• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.322-329
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• 2021

Nano-cementitious composites may have defects due to poor dispersion of nanomaterials and fabrication process. These defects can cause critical problems for nano-cementitious composites, but studies related to non-destructive analysis of defects sizes inside nano-cementitious composites are insufficient. This study aims to perform non-destructive analysis of nano-cementitious composites by utilizing ultrasonic and electrical resistance. Various sizes of defects were implemented inside the specimens and the specimens were subjected to ultrasonic non-destructive analysis and electrical resistance non-destructive analysis depending on the size of defects and curing days. As a result of the experiment, ultrasonic pulse velocity decreased by up to 11% as the defects size increased, and the electrical resistance increased by up to 14% depending on the defects size. For this reason, this study concluded that non-destructive analysis using ultrasonic and electrical resistance can predict defects inside nano-cementitious composites.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2003.05a
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• pp.61-61
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• 2003

It is important to know SIze distribution of defects In electroplated trivalent chrome layers because it significantly influences on performance of the layers. Most of the nano-scale defects are able to be introduced by hydrogen evolution during the plating. Little information is available on the nano-size defects. In this study, SANS was applied to determine the size distribution of nano-scale defects in the trivalent chrome layers prepared in a formate bath. The defect size and distribution was dependent upon plating conditions such as current density and applied voltage. SANS is one of useful techniques to determine the nano-scale defect in the electroplated layers.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.170.1-170.1
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• 2016

$Bi_2Te_3$ has long been studied for its excellent thermoelectric characteristics. Recently, this material has been known as a topological insulator (TI). The surface states within the bulk band gap of a TI, which are protected by the time reversal symmetry, contribute to the conduction at the surface, while the bulk is in insulating state. In contrast to the bulk defects tuning the chemical potential to the Dirac energy, the native defects near the surface are expected not to change the shape of the Fermi surface and the related spin structure. Using scanning tunneling microscopy (STM), we have systematically characterized surface or near surface defects in p- and n- doped $Bi_2Te_3$, and identified their structure by first principles calculations. In addition, bias-polarity dependences of STM images revealed the electron donor/acceptor nature of each defect. A detailed theoretical study of the surface states near the Dirac energy reveals the robustness of the Dirac point, which verifies the effectiveness of the disturbance on the backscattering from various kinds of defects.

• Journal of the Korean institute of surface engineering
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• v.37 no.3
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• pp.175-178
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• 2004

The size and number of nano-size defects of thin trivalent chrome layers were determined by small angle neutron scattering (SANS) without breaking the thin chrome layers. Most of defect size of the trivalent chromium prepared in this test conditions is in the range of about 40nm. The number of nano-size defects less than about 40nm of the trivalent chromium layer increases with plating voltage at constant current density From this study, SANS is proved as one of useful techniques to evaluate nano-size defects of thin film layer.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.10
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• pp.831-835
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• 2014

The relative concentration of surface and interfacial defects in hydrothermally grown ZnO nanostructures was investigated by a comparison of two samples having different growth temperatures via bias voltage sweep rate under laser illumination of 405 and 355 nm. The current of small ZnO nanostructures (growth temperature of $75^{\circ}C$) decreased when induced more slowly bias voltage sweep rate under the laser illumination. In contrast, the current of large ZnO nanostructures (growth temperature of $90^{\circ}C$) increased. This difference in currents indicates the relation of relative defects concentration between surface and interfacial defects of ZnO nanostructure. Our experimental approach has potential applicability in the analysis of influence on defects in ZnO devices.

• Transactions on Electrical and Electronic Materials
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• v.5 no.4
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• pp.143-147
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• 2004

Surface defects and bulk defects on SOI wafers are studied. Two new metrologies have been proposed to characterize surface and bulk defects in epitaxial layer transfer (ELTRAN) wafers. They included the following: i) laser scattering particle counter and coordinated atomic force microscopy (AFM) and Cu-decoration for defect isolation and ii) cross-sectional transmission electron microscope (TEM) foil preparation using focused ion beam (FIB) and TEM investigation for defect morphology observation. The size of defect is 7.29 urn by AFM analysis, the density of defect is 0.36 /cm$^2$ at as-direct surface oxide defect (DSOD), 2.52 /cm$^2$ at ox-DSOD. A hole was formed locally without either the silicon or the buried oxide layer (Square Defect) in surface defect. Most of surface defects in ELTRAN wafers originate from particle on the porous silicon.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.2
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• pp.53-59
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• 2004

In this paper, we propose a new multi-purpose Scanning Force Microscope (SFM) system. The system can be used for nano/micro-scratching, in-process profile measurement, and observation of potential surface defects which occur during the scratching in air or liquid. Experimental results of nano/micro-scratching show that the smallest scratching depth can be controlled to be 10nm, which corresponds to the stability of the SFM system. Profile measurements of nano/micro-scratching surfaces have also been performed by the method of on-machine measurement and in-process measurement. Two measurement results were in good agreement with each other. The maximum difference was approximately 10 nm, which was mainly caused by the sampling repeatability error that influences the measurement accuracy Also, micro-defects on the micro-scratching surface were successfully detected by the SFM system. It was confirmed that the number of micro-defects increases when the surface is subjected to a cyclic bending load. The maximum depth was less than 100nm.

• Journal of the Semiconductor & Display Technology
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• v.3 no.4
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• pp.45-49
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• 2004

We examined large particles and filter size effects of Central Chemical Supplying (CCS) system for STI-CMP on Light Point Defects (LPDs) after polishing. As manufacturing process recently gets thinner below 0.1 um line width, it is very important to keep down post-CMP micro-scratch and LPDs in case of STI-CMP. Therefore, we must control the size distribution of large particles in a slurry. With optimization of final filter size, CCS system is one of the solutions for this issue. The oxide and nitride CMP tests were accomplished using nano-ceria slurries made by ourselves. The number of large particles in a slurry and the number of LPDs on the wafer surface after CMP were reduced with decrease of the final filter size. Oxide removal rates slightly changed according to the final filter size, showing the good performance of self-made nano ceria slurries.

• Korean Journal of Materials Research
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• v.14 no.6
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• pp.413-419
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• 2004

Recently, Silicon On Insulator (SOI) devices emerged to achieve better device characteristics such as higher operation speed, lower power consumption and latch-up immunity. Nevertheless, there are many detrimental defects in SOI wafers such as hydrofluoric-acid (HF)-defects, pinhole, islands, threading dislocations (TD), pyramid stacking faults (PSF), and surface roughness originating from quality of buried oxide film layer. Although the number of defects in SOI wafers has been greatly reduced over the past decade, the turn over of high-speed microprocessors using SOI wafers has been delayed because of unknown defects in SOI wafers. A new characterization method is proposed to investigate the crystalline quality, the buried oxide integrity and some electrical parameters of bonded SOI wafers. In this study, major surface defects in bonded SOI are reviewed using HF dipping, Secco etching, Cu-decoration followed by focused ion beam (FIB) and transmission electron microscope (TEM).

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3335-3339
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• 2013

Boron-doped ZnO (BZO) nanorods were grown on quartz substrates using hydrothermal synthesis, and the temperature-dependence of their photoluminescence (PL) was measured in order to investigate the origins of their PL properties. In the UV range, near-band-edge emission (NBE) was observed from 3.1 to 3.4 eV; this was attributed to various transitions including recombination of free excitons and their longitudinal optical (LO) phonon replicas, and donor-acceptor pair (DAP) recombination, depending on the local lattice configuration and the presence of defects. At a temperature of 12 K, the NBE produces seven peaks at 3.386, 3.368, 3.337, 3.296, 3.258, 3.184, and 3.106 eV. These peaks are, respectively, assigned to free excitons (FX), neutral-donor bound excitons ($D^{\circ}X$), and the first LO phonon replicas of $D^{\circ}X$, DAP, DAP-1LO, DAP-2LO, and DAP-3LO. The peak position of the FX and DAP were also fitted to Varshni's empirical formula for the variation in the band gap energy with temperature. The activation energy of FX was about ~70 meV, while that of DAP was about ~38 meV. We also discuss the low temperature PL near 2.251 eV, related to structural defects.