• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.9
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• pp.2000-2006
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• 2011

In this paper, the drain induced barrier lowering(DIBL) for doping distribution in the channel has been analyzed for double gate MOSFET(DGMOSFET). The DGMOSFET is extensively been studing because of adventages to be able to reduce the short channel effects(SCEs) to occur in convensional MOSFET. DIBL is SCE known as reduction of threshold voltage due to variation of energy band by high drain voltage. This DIBL has been analyzed for structural parameter and variation of channel doping profile for DGMOSFET. For this object, The analytical model of Poisson equation has been derived from Gaussian doping distribution for DGMOSFET. To verify potential and DIBL models based on this analytical Poisson's equation, the results have been compared with those of the numerical Poisson's equation, and DIBL for DGMOSFET has been investigated using this models.

• Journal of the Korean Chemical Society
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• v.32 no.3
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• pp.171-178
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• 1988

The potential energy of adsorbate molecules in the main channel of $K^+$ ion exchanged zeolite L(K-L) was calculated. In K-L which adsorbs three molecules per unit cell, the interaction energies of $H_2O,\;NH_3,\;CH_3NH_2,\;(CH_3)_2NH,\;and\;(CH_3)_3N$ molecules with zeolite lattice are 61.11, 62.31, 65.68, 74.65, and 79.88kJ/mol, respectively. These values are less by 3.7∼12.6kJ/mol than $K^+$ ion affinities with adsorbing molecules. These results may be due to the facts that the electrostatic energies are reduced by the negative charge of the lattice oxygens. The distribution of adsorption sites of $NH_3$ and $CH_3NH_2$ in K-L was investigated by a technique of temperature programmed desorption. The experimental value of desorption energies of $NH_3$ and $CH_3NH_2$ on K-L are in good agreement with the theoritical values. It is concluded that the desorption of $NH_3$ and $CH_3NH_2$ on K-L is the first-order desorption with free readsorption.

• Journal of the Korean Vacuum Society
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• v.6 no.1
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• pp.85-90
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• 1997

A new ionized sputtering process was developed to fill small trench or via using additional ionizing mechanism of sputtered particles from 32cm $AlCu_x$(x=0.5%) cathode target with rotating magnet, then drawn toward substrate by small negative DC potential. The radial uniformity in RFI magnetron sputtering was studied by plasma diagnosis and appropriate RFI coil design to improve it. Optical emission intensities of excited species. $Ar^{\circ}, \;Ar^+;Al^+, \;Al^{\circ}$ are measured across the radial direction and showed close correlation with deposit's bottom to top thickness ratios in trenches and vias of submicron opening and 1.5 aspect ratio. After increase of the diameter of RF coil from 29 cm to 32 cm and improved the power leading feedthrough symmetry by removal of asymmetric single turn region, there was an increase of uniformity from 7.5% to 1.5% in bottom to top thickness ratio in 0.6 $\mu\textrm{m}$ vias.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.315-315
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• 2010

양성자 빔을 이용하여 두경부 암 치료를 South Africa의 iTHEMBA에서 시행하고 있다. 200 MeV의 양성자 빔라인으로부터 진공에서 대기로 인출하여 노즐을 통과하여 종양세포에 조사된다. 치료계획에 적합하게 빔에너지와 모양을 변환하고, 빔을 모니터링하는 기계적 장치들이 노즐에 구성된다. 빔라인에는 이온챔버, Steering Magnet, Multi-wire 이온챔버, Range trimmer plates, lead scattering plate, Double-wedge energy degrader, Multi-layer Faraday cup, Range modulator, Range monitor, occluding ring, Shielding collimators, Quadrant and monitor ionization chamber, Treatment collimator, 그리고 Wellhofer dosimetry tank로 구성되어 있다. 총길이는 6.6m이며 노즐 끝에서 환자의 isocenter 까지는 30cm 정도 아래에 위치한다. 상기의 배치를 갖는 시스템의 양성자 scattering system의 성능을 MCNPX v2.5.0 Monte Carlo simulation을 실시하였다. 또한 정확한 선량을 실시간으로 측정하는 방법인 투과형 검출기를 개발하여 치료와 빔 특성을 동시에 수행하는 기술개발연구가 보고되고 있다. 본 연구에서는 Multileaf Faraday Cup (MLPC) 검출기 설계구조와 데이터 측정방법에 관한 연구를 수행하고자 한다. 빔의 전송 방향으로 3개층의 $4{\times}4$ 배열의 구조로 48 channel의 전류값을 측정하여 입자빔의 분포를 실시간으로 관측하고, 측정된 전류는 ADC를 거쳐 치료계획에 의해 선택된 영역의 SOBP를 유지하도록 range modulation propeller를 조절하는 feed-back system을 갖춘 방사선치료빔 실시간 측정장치 개발에 관한 결과를 보고하고자 한다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.2
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• pp.73-80
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• 1990

The formation of Ti-silicides with the type of substrate, the species and the concentration of dopant, and the annealing temperature was investigated with sheet resistance and thickness measurement, elemental depth profilling, and microstructure. It was directly affected by the type of substrate, the species and the concentration of dopant, and the annealing temperature. For the amorphous Si substrate, the smothness of $TiSi_2/Si$ interface was increased. Above concentr-ation of $1{\times}10^{16}ions/cm^2$, the rate of $TiSi_2/Si$ formation was decreased and the sheet resistance was increased. The initial profile of dopant according to the implantation energy was one of the factors influencing the out-diffusion of dopant. In $POCI_3$ process, this was less than in ion implantation process.

• Journal of the Mineralogical Society of Korea
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• v.30 no.1
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• pp.21-29
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• 2017

Surface soils on Barton Peninsula, King George Island, West Antarctica were investigated to acquire the mineralogical and geochemical data of soil in Antarctica. Multiline of techniques for example, X-ray diffraction (XRD), transmission electron microscopy (TEM)-electron energy loss spectroscopy (EELS), and wet chemistry analysis were performed to measure the composition of clay minerals, Fe-oxidation states, cation exchange capacity, and total cation concentration. Various minerals in sediments such as smectite, illite, chlorite, kaolinite, quartz and plagioclase were identified by XRD. Fe-oxidation states of bulk soils showed 20-40% of Fe(II) which would be ascribed to the reduction of Fe in clays as well as Fe-bearing minerals. Moreover, redox states of Fe in smectite structure was a ~57% of Fe(III) consistent to the values for the bulk soils. The cation exchange capacity of bulk soils ranged from 100 to 300 meq/kg and differences were not significantly measured for the sampling locations. Total cations (Mg, K, Na, Al, Fe) of bulk soils varies, contrast to the heavy metals (Co, Ni, Cu, Zn, Mn). These results suggested that composition of bed rocks influenced the distribution of elements in soil environments and soils containing clay compositions may went through the bio/geochemical alteration.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.14-17
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• 2006

[ $AIFeO_3$ ]has been studied by x-ray diffraction (XRD), vibrating sample magnetometer, Mossbauer spectroscopy. The crystal structure is found to orthorhombic with the lattice parameters being $a_0=4.983\;{\AA},\;b_0=8.554\;{\AA},\;c_0=9.239\;{\AA}$, Magnetic hysteresis curve for $AIFeO_3$ showed weakly ferromagnetic phase at room temperature and a asymmetric shape dependent on the direction of applied field at low temperature. The Curie temperature determined by the temperature dependence of magnetization is 250 K. Mossbauer spectra of $AIFeO_3$ have been taken from 4.2 K to 295 K. Isomer shift at room temperature are found to be $0.11\~0.32\;mm/s$, which is consistent with ferric state. The absorption lines widths become broader with increasing temperature, which is attributed to the Fe ions distribution of each cation site and anisotropy energy difference of each sublattice.

• Journal of Radiation Protection and Research
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• v.24 no.4
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• pp.195-203
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• 1999

It is difficult to determine dosimetric characteristics for small field photon beams since such small fields do not achieve complete lateral electronic equilibrium and have steep dose gradients. Dosimetric characteristics of small field 4, 6, and 10 MeV photon beams have been measured in water with a diamond detector and compared to measurements using small volume cylindrical and plane parallel ionization chambers. Percent depth dose (PDD) and beam profiles for 6 and 10 MeV photon beams were measured with diamond detector and cylindrical ion chamber for small fields ranging from $1{\times}1\;to\;4{\times}4cm^2$. Total scatter factors($S_{c,p}$) for 4, 6, and 10 MeV photon beams were measured with diamond detector, cylindrical and plane parallel ion chambers for small fields ranging from $1{\times}1\;to\;4{\times}4cm^2$. The $S_{c,p}$ factors obtained with three detectors for 4, 6, and 10 MeV photon beams agreed well ($\pm1.2%$) for field sizes greater than $2{\times}2,\;2.5{\times}2.5,\;and\;3{\times}3\;cm^2$, respectively. For smaller field sizes, the cylindrical and plane parallel ionization chambers measure a smaller $S_{c,p}$ factor, as a result of the steep dose gradients across their sensitive volumes. The PDD values obtained with diamond detector and cylindrical ionization chamber for 6 and 10MeV photon beams agreed well ($\pm1.5%$) for field sizes greater than $4{\times}4\;cm^2$. For smaller field sizes, diamond detector produced a depth-dose curve which had a significantly shallower falloff than that obtained from the measurements of relative depth-dose with a cylindrical ionization chamber. For the measurements of beam profiles, a distortion in terms of broadened penumbra was observed with a cylindrical ionization chamber since diamond detector exhibited higher spatial resolution. The diamond detector with small sensitive volume, near water equivalent, and high spatial resolution is suitable detector compared to ionization chambers for the measurements of small field photon beams.

• Journal of the Korean Chemical Society
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• v.40 no.5
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• pp.295-301
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• 1996

A series of solid solutions of the $CaGa_1-xFexO_3-y$ system with the compositions of x=0.25, 0.50, 0.75, and 1.00 has been prepared at $1150^{\circ}C$ under an atmospheric air pressure. The structure, nonstoichiometric chemical formula, and the distribution of cations for the solid solutions are determined by X-ray diffraction analysis, Mohr salt titration, Mossbauer spectroscopic analysis. Their physical properties are discussed with electrical conductivity and magnetic measurements. The crystal system of all the compositions is a brownmillerite orthorhombic system from the X-ray diffraction analysis and the reduced lattice volume increases linearly with x value except that of the composition of x=0.25. All the solid solutions do not contain $Fe^{4+}$ ion and the mole number of oxygen vacancies or y value is 0.50 from Mohr salt analysis. The oxidation state of Fe ion, the coordination state, the structure change in the Brownmillerite-type structure, and the distribution of $Ga^{3+}$ and $Fe^{3+}$ ions are discussed with Mossbauer spectroscopic analysis. The electrical conductivity increases and activation energy decreases, as x value increases. The traditional semiconducting property of this system is described in terms of band theory. The compositions of x=0.50∼1.00 show a thermal magnetic hysteresis in the magnetic measurement with the cooling conditions, which is discussed in terms of the space group and Dzyaloshinsky-Moriya interaction.

• The Journal of Korean Society for Radiation Therapy
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• v.28 no.2
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• pp.87-99
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• 2016

Purpose : This study will evaluate the clinical utility by applying clinical schematic that uses monoenergy or dual energy as according to the location of tumors to the stereotactic radiotherapy to compare the change in actual dose given to the real tumor and the dose that locates adjacent to the tumor. Materials and Methods : CT images from a total of 10 patients were obtained and the clinical planning were planned based on the volumetric modulated arc therapy on monoenergy and dual energy. To analyze the change factor in the tumor, Comformity Index(CI) and Homogeneity Index(HI) and maximum dose quantity were each calculated and comparing the dose distribution on normal tissues, $V_{10}$ and $V_5$, first ~ fourth ribs closest to the tumor ($1^{st}{\sim}4^{th}$ Rib), Spinal Cord, Esophagus and Trachea were selected. Also, in order to confirm the accuracy on which the planned dose distribution is really measured, the 2-dimensional ion chamber array was used to measure the dose distribution. Results : As of the tumor factor, CI and HI showed a number close to 1 when the two energies were used. As of the maximum dose, the front chest wall showed 2% and the dorsal tumor showed equivalent value. As of normal tissue, the front chest wall tumors were reduced by 4%, 5% when both energies were used in the adjacent rib and as of trachea, reduced by 11%, 17%. As of the dose in the lung, as of $V_{10}$, it reduced by 1.5%, $V_5$ by 1%. As of the rear chest wall, when both energies were used, the ribs adjacent to the tumors showed 6%, 1%, 4%, 12% reduction, and in the lung dose distribution, $V_{10}$ reduced by 3%, and $V_5$ reduced by 3.1%. The dose measurement in all energies were in accordance to the results of Gamma Index 3mm/3%. Conclusion : It is considered that rather than using monoenergy, utilizing double energy in the clinical setting can be more effectively applied to the superficial tumors.