• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.2
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• pp.247-253
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• 1996

Microscopic analysis has been performed in order to investigate effects of the microstructure of the starting feed rods on the morphology of the S-L interface and the stability of the molten zone during single crystal growth of $SrTiO_{3}$ using a floating zone method. Undoped and $Fe_{2}O_{3}$ doped $SrTiO_{3}$ doped $SrTiO_{3}$ specimens, sintered at the different temperatures have been used. In the case of the feed rods sintered at the lower temperature($1400^{\circ}C$), the poor densification made the stability of the molten zone difficult to maintain. The feed rods sintered at the higher temperature ($1600^{\circ}C$) exhibited the higher density but their molten zone was difficult to maintain due to the presence of the abnormally grown grains. It is concluded that the uniform grain size distribution of the feed rod is the critical factor to maintain the stable molten zone and therefore to give optimum growth condition during FZ single crystal growth.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.4
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• pp.878-885
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• 2008

The FPDs(Flat Panel Displays) such as LCD(Liquid Crystal Display) and PDP(Plasma Display Panel) and OLED(Organic Light Emitting Diode), recently, have been substituted for CRT(Cathode Ray Tube) displays because they have a convex surface, small volume, light weight and lower electric power consumption. The productivity of FPDs is greatly dependent on the area of thin glass panel with 0.6 - 0.8mm thickness because FPDs are manufactured by cutting a large-scaled thin glass panel with patterns to the required product dimensions. So FPD's industries are trying to increase the area of thin glass panel. For example, the thin glass panel size of the 8th generation is 2,200mm in width, 2,600mm in length and 0.7mm in thickness. The air flows both in the thin glass panel and in the porous PE-plate surface were modeled and analyzed, from which a working condition was estimated. The thin glass panel on the porous PE-plate surface with self-lubricating characteristics was investigated and compared with that on the square duct floating bar surface with many holes of 1mm diameter when the thin glass panel contacts the floating bar surface due to malfunction of electric power supply.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.4
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• pp.532-542
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• 1996

The electrical and optical properties of the annealed $LiNbO_{3}$ single crystal with congruently melting composition and MgO or ZnO doped $LiNbO_{3}$ single crystal grown by the FZ method. The electrical and optical properties such as electrical conductivity, dielectric constant (Curie temperature), electro-mechanical coupling factor, optical transmittance and refractive indices of the grown crystals were measured and the nonlinear refractive indices of the grown crystals were calculated theoretically. The doping effects of MgO and ZnO were investigated by comparing the electrical and optical properties of the undoped $LiNbO_{3}$ single crystal and those of the $LiNbO_{3}$ single crystals doped with MgO or ZnO.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.1
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• pp.81-92
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• 1997

Rear floating junction cell (RFJC), using the buried contact technology, is capable of eliminating the efficiency limitations on the single sided cells by providing betterear surface passivation. The implementation of this structure, is simpler and lower in cost and therefore viable for commercial production. However, the contributions, due to damages in the two sets of grooves, to the total dark saturation current density has limited the achievable efficiency of the RFJC to only 21.5 %. This Paper reports on the efficiency estimates of RFJC using PC-1D.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.113-117
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• 2005

Multiferroic $HoMnO_3$ single crystal was prepared using 4-point focused floating zone furnace, and polycrystalline $HoMn_{1-x}\;^57Fe_xO_3$ (x=0.00, 0.01, 0.02, 0.05) powders have been prepared by solid state reaction. Their magnetic and crystallographic properties are studied using MPMS, PPMS, and $M\ddot{o}ssbauer$ spectroscopy. The crystal structure found to be a hexagonal and a magnetic easy-axis is (110) direction. As the external applied magnetic field increases, temperature of the dielectric constant anomaly is decreased. $HoMn_{0.95}\;^{57}Fe_{0.05}O_3$ shows huge quadrupole splitting value from the $M\ddot{o}ssbauer$ spectra.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.10
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• pp.61-66
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• 2007

A gain enhancement rail-to-rail buffer amplifier for liquid crystal display (LCD) source driver is proposed. An op-amp with extremely high gain is needed to decrease the offset voltage of the buffer amplifier. Cascoded floating current source and class-AB control block in the op-amp achieve a high voltage gain by reducing the channel length modulation effect in high voltage technologies. HSPICE simulation in $1\;{\mu}V$ 15 V CMOS process demonstrates that voltage gain is increased by 30 dB. The offset voltage is improved from 6.84 mV to $400\;{\mu}V$. Proposed op-amp is fabricated in an LCD source driver IC and overall system offset voltage is decreased by 2 mV.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.62-66
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• 2002

The conventional floating zone(FZ) crystal and Czochralski(CZ) silicon crystal have resistivity variations longitudinally as well as radially The resistivity variations of the conventional FZ and CZ crystal are not conformed to requirement of dopant distribution for power devices and thyristors. These resistivity variations in conventional cystals limits the reverse breakdown voltage that could be achieved and forced designers of high power diodes and thyristors to compromise the desired current-voltage characteristics. So to produce high Power diodes and thyristors, Neutron Transmutation Doping(NTD) technique is the one method just because NTD silicon provides very homogeneous distribution of doping concentration. This procedure involves the nuclear transmutation of silicon to phosphorus by bombardment of neutron to the crystal according to the reaction $^{30}$ Si(n,${\gamma}$)longrightarrow$^{31}$ Silongrightarrow(2.6 hr)$^{31}$ P+$\beta$$^{[-10]}$ . The radioactive isotope $^{31}$ Si is formed by $^{31}$ Si capturing a neutron, which then decays into the stable $^{31}$ P isotope (i.e., the donor atom), whose distribution is not dependent on the crystal growth parameters. In this research, neutron was irradiated on FZ silicon wafers which had high resistivity(1000~2000 Ω cm), for 26 and 8.3hours for samples of HTS-1 and HTS-2, and 13, 3.2, 2.0 hours for samples of IP-1, IP-2 and IP-3, respectively, to compare resistivity changes due to time differences. The designed resistivities were approached, which were 2.l Ωcm for HTS-1, 7.21 Ω cm for HTS-2, 1.792cm for IP-1, 6.83 Ωcm for IP-2, 9.23 Ωcm for IP-3, respectively. Point defects were investigated with Deep Level Transient Spectroscopy(DLTS). Four different defects were observed at 80K, 125K, 230K, and above 300K.

• Korean Journal of Materials Research
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• v.27 no.7
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• pp.369-373
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• 2017

Unidirectionally solidified TiAl alloys were prepared by optically-heated floating zone method at growth rates of 10 to 70 mm/h in flowing argon. The microstructures and tensile properties of these crystal bars were found to depend strongly on the growth rate and alloy composition. TiAl alloys with composition of 47 and 50 at.%Al grown under the condition of 10 mm/h showed $Ti_3Al({\alpha}_2)/TiAl({\gamma})$ layer structures similar to single crystals. As the growth rate increased, the alloys with 47 and 50 at.%Al compositions showed columnar-grain structures. However, the alloys fabricated under the condition of 10 mm/h had a layered structure, but the alloy with increased growth rate consisted of ${\gamma}$ single phase grains. The alloy with a 53 at.%Al composition showed a ${\gamma}$ single phase regardless of the growth rate. Room-temperature tensile tests of these alloys revealed that the columnar-grained material consisting of the layered structure showed a tensile ductility of larger than 4 % and relatively high strength. The high strength is caused by stress concentration at the grain boundaries; this enhances the secondary slip or deformation twinning across the layered structure in the vicinity of the grain boundaries, resulting in the appreciable ductility.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.859-860
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• 2006

TiC-$TiB_2$-SiC system was a ternary eutectic, whose eutectic composition was 34TiC-$22TiB_2$-44SiC (mol%). TiC-$TiB_2$-SiC ternary eutectic composite were synthesized by a floating zone method using TiC, $TiB_2$ and SiC powders as starting materials. The TiC-$TiB_2$-SiC eutectic composite showed a lamellar texture. TiC(022), $TiB_2(010)$ and SiC(111) of the eutectic composite were perpendicular to the growth direction. TiC-$TiB_2$-SiC ternary eutectic composite had specific relationship among the crystal planes: TiC[011]//$TiB_2[010]$//SiC[112], TiC(200)//$TiB_2$(001)//SiC(402) and $TiC(1\bar{1}1)$//$TiB_2(101)$//SiC(220).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.7
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• pp.1073-1081
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• 2001

Many researches have published numerous papers about the high-strain-rate obtained from Split Hopkinson Pressure Bar(SHPB) tests. And 6.5wt%Si steel is widely known as an excellent magnetic material because its magnetostriction is nearly zero. Single crystals are prepared by the Floating Zone(FZ) method, which melts the alloy by the use of a high temperature electron beam in a pure argon gas condition. In this paper, the fracture behavior of the poly crystals and single crystals (DO$_3$phase) of Fe-6.5wt%Si alloy by SHPB test is observed. The comparison of high-strain-rate results with static results was done. Obtained main results are as follows: (1) Fe-6.5wt%Si alloy has higher strength at high-strain-rate tensile. SHPB results of polycrystal are twice as high as static results. (2) From the fractography, the cleavage steps are remarkably reduced in the SHPB test compared with the static test.