then, we carried out nanostructures by adjusting the diameter of the arranged ZnO nanorods according to polystyrene spheres of various sizes. The obtained ZnO nanostructures was characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM).

• Journal of Ocean Engineering and Technology
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• v.29 no.1
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• pp.94-99
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• 2015

Lead zirconate titanate (PZT) thick films with thicknesses of ㎛ were fabricated on silicon substrates using an aerosol deposition method. A PZT powder solution was prepared using a sol-gel process. The average diameters (d50) obtained were 1.67, 1.98, and 2.40μm when the pyrolysis temperatures were 300℃, 350℃, and 450℃ respectively. The as-deposited film had a uniform microstructure without any cracks or pores. The as-deposited films on silicon were annealed at a temperature of 700℃. The 20-㎛-thick PZT film showed good adherence between the PZT film and substrate, with no tearing observed in the conventional solid phase process. This was probably because the presence of pores produced from organic residue during annealing relieved the residual stresses in the deposited film.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1545_1546
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• 2009

This paper reports a novel wireless love-wave biosensor on $41^{\circ}$ YX $LiNbO_3$ piezoelectric substrate and $SiO_2$ guiding layer for Immunoglobulin G (IgG) detection by protein binding. Different from the traditional biosensors based on surface acoustic wave (SAW) oscillator structured by delay line/resonators, a 440MHz reflective delay line consists of SPUDTs and three reflectors placed on $41^{\circ}$ YX $LiNbO_3$ in a row was fabricated as the sensor element. Good linearity, reproducibility, and high sensitivity were observed in the IgG concentration range 1~65nM. Unique advantages as high sensitivity, passive and simple measurement system are present over currently available other biosensors.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.915-920
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• 2007

AIN-based film bulk acoustic resonator (FBAR) devices which adopt a membrane-type configuration such as Mo/AIN/bottom-metal/Si are fabricated by employing a novel process. The proposed resonator structure does not require any supporting layer above the substrate, which leads to the reduction in energy loss of the resonators. For all the FBAR devices, the frequency response characteristics are measured and the device parameters, such as return loss and input impedance, are extracted from the frequency responses, and analyzed in terms of the various metals such as Al. Cu, Mo, W used in the bottom-electrode. The mass-loading effect caused by the used bottom-electrode metals is found to be the main reason for the difference revealed in the measured characteristics of the fabricated FBAH devices. The results obtained in this study also show that the degree of match in lattice constant and thermal expansion coefficient hetween piezoelectric layers and electrode metals is crucial to determine the device performance of FEAR.

• Journal of the Korean Vacuum Society
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• v.8 no.4A
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• pp.425-431
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• 1999

$Pb(Zr_{0.52}, Ti_{0.48})O_3$ (PZT) thick films as an actuating material with conducting oxides, $(La_{0.5}Sr_{0.5}) CoO_3$ (LSCO), have been fabricated by sol-gel method for Optical Micro-Electro-Mechanical System (MEMS) devices, in which PZT/LSCO/SiO2 structures were used. In order to improve the adhesion to LSCO solution in order to enhance the wetting behavior of a water-based LSCO precursor solution and further to improve the adhesion between LSCO and $SiO_2$ layers. PZT films were made using 1-3 propanediol based precursor solution which has a high viscosity and a boiling point appropriate for thick film fabrication. In the precursor solution, Ti-propoxied and Zr-propoxied are partially substituted with acetylacetone to achieve the solution stability while maintaining reactivity. Crack free PZT films (0.8~1$\mu\textrm{m}$) have been successfully fabricated at crystallization temperatures above $700^{\circ}C$. Dielectric constants and dielectric losses of the PZT films were 900~1200and 2~5%, respectively. Piezoelectric constant $d_{33}$ of the PZT films constrained by a substrate were 200pm/V at 100kV/cm.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.12
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• pp.1107-1113
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• 2014

In this article, the megasonic cleaning system for cleaning micro/nano particles from flat panel display (FPD) surfaces was developed. A piezoelectric actuator and a waveguide were designed by finite element method (FEM) analysis. The calculated peak frequency value of the quartz waveguide was 1002 kHz, which agreed well with the measured value of 1003 kHz. The average acoustic pressure of the megasonic cleaning system was 43.1 kPa, which is three times greater than that of the conventional type of 13.9 kPa. Particle removal efficiency (PRE) tests were performed, and the cleaning efficiency of the developed system was proven to be 99%. The power consumption of the developed system was 64% lower than that of the commercial system. These results show that the developed megasonic cleaning system can be an effective solution in particle removing from FPD substrate with higher energy efficiency and lower chemical and ultra pure water (UPW) consumption.

• JSTS:Journal of Semiconductor Technology and Science
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• v.6 no.2
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• pp.90-94
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• 2006

We report on the growth and characterization of InGaN/GaN MQWs on two different types of sapphire substrates and GaN substrates. The InGaN/GaN MQWs are grown by using metalorganic chemical vapor deposition. Our analysis of the satellite peaks in the HRXRD patterns shows, GaN substrates InGaN/GaN MQW compared to sapphire substrates InGaN/GaN MQW, more compressive strain on GaN substrates than on sapphire substrates. However, results of optical investigation of InGaN/GaN MQWs grown on GaN substrates and on sapphire substrates, which have lower Stokes-like shift of PL to GaN substrates compared to sapphire substrates, are shown to the potential fluctuation and the quantum-confined Stark effect induced by the built-in internal field due to spontaneous and straininduced piezoelectric polarizations. The InGaN/GaN MQWs are shown to quantify the Stokes-like shift as a function of x.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.12
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• pp.1730-1736
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• 2013

Slanted and chirp interdigital transducer(IDT) configurations were studied for generating the surface acoustic wave(SAW) with wide bandwidths on a piezoelectric substrate. These devices can be applied to manipulate optical path of light along the waveguide, ultimately used for optical switches and holographic image implementation. Prior to fabrication, the coupling of modes(COM) modeling and simulation were performed to extract optimal design parameters. The optimally designed wideband device showed wide bandwidth of 30MHz, low insertion loss of -25dB, and abrupt side suppression ratio (SSR). Several design conditions were determined during device implementation, such as slanted angle, aperture length, number of fingers, and central frequencies of IDTs. These factors were experimentally analyzed and described in details in this paper.