• Journal of the Korean Society for Heat Treatment
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• v.15 no.3
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• pp.113-117
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• 2002

Fatigue characteristics of ferroelectric $Pb(Zr,Ti)O_3$ (PZT) based capacitors through donor doping is reported in this paper. La substitution up to 10% were carried out to study systematically the fatigue behaviors of epitaxial ferroelectric capacitors grown on Si using $(Ti_{0.9}Al_{0.1})N/Pt$ conducting barrier composite. Ferroelectric capacitors substituted with 10% La show sufficient low voltage switched polarization and fatigue free performance. Systematic decrease in the tetragonality of the ferroelectric phase (i.e., c/a ratio) results in the corresponding reduction in coercive voltage, sufficient remnant polarization at 1.5-3V, and good fatigue property.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.37-40
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• 2001

This paper presents the modeling methodology of Zinc diffusion process applied for high-speed avalanche photodiode fabrication using neural networks. Three process factors (sealing pressure, amount of Zn$_3$P$_2$ source per volume, and doping concentration of diffused layer) are examined by means of D-optimal design experiment. Then, diffusion rate and doping concentration of Zinc in diffused layer are characterized by a static response model generated by training fred-forward error back-propagation neural networks. It is observed that the process models developed here exhibit good agreement with experimental results.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.7
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• pp.76-84
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• 1994

The characteristics of 3 inch wafer scale GaAs epitaxial wafer grown by molecular beam epitaxy for LSI process application were studied. The thickness and doping uniformity are characterized and discussed. The growth temperature and growth rate were $600^{\circ}C$ by pyrometer, and 1 $\mu$m/h, respectively. It was found that thickness and doping uniformity were 3.97% and 4.74% respectively across the full 3 inch diameter GaAs epitaxial layer. Also, ungated MESFETs have been fabricated and saturation current measurement showed 4.5% uniformity on 3 inch, epitaxial layer, but uniformity of threshold voltage increase up to 9.2% after recess process for MESFET device.

• New & Renewable Energy
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• v.18 no.1
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• pp.29-34
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• 2022

The most prevalent cause of solar cell efficiency loss is reduced recombination at the metal electrode and silicon junction. To boost efficiency, a a SiO_X/poly-Si passivating interface is being developed. Poly-Si for passivating contact is formed by various deposition methods (sputtering, PECVD, LPCVD, HWCVD) where the ploy-Si characterization depends on the deposition method. The sputtering process forms a dense Si film at a low deposition rate of 2.6 nm/min and develops a low passivation characteristic of 690 mV. The PECVD process offers a deposition rate of 28 nm/min with satisfactory passivation characteristics. The LPCVD process is the slowest with a deposition rate of 1.4 nm/min, and can prevent blistering if deposited at high temperatures. The HWCVD process has the fastest deposition rate at 150 nm/min with excellent passivation characteristics. However, the uniformity of the deposited film decreases as the area increases. Also, the best passivation characteristics are obtained at high doping. Thus, it is necessary to optimize the doping process depending on the deposition method.

• Transactions on Electrical and Electronic Materials
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• v.15 no.2
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• pp.87-90
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• 2014

The effects of electric field frequency on the ac electrical treeing phenomena in an epoxy/reactive diluent/layered silicate (1.5 wt%) were carried out, in needle-plate electrode arrangement. A layered silicate was exfoliated in an epoxy base resin, by using our ac electric field apparatus. To measure the treeing propagation rate, constant alternating current (AC) of 10 kV with three different electric field frequencies (60, 500 and 1,000 Hz) was applied to the specimen, in needle-plate electrode arrangement, at $30^{\circ}C$ of insulating oil bath. As the electric field frequency increased, the treeing propagation rate increased. At 500 Hz, the treeing propagation rate of the epoxy/PG/nanosilicate system was $0.41{\times}10^{-3}$ mm/min, which was 3.4 times slower than that of the epoxy/PG system. The electrical treeing morphology was dense bush type at 60 Hz; however, as the frequency increased, the bush type was changed to branch type, having few branches, with very slow propagation rate.

• Nuclear Engineering and Technology
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• v.38 no.1
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• pp.93-98
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• 2006

The radial uniformity of neutron irradiation in silicon ingots for neutron transmutation doping (NTD) at HANARO is examined by both calculations and measurements. HANARO has two NTD holes named NTD1 and NTD2. We have been using the NTD2 hole for 5 in. NTD commercial service, and we intend to use two holes for 6 in. NTD. The objective of this study is to predict the radial uniformity of 6 in. NTD at the two holes. The radial neutron flux distributions inside single crystal and noncrystal silicon loaded at the NTD2 hole are calculated by the VENTURE code. For NTD1, the radial distributions of the reaction rate for a 6 in. NTD with a neutron screen are calculated by MCNP, and measured by gold wire activation. The results of the measurements are compared with those of the calculations. From the VENTURE calculation, it is confirmed that the neutron flux distribution in the single crystal silicon is much flatter than that in the non-crystal silicon. The non-uniformities of the measurements for radial neutron irradiation are slightly larger than those of the calculations. However, excluding local dips in the measurements, the overall trends of the distributions are similar. The radial resistivity gradient (RRG) for a 5 in. silicon ingot is estimated to be about $1.5\%$. For a 6 in. ingot, the RRG of a silicon ingot irradiated at HANARO is predicted to be about $2.1\%$. Also, from the experimental results, we expect that the RRG would not be larger than $4.4\%$.

• Journal of Electrochemical Science and Technology
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• v.4 no.3
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• pp.102-107
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• 2013

The electrochemical properties of Mg-doped $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ and pure $LiFe_{0.5}Mn_{0.5}PO_4$ olivine cathodes are examined and the lattice parameters are refined by Rietveld analysis. The calculated atomic parameters from the refinement show that $Mg^{2+}$ doping has a significant effect in the olivine $LiFeMnPO_4$ structure. The unit cell volume is 297.053(2) ${\AA}^3$ for pure $LiFe_{0.5}Mn_{0.5}PO_4$ and is decreased to 296.177(1) ${\AA}^3$ for Mg-doped $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ sample. The doping of $Mg^{2+}$ cation with atomic radius smaller than $Mn^{2+}$ and $Fe^{2+}$ ion induces longer Li-O bond length in $LiO_6$ octahedra of the olivine structure. The larger interstitial sites in $LiO_6$ octahedra facilitate the lithium ion migration and also enhance the diffusion kinetics of olivine cathode material. The $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ sample with larger Li-O bond length delivers higher discharge capacities and also notably increases the rate capability of the electrode.

• Journal of the Korean Ceramic Society
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• v.48 no.2
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• pp.168-172
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• 2011

Alumina powder was added in a general porcelain (Backja) with clay, feldspar and quartz contents to promote the mullite ($3Al_2O_3{\cdot}2SiO_2$) generation in the porcelain. Low melting materials ($B_2O_3(450^{\circ}C)$, $MnO_3(940^{\circ}C)$, CuO($1080^{\circ}C$)) were doped at ~3 wt% to modify the sinterability of porcelain with a high alumina contents and promote the mullite generation. Green body was made by slip casting method with blended slurry and then, they were fired at $1280^{\circ}C$ for 1hr by a $2^{\circ}C/min$. Densifications of samples with high alumina contents (20~30 wt%) were impeded. As the doping contents of low melting materilas increased, the sinterability of samples was improved. The shrinkage rate and bulk density of samples were improved by doping with low melting materials. Mullite phase increased with increasing the low melting contents in the phase analyses. This means lots of alumina and quartz were transformed into mullite phase by low melting contents doping. In the results, high bending strength of samples with high alumina contents was accomplished by improving the densification and mullite generation in the porcelain.

• Journal of the Korean Ceramic Society
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• v.45 no.3
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• pp.167-171
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• 2008

Zirconium-doped $Li_{1.1}Co_{1-x}Zr_xO_2(0{\leq}x{\leq}0.05)$ powders as cathode materials for lithium ion batteries were synthesized using an ultrasonic spray pyrolysis method. Cyclic voltammetry and cyclic stability tests were performed, and the changes of microstructure were observed. The solubility limit of zirconium into $Li_{1.1}CoO_2$ was less than 5 mol%, and monoclinic $Li_2ZrO_3$ phase was formed above the limit. The Zr-doping suppressed the grain growth and increased the lattice parameters of the hexagonal $LiCoO_2$ phase. The Zr-dopiong of 1mol% resulted in the best cyclic performance in the range of $3.0{\sim}4.3V$ at 1C rate (140 mA/g); the initial discharge capacity decreased from 158 mAh/g to 60 mAh/g in the undoped powder, while from 154 mAh/g to 135 mAh/g in the Zr-doped powder of 1 mol% after 30 cycles. The excellent cycle stability of Zr-doped powder was due to the low polarization during chargedischarge processes which resulted from the delayed collapse of the crystal structure of the active materials with Zr-doping.

• Korean Journal of Materials Research
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• v.32 no.4
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• pp.210-215
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• 2022

Extensive research is being carried out on Ni-rich Li(Ni_xCo_yMn_1-x-y)O₂ (NCM) due to the growing demand for electric vehicles and reduced cost. In particular, Ni-rich Li(Ni_xCo_yMn_1-x-y-zAl_z)O₂ (NCMA) is attracting great attention as a promising candidate for the rapid development of Co-free but electrochemically more stable cathodes. Al, an inactive element in the structure, helps to improve structural stability and is also used as a doping element to improve cycle capability in Ni-rich NCM. In this study, NCMA was successfully synthesized with the desired composition by direct coprecipitation. Boron and tin were also used as dopants to improve the battery performance. Macro- and microstructures in the cathodes were examined by microscopy and X-ray diffraction. While Sn was not successfully doped into NCMA, boron could be doped into NCMA, leading to changes in its physicochemical properties. NCMA doped with boron revealed substantially improved electrochemical properties in terms of capacity retention and rate capability compared to the undoped NCMA.