• Journal of Ocean Engineering and Technology
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• v.15 no.1
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• pp.57-66
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• 2001

In order to measure steel corrosion in mortar by a transient electro-magnetic (TEM) Method, the development of the sensors have been studied. The sensors were made of enamelled wire with diameter of 0.25mm and Acril. The sensor configuration was used as a coincident loop type. The secondary electro motive force(EMF) was measured with SIROTEM III. The accelerator was equipped with the SIROTEM III. The accelerator permits the transmitter to turn off approximately 10~15 times faster than normal. The high resolution time series used for very shallow or high resistivity investigation was selected. The steels were embedded in mortar which were made from sand : cement : water ratio of 2 : 1: 0.5. The mortar specimen was 50cm long, 20cm wide and 10cm thick. To investigate steel corrosion in mortar, the sensors used were with 2$\times$2$cm^2$(3, 6, 9$\Omega$), 3$\times$3$cm^2$(3, 6, 9$\Omega$) and 6$\times$6$cm^2$(3, 6, 9$\Omega$). The obtained result obtained showed that the sensor 8(6$\times$6$cm^2$, 6$\Omega$) was the proper sensor for the measurement of steel corrosion in mortar.

• Applied Microscopy
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• v.45 no.4
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• pp.195-198
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• 2015

Gas-assisted etching (GAE) with focused ion beam (FIB) was applied to prepare plan-view specimens of Cu thin-layer on a silicon substrate for transmission electron microscopy (TEM). GAE using $XeF_2$ gas selectively etched the silicon substrate without volume loss of the Cu thin-layer. The plan-view specimen of the Cu thin film prepared by FIB milling with GAE was observed by scanning electron microscopy and $C_S$-corrected high-resolution TEM to estimate the size and microstructure of the TEM specimen. The GAE with FIB technique overcame various artifacts of conventional FIB milling technique such as bending, shrinking and non-uniform thickness of the TEM specimens. The Cu thin film was uniform in thickness and relatively larger in size despite of the thickness of <200 nm.

• Applied Microscopy
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• v.29 no.4
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• pp.493-498
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• 1999

With increasing demand for fast and reliable, yet economical data storage devices, the role of optical disk technology is becoming more important. In recent years, advanced laser technology combined with new materials has given the competitive edge over the traditional magnetic memory devices both in memory capacity and reliability of data retrieval. Continuing effort is being put into developing smaller and more complex structures for optical disks to increase their memory density. Characterization of such multilayered structure requires not only high spatial resolution for observation but also laborious specimen preparation. In this paper, the method of preparing optical disk specimens for TEM characterization is described in detail. The microstructural features in optical disks observed by TEM are also discussed.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.09a
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• pp.11-18
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• 2005

Filament inversion routines are highly effective for target definition whenever total-field DHTEM vectors can be obtained using three-component logging tools. However most cross-hole components contain significant noise related to sensor design and errors in observation of probe rotation. Standard stacking methods can be used to improve data quality but additional statistical methods based on cross-correlation and spatial averaging of orthogonal components may be required to ensure a consistent vector migration path. Apart from assisting with spatial averaging, multiple filaments generated for successive time-windows can provide additional imaging information relating to target geometry and current migration. New digital receiver systems provide additional time-windows to provide better tracking options necessary for high-resolution imaging of this type.

• Bulletin of the Korean Chemical Society
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• v.28 no.3
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• pp.391-396
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• 2007

The three-dimensional structure of an inorganic crystal, CaMoO4 (space group I 41/a, a = 5.198(69) A and c = 11.458(41) A), was determined by electron crystallography utilizing a high voltage electron microscope. An initial structure of CaMoO4 was determined with 3-D electron diffraction patterns. This structure was refined by crystallographic image processing of high resolution TEM images. X-ray crystallography of the same material was performed to evaluate the accuracy of the TEM structure determination. The cell parameters of CaMoO4 determined by electron crystallography coincide with the X-ray crystallography result to within 0.033-0.040 A, while the atomic coordinates were determined to within 0.072 A.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.10
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• pp.930-934
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• 2006

This paper reports a change of carbon nanotubes(CNTs) properties by post-treatment process after growth of CNTs. CNTs were treated by thermal method and solution method, and then investigated in detail using field emission scanning electron microscopy(FE-SEM), high resolution transmission scanning electron microscopy(HR-TEM), RAMAN spectroscopy, and Fourier Transform Infrared Spectrometer (FT-IR). FT-IR spectra showed that the amount of hydroxyl generated on surface of CNTs were changed with post-treatment condition. FE-SEM and TEM images were shown CNTs diameter and density variations were dependent with their treatment conditions. RAMAN spectroscopy was shown that carbon nanotubes structure vary with treatment conditions.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.121-121
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• 1999

Gallium nitride (GaN) semiconductor is intensively under investigation for commercialization of short wavelength light emitting devices and laser diodes. One of serious obstacles to overcome is to reduce the defect density in GaN film grown by various techniques such as MOCVD, HVPE, etc. Many research groups including SAIT are trying to improve the defect density to 106-107/cm2 from the level of 108-1010/cm2. We have investigated epitaxial growth behaviour of GaN thin and thick films under hidride vapour phase epitaxy (HVPE) condition. In this report, we present the microstructural and crystallographical characteristics of the GaN films grown on sapphire (0001) substrate which were studied by both conventional and high-resolution transmission electron microscopy (TEM). Also we present some microscopic analysis results obtained from GaN films grown by ELO(dpitzsial lateral overgrowth)-HVPE and from GaN quantum well structures grown by MOCVD. Another serious problem in growing GaN thick film by HVPE is internal micro-cracks. We also comment the origin of the micro-crack.

• Applied Microscopy
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• v.26 no.4
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• pp.479-487
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• 1996

Thin epilayer structures of GaAs/AlAs/InGaAs, grown by Molecular Beam Epitaxy, were investigated by high resolution transmission electron microscopy, Image in the [110] zone axis was taken and compared with the calculated images. The supercell structure which contains GaAs, AlAs and InGaAs layers was designed and was employed in the image calculation with MacTempas computer program. Good agreement was shown between experimental image and a set of calculated images with varying defocus and sample thickness.

• Journal of the Mineralogical Society of Korea
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• v.29 no.2
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• pp.73-78
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• 2016

The oxidation states of structural Fe in clay minerals often reflect the paleo-redox conditions of the depositional environments. It is inevitable to utilize the high resolution of transmission electron microscopy (TEM) to investigate the mechanism of mineral transformation at nano-scale. The applications of TEM- electron energy loss spectroscopy (EELS) for quantification of $Fe(III)/{\Sigma}Fe$ from the K-nontronite formation associated with structural Fe(III) reduction in nontronite under deep subseafloor environment were demonstrated. In particular, quantification of the changes in Fe-oxidation state at nanoscale is essential to understand the mechanisms of minerals formation. The procedure of EELS acquisition, quantitative determination of Fe-oxidation states, and advantages of EELS techniques were discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.226-231
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• 2002

The present study discusses the results of the controlled precipitation of HgTe nanocrystals in a PbTe semiconductor matrix and demonstrates its effectiveness in producing well-organized and crystallographically aligned semiconductor nanocrystals. Following the similar procedure used in metallic alloys, the semiconductor alloys are treated at 600$^{\circ}C$ for 48 hours, quenched and aged up to 500 hours at 300$^{\circ}C$ and 450$^{\circ}C$ to induce homogeneous nucleation and growth of HgTe nanocrystalline precipitates. Examination of the resulting precipitates using transmission electron microscopy (TEM) and high resolution TEM (HRTEM) reveals that the coherent HgTe precipitates form as thin discs along the {100} habit planes making a crystallographic relation of {100}$\sub$HgTe///{100}$\sub$PbTe/ and [100]$\sub$HgTe///[100]$\sub$PbTe/. It is also found that the nato-disc undergoes a gradual thickening and a faceting under isothermal aging up to 500 hours without any noticeable coarsening. These results, combined with the extreme dimension of the precipitates (4 nm in length and sub-nanometer in thickness) and the simplicity of the formation process, leads to the conclusion that controlled precipitation is an effective method for the preparation of the desirable quantum-dot nanostructures.