• The Journal of the Acoustical Society of Korea
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• v.10 no.3
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• pp.19-30
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• 1991

The surface properties such as energy gap, exciton, shallow trap level, deep trap level, type inversion with annealing and metastable state of $EL_2$ level of SI GaAs wafers and the conductivity distribution of 2 inch Cr doped GaAs wafer were investigated using nondestructive TAV(transverse acoustoelectric voltage) technique. The TAV is generated when SAW and semiconductor interact. We also have tried newly SAW oscillator technique to investigate the surface properties of semiconductor wafers and we have shown the validity of this technique.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.883-886
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• 2001

The mechanical properties such as the Young's modulus, damping ratio, vibration mode and hardness of the disk materials heat-treated under various conditions are measured, and the relations between there properties and the cutting characteristics such as early tip fracture are examined. The results obtained from this study are as follows. The circular saw with the V-Cr added disk has higher young's modulus and damping ratio than the saw with STC5 disk, preventing the early fracture of tungsten carbide due to the above properties. The circular saw with the disk which is subjected to the heat treatment at the quenching temperature of $830^{\circ}C$ and at the temperature of $550^{\circ}C$ have the best tool life and surface roughness.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04b
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• pp.13-16
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• 2009

In this study, AlN thin films were deposited on a polycrystalline (poly) 3C-SiC buffer layer for surface acoustic wave (SAW) applications using a pulsed reactive magnetron sputtering system. AFM, XRD and FT-IR were used to analyze structural properties and preferred orientation of the AlN/3C-SiC thin film. Suitability of the film in SAW applications was investigated by comparing the SAW characteristics of an interdigital transducer (IDT)/AlN/3C-SiC structure with the IDT/AIN/Si structure at 160 MHz in the temperature range $30-150^{\circ}C$. These experimental results showed that AlN films on the poly 3C-SiC layer were highly (002) oriented. Furthermore, the film showed improved temperature stability for the SAW device, $TCF\;=\;-18\;ppm//^{\circ}C$. The change in resonance frequency according to temperature was nearly linear. The insertion loss decrease was about $0.033dB/^{\circ}C$. However, some defects existed in the film, which caused a slight reduction in SAW velocity.

• Journal of Korean Society of Steel Construction
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• v.30 no.1
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• pp.13-23
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• 2018

The use of a built-up H-beam (BH) that can easily manufacture a section is increasing. This is a basic study on standardization of BH. It confirmed the material properties of SM490 and SM520 steel such as yield strength, tensile strength, elongation, charpy absorbed energy, and else. The six BH specimens were manufactured with single-SAW or tandem-SAW. The welding performance was confirmed by collecting the macroscopic specimen and T-bar tensile specimen form the BH. As a result of the material property test, the properties of SM490 and SM520 which are made in Korea both satisfied the KS. As a result of the welding performance experiment, it is determined that the weld zone of BH has sufficient welding performance. Therefore, they are determined that the SM490 and SM520 steel are a proper material of BH, and the single-SAW and the tandem-SAW show a sufficient welding performance.

• Korean Journal of Materials Research
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• v.12 no.7
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• pp.522-527
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• 2002

To investigate the SAW properties of GaN films on c-plane sapphire substrates, we carried out both the experimental measuring and theoretical calculation. The experimental characterization of SAW propagation properties was performed with a linear array of interdigital transducer (IDT) structures, while SAW velocities were calculated by matrix methods. HVPSAW mode with the propagation velocity over 10,000m/s and PSAW mode as well as GSAW could be observed in experimental determination. These results were verified by matching with the theoretical calculation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.71-72
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• 2008

In this paper, the effect of thermal annealing on surface acoustic wave (SAW) properties of aluminum nitride (AlN) films were described. The films were fabricated on Si substrates by using Pulsed Reactive Magnetron Sputtering System. The SAW properties of $600^{\circ}C$-annealed AlN films were better than those of both $900^{\circ}C$-annealed AlN films and as-deposited ones. Their SAW velocities (Raleigh mode) and insertion losses were about 5212 m/s and 16.19 dB at $600^{\circ}C$ with the wavelength of $40{\mu}m$. The dependence of characteristics of AlN films on annealing conditions were also evaluated by using Fourier Transform-Infrared Spectroscopy (FT-IR) Spectrums and Atomic Force Microscopy (AFM).

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.80-80
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• 2000

Surface acoustic wave (SAW) devices have become more important as mobile telecommunication systems need h호-frrequency, low-loss, and down-sized components. Higher-frequency SAW divices can be more sasily realized by developing new h호-SAW-velocity materials. The ZnO/diamond/Si multilasyer structure is one of the most promising material components for GHz-band SAW filters because of its SAW velocity above 10,000 m/sec. Silicon carbide is also a potential candidate material for high frequency, high power and radiation resistive electronic devices due to its superior mechanical, thermal and electronic properties. However, high price of commercialized 6- or 4H-SiC single crystalline wafer is an obstacle to apply SiC to high frequency SAW devices. In this study, single crystalline 3C-SiC thin films were grown on Si (100) by MOCVD using bis-trimethylsilymethane (BTMSM, C7H20Si7) organosilicon precursor. The 3C-SiC film properties were investigated using SEM, TEM, and high resolution XRD. The FWHM of 3C-SiC (200) peak was obtained 0.37 degree. To investigate the SAW propagation characteristics of the 3C-SiC films, SAW filters were fabricated using interdigital transducer electrodes on the top of ZnO/3C-SiC/Si(100), which were used to excite surface acoustic waves. SAW velocities were calculated from the frequency-response measurements of SAW filters. A generalized SAW mode. The hard 3C-SiC thin films stiffened Si substrate so that the velocities of fundamental and the 1st mode increased up to 5,100 m/s and 9,140 m/s, respectively.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.8
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• pp.319-324
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• 2003

AIN thin films are deposited on Si (100) and $SiO_2$/Si substrates by using an RF magnetron sputtering method and by changing the conditions of deposition variables, such as RF power, $N_2$/Ar flow ratio, and substrate temperature ($T_sub$). For all the deposited AIN films, XRD Peak patterns are monitored to examine the effect of deposition condition on the crystal orientation. Highly (002)-oriented AIN films are obtained at following nominal deposition conditions; RF Power : 350W, $N_2$/Ar ratio = 10/20, T$_{sub}$ : $250^{\circ}C$, and working pressure = 5mTorr, respectively. AIN-based SAW devices are fabricated using a lift-off method by varying the thickness of AIN layer. Insertion losses and side-lobe rejection levels of fabricated SAW devices are extracted from their frequency response characteristics, which are also compared in terms of AIN thickness and substrate. Relationships between the film properties of AIN films and the frequency responses of SAW devices are discussed. It is concluded from the experimental results that the (002)-preferred orientation as well as the surface roughness of AIN film may play a crucial role of determining the device performances of AIN-SAW devices.s.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.235-235
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• 2009

This paper describes the influence of a polycrystalline (poly) 3C-SiC buffer layer on the surface acoustic wave (SAW) properties of poly aluminum nitride (AlN) thin films by comparing the center frequency, insertion loss, the electromechanical coupling coefficient ($k^2$), andthetemperaturecoefficientoffrequency(TCF) of an IDT/AlN/3C-SiC structure with those of an IDT/AlN/Si structure, The poly-AlN thin films with an (0002)-preferred orientation were deposited on a silicon (Si) substrate using a pulsed reactive magnetron sputtering system. Results show that the insertion loss (21.92 dB) and TCF (-18 ppm/$^{\circ}C$) of the IDT/AlN/3C-SiC structure were improved by a closely matched coefficient of thermal expansion (CTE) and small lattice mismatch (1 %) between the AlN and 3C-SiC. However, a drawback is that the $k^2(0.79%)$ and SAW velocity(5020m/s) of the AlN/3C-SiC SAW device were reduced by appearing in some non-(0002)AlN planes such as the (10 $\bar{1}$ 2) and (10 $\bar{1}$ 3) AlN planes in the AlN/SiC film. Although disadvantages were shown to exist, the use of the AlN/3C-SiC structure for SAW applications at high temperatures is possible. The characteristics of the AlN thin films were also evaluated using FT-IR spectra, XRD, and AFM images.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.147-149
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• 2005

Effect of nitrogen content on SAW weld metal properties were investigated. Weld metal nitrogen content increased with an increase of base metal nitrogen content due to dilution. High nitrogen content in weld metal resulted in high free nitrogen content, and consequently reduced impact toughness due to, mainly, strain aging effect.