• Journal of the Korean Solar Energy Society
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• v.31 no.1
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• pp.37-43
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• 2011

In this paper, the optimized doping condition of crystalline silicon solar cells with $156{\times}156\;mm^2$ area was studied. To optimize the drive-in temperature in the doping process, the other conditions except variable drive-in temperature were fixed. These conditions were obtained in previous studies. After etching$7\;{\mu}m$ of the surface to form the pyramidal structure, the silicon nitride deposited by the PECVD had 75~80nm thickness and 2 to 2.1 for a refractive index. The silver and aluminium electrodes for front and back sheet, respectively, were formed by screen-printing method, followed by firing in 400-425-450-550-$850^{\circ}C$ five-zone temperature conditions to make the ohmic contact. Drive-in temperature was changed in range of $830^{\circ}C$ to $890^{\circ}C$to obtain the sheet resistance $30{\sim}70\;{\Omega}/{\box}$ with $10\;\Omega}/{\box}$ intervals. Solar cell made in $890^{\circ}C$ as the drive-in temperature revealed 17.1% conversion efficiency which is best in this study. This solar cells showed $34.4\;mA/cm^2$ of the current density, 627 mV of the open circuit voltage and 79.3% of the fill factor.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.407-411
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• 2022

Bulk-sized PbTiO₃ (PT), which is widely known as a high-performance ferroelectric oxide but cannot be fabricated into a monolithic ceramic due to its high c/a ratio, was successfully prepared with a high tetragonality by partially substituting Ni ions for Pb ions using a solid-state reaction method. We found that Ni-doped PT was well-fabricated as a bulk monolith with a significant c/a ratio of ~1.06. X-ray diffraction on as-sintered and crushed samples revealed that NiTiO₃ secondary phase was present at the doping level of more than 2 at.%. Scanning electron microscopic study showed that NiTiO₃ secondary phase grew on the surface of PT specimens regardless of the doping level possibly due to the evaporation of Pb during sintering. We demonstrated that an unconventional introduction of Ni ions into A-site plays a key role on the fabrication of bulk PT, though how Ni ion functions should be studied further. We expect that this study contributes to a further development of displacive ferroelectric oxides with a high c/a ratio.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.10a
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• pp.141-144
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• 1997

High quality 3C-SiC epilayer was grown on Si(111) at 125$0^{\circ}C$ using chemical vapor deposition(CVD) technique by pyrolyzing tetramethylsilane(TMS). 3C-SiC epilayer was doped by tetramethylgallium(TMGa) during the CVD growth. The crystallinity of 3C-SiC was significantly enhanced by doping the gallium impurity.

• Progress in Superconductivity
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• v.10 no.2
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• pp.123-127
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• 2009

NaFeAs recently observed superconductivity with the maximum $T_c{\approx}25$ K is investigated using first principles approach. We will address briefly the electronic structure and contrast other superconducting pnictides. This system shows strong two-dimensionality and reduction of flatness in the Fermi surfaces undermines tendencies of magnetic or charge instabilities. As observed in other superconducting pnictides, $Q_M=(\pi,\pi,0)$ antiferromagnetic ordering, which has not been observed clearly yet in this compound, is energetically favored. However, contrast to other superconducting pnictides, the density of states in this ordering shows considerable electron-hole asymmetry, implying efficiency of hole-doping than electron-doping to enhance $T_c$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.3
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• pp.157-160
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• 2002

The ferroelectric domain variation and electrical performance of $Pb(Zr,Ti)O_{3}$ (PZT) based capacitors through La additions were systematically studied. La substitution up to 10 % was performed to lower the coercive and saturation voltages of epitaxial ferroelectric capacitors grown on Si using a (Ti_{0.9}Al_{0.1})N/Pt$ conducting barrier composite. Ferroelectric capacitors substituted with 10 % La show significantly lower coercive voltage compared to capacitors with 0 % and 3 % La. This is attributed to a systematic microstructure change into $180^{\circ}C$ domain and decrease in the tetragonality (i.e., c/a ratio) of the ferroelectric phase. These capacitors show promise as storage elements in low power memory architectures.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.1
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• pp.19-22
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• 1999

N-doped and low-hydrogenated DLC thin films were coated on the Mo-tip FEAs in order to improve the field emission performance and their electrical properties were evaluated. The fabricated devices showed improved field emission performance in terms of turn-on voltage, emission current and current fluctuation. This result might be caused both by the shift of Fermi level toward conduction band by N-doping and by the inherent stability of DLC material. Furthermore, the transconductance of the DLC-coated Mo-tip FEA and electrical conductivity and optical band-gap of the deposited DLC films were investigated.

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.41-41
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• 2008

• Journal of the Korean Ceramic Society
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• v.36 no.4
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• pp.372-379
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• 1999

Hihg-toughened ceria-stabilized tetragonal zirconia ceramics with irregular grain shape and undulated grain boundary was prepared by ceria doping. Irregularity of grain shapes was increased with the amount of doped ceria. But in case of the large amount of doped ceria grain boundary was migrated to the reverse direction of DIGM. Ceria-stabilized zirconia ceramics annealed at 1650$^{\circ}C$ for 2h after twice dippings into cerium nitrate solu-tion of 0.2M and sintering at 1500$^{\circ}C$ for 2h showed the highest grain boundary length with a value of 23.6$\mu\textrm{m}$ Ceria concentration difference between convex and concave sides in irregular grains was observed over 1 mol% but not observed in normal grains, Specimens with normal grain shape showed intergranular fracture mode whereas the specimens with irregular grain shape showed transgranular fracture mode.

• Korean Journal of Materials Research
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• v.14 no.5
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• pp.334-337
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• 2004

Perovskite PMN-PZT-based ceramics were prepared and the$ MnO_2$ doping effects on their piezoelectric properties were investigated. Grain size decreased with increasing the $MnO_2$ content, and the pyrochlore phase was not identified in the sintered PMN-PZT ceramics with 0.01～1.0wt% $MnO_2$. Piezoelectric voltage and charge constants were reduced and mechanical quality factor increased with increasing the $MnO_2$ content. However, electromechanical coupling coefficient slightly decreased with increasing the MnO$_2$ content without regard to the grain size.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.193.1-193.1
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• 2007