• Journal of the Korean Magnetic Resonance Society
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• v.24 no.1
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• pp.9-15
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• 2020

Nitrogen vacancy center (NV center) in diamond has recently been appeared as a promising candidate for hyperpolarization applications due to its optical pumping property by laser. Optically Detected Magnetic Resonance (ODMR) has been used as a conventional method to obtain the resonance spectrum of NV centers. ODMR, however, has a shortcoming of sensitivity and a limitation of subjects, such that the degree of hyperpolarization can hardly be estimated, and that the spins other than NV centers are invisible. In contrast, Electron Spin Resonance (ESR) spectroscopy is known to proportionally reflect the degree of spin polarization. In this work, we successfully observed the optically-induced hyperpolarization of NV spins in diamond through CW-ESR spectroscopy with an X-band system. All the NV peaks were identified by calculating the eigenvalues of NV spin Hamiltonian. The intensities of NV peaks were enhanced over 240 times after optical pumping. The enhanced peaks corresponding to the transition from |m_s=0> to |m_s=-1> revealed inverted phases, while other peaks remained in-phase. The optically-induced hyperpolarization on NV spins can be a useful polarization source, leading to ¹³C nuclear hyperpolarization in diamond.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2172-2174
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• 2005

MgO has been used as the material of the protecting layer for AC PDP. AC PDP is influenced by characteristics of the surface glow discharge on the MgO thin film. Because MgO thin film is practically discharge electrodes, the discharge characteristics of MgO thin film should be varied with the method of deposition. In this study, changing order and time of deposition, we use electron beam evaporation system and R.F reactive magnetron sputtering system in the MgO deposition. Particularly, after using electron beam evaporation system, we use R.F. reactive magnetron sputtering system in the MgO deposition, then we could get lower amount of charge and higher luminance efficiency than only using electron beam evaporation system.

• Laser Solutions
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• v.18 no.4
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• pp.1-5
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• 2015

For continuous laser micro patterning on three-dimensional free form surface, innovative laser system is developed. The two axis galvanometer is combined with the dynamic focusing unit to increase optical distance. Also, it is synchronized with the 3 axis mechanical system. To determine laser machining sequence, laser CAM system is developed. It can make possible of 3D surface micro patterning under $25{\mu}m$ pattern width. The uniformity of pattern width is about 2.8% and it is validated that focal plane is well conserved by the dynamic focusing unit. Velocity and positional information of 1 axis is stage is fed to the scanner control board by the encoder signal and it makes possible real time synchronization. With this system, possible patterning volume is enlarged from $40{\times}40mm^2$ to $40{\times}120{\times}30mm^3$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.366-371
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• 2022

Recently many efforts have been made to develop a novel class of non-fullerene electron acceptor materials for high-performance organic solar cells. In this work, anthraquinone derivatives, TMAQ and THAQ, were prepared and their availability as electron acceptor materials for organic solar cells were investigated in terms of optical, thermal, electrochemical properties, and solar cell devices. Compared to TMAQ, a significant bathochromic shift of absorption band was observed for THAQ owing to intramolecular hydrogen-bond-assisted CT interactions. Thanks to the fused aromatic ring structure and benzoquinone unit, both TMAQ and THAQ exhibited a high thermal stability and an efficient electron reduction process. In particular, the intramolecular O-H---O=C hydrogen bond of THAQ plays an important role in improving the thermal stability and electron reduction properties. In the P3HT:acceptor solar cell system, THAQ-based devices had more than ca. 6 times higher power conversion efficiency than TMAQ -based devices. These results serve as a guide for developing high-efficient anthraquinone-based electron acceptor materials.

• Journal of the Optical Society of Korea
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• v.7 no.3
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• pp.145-149
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• 2003

The anisotropy of electron energy distribution in oxygen plasmas produced by a high intensity laser was investigated by using polarization spectroscopy. An ultra-short pulsed laser with a pulse duration of 66.5 fs and a power density of $1 {\times} 10^17/ W/$\textrm{cm}^2$$ was used. At this power density and pulse duration, the plasma was generated predominantly by optical field ionization. The degree of polarization of OVI 1s$^2$2p$^2$p2- 1s$^2$4d$^2$D$^{0}$ (J = 1/2-3/2 and 3/2-5/2) transition line at 129.92 $\AA$ was measured. O VI 1s$^2$2p$^2$P$^2$ -1s$^2$4s$^2$S$^2$ (J = 1/2-1/2 and 3/2-1/2) transition line at 132.26 $\AA$ was used to calibrate the sensitivity of the optical system. The dependencies of the degree of polarization on the initial gas density and on the laser polarization were investigated. When the laser polarization was changed from a linear to a circular polarization, the degree of polarization was decreased. When the initial gas density was increased, the degree of polarization was decreased.

• Korean Journal of Materials Research
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• v.25 no.3
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• pp.125-131
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• 2015

Fluorine-doped $SnO_2$ (FTO) thin film/Ag nanowire (NW) double layers were fabricated by means of spin coating and ultrasonic spray pyrolysis. To investigate the optimum thickness of the FTO thin films when used as protection layer for Ag NWs, the deposition time of the ultrasonic spray pyrolysis process was varied at 0, 1, 3, 5, or 10 min. The structural, chemical, morphological, electrical, and optical properties of the double layers were examined using X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, the Hall effect measurement system, and UV-Vis spectrophotometry. Although pure Ag NWs formed isolated droplet-shaped Ag particles at an annealing temperature of $300^{\circ}C$, Ag NWs covered by FTO thin films maintained their high-aspect-ratio morphology. As the deposition time of the FTO thin films increased, the electrical and optical properties of the double layers degraded gradually. Therefore, the double layer fabricated with FTO thin films deposited for 1 min exhibited superb sheet resistance (${\sim}14.9{\Omega}/{\Box}$), high optical transmittance (~88.6 %), the best FOM (${\sim}19.9{\times}10^{-3}{\Omega}^{-1}$), and excellent thermal stability at an annealing temperature of $300^{\circ}C$ owing to the good morphology maintenance of the Ag NWs covered by FTO thin films.

• Journal of the Optical Society of Korea
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• v.17 no.6
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• pp.548-558
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• 2013

In this work, laser induced breakdown spectroscopy (LIBS) is used to investigate soil samples collected from different desert areas of Riyadh city in Saudi Arabia. Both qualitative analysis and plasma parameters are studied via the observed LIBS spectra. These experiments have been done using a Spectrolaser-7000 system with 50 mJ fundamental wavelength of Nd:YAG laser and detection delay time of 1 microsecond. Many spectral lines are highly resolved for many elements like Al, Fe, Mg, Si, Mn, Na, Ca and K. The electron temperatures Te and electron densities Ne, for the constituent of generated LIBS plasma, are determined for all the collected samples. It is found that both Te and Ne vary from one desert area to other. This variation is due to the change of the elemental concentration in different desert areas that affects the sample's matrices. Time dependent measurements have also been performed on the soil samples. While the signal-to-base ratio (SBR) reached its optimal value at 1 microsecond, the plasma parameters Ne and Te reach values of $4{\times}10^{17}cm^{-3}$ and 9235 K, respectively, at 2.5 microsecond. The later indicate that the plasma cooling processes are slow in comparison to the previously observed results for metallic samples. The observed results show also that in the future it is possible to enhance the exploitation of LIBS in the remote on-line environmental monitoring application, by following up only the values of Ne and Te for one element of the soil desert sample using an optical fiber probe.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.2
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• pp.74-78
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• 2019

$Zn_2SnO_4$ thin films were deposited on quartzs substrates by using radio-frequency magnetron sputtering system. Thermal treatments at various temperatures were performed to evaluate the effect of annealing temperatures on the properties of $Zn_2SnO_4$ thin films. Surface morphologies were examined by using field emission-scanning electron microscopy and showed that sizes of grains were slightly increased and grain boundaries were clear with increasing annealing temperatures. The deposited $Zn_2SnO_4$ thin films on quartzs substrates were amorphous structures and no distinguishable crystallographic changes were observed with variations of annealing temperatures. The optical transmittance was improved with increasing annealing temperatures and was over 90% in the wavelength region between 350 and 1100 nm at the annealing temperature of $600^{\circ}C$. The optical energy bandgaps, which derived from the absorbance of $Zn_2SnO_4$ thin films, were increased from 3.34 eV to 3.43 eV at the annealing temperatures of $450^{\circ}C$ and $600^{\circ}C$, respectively. As the annealing temperature was increased, the electron concentrations were decreased. The electron mobility was decreased and resistivity was increased with increasing annealing temperatures with exception of $450^{\circ}C$. These results indicate that heat treatments at higher annealing temperatures improve the optical and electrical properties of rf-sputtered $Zn_2SnO_4$ thin films.

• Journal of the Korean Magnetic Resonance Society
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• v.19 no.1
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• pp.11-17
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• 2015

The Kubo formalism and utilizing the projection operator technique (POT) introduced by Kawabata, the electron spin resonance (ESR) line-shape formula for carbon nanotubes through the hyperfine interaction introduced earlier in terms of POT. We can see that the line-width decreases exponentially as the temperature increases. The spin relaxation time show gradual decrease as magnetic field becomes larger. The analysis reveals the peculiarities in spin relaxation inherent to one dimensional system at low temperature and weak magnetic fields. Thus, the present technique is considered to be more convenient to explain the carbon nanotubes as in the case of other optical transitions.

• Journal of Advanced Navigation Technology
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• v.2 no.2
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• pp.126-131
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• 1998

In optical scanning holography, 3-D holographic information of an object is generated by 2-D active optical scanning. The optical scanning beam can be a time-dependent Gaussian apodized Fresnel zone plate. In this technique, the holographic information manifests itself as an electrical signal which can be sent to an electron-beam-addressed spatial light modulator for coherent image reconstruction. This technique can be applied to 3-D optical remote sensing especially for identifying flying objects. In this paper, we first briefly review optical scanning holography and analyze the resolution achievable with the system. We then present mathematical expression of real and virtual image which are responsible for holographic image reconstruction by using Gaussian beam profile.