The dielectric and piezoelectric properties of the ferroelectric BaTiO3 were measured and analyzed using both strong and weak electric field conditions. To measure the electric field induced polarizations and strains, a high voltage source and the measuring circuit were used and the dielectric constants were measured with an impedance analyzer. The spontaneous polarization of BaTiO3 at room temperature was calculated as 17 μC/cm2 based on the lattice structure and internal ion location, which is in good agreement with the experimental results. The polarization and strain hysteresis curve according to the electric field were analyzed in terms of lattice structure and ion position. The magnitude of remanent polarization is proportional to the offset distance of Ti4+ ion from the lattice center. The magnitude of dielectric permittivity is proportional to the degree to which Ti4+ ion can move freely inside the lattice. The magnitude of piezoelectric constant d33 is proportional to how much Ti4+ ion distorts the lattice as it moves inside the lattice.
TiO2 (Ti(1-x)Nb(x)O2, x= 0.04~0.06) transparent conducting oxide film was fabricated by RF magnetron sputtering process and their electrical, optical, stability properties were studied. When the Nb 4 at% sputtering target was used with RF power 120 W, pressure 8 mTorr, post-annealing temperature 60 0℃, the resistivity of TNO film was 4×10(-4) Ω-cm. The optical transmittance in the visible wavelength was ca. 86%. TNO films require heat treatment during or after the deposition process. When the film was deposited at room temperature and post-annealed at 600℃, the lowest resistivity was obtained. When the TNO film was exposed to high temperature and humidity, the resistivity of the film was rather decreased. The stability to temperature and humidity implies that the TNO film could be a appropriate candidate for In-free, ZnO-free transparent conducting oxide materials.
The high cost of crystalline silicon solar cells has been considered as one of the major obstacles to their terrestrial applications. Spin on doping (SOD) is presented as a useful process for the manufacturing of low cost solar cells. Phosphorus (P509) was used as an n-type emitters of solar cells. N-type emitters were formed on p-type EFG ribbon Si wafers by using a SOD at different spin speed (1,000∼4,000 rpm), diffusion temperatures (800℃∼950℃), and diffusion time (5∼30 min) in N2+O2 atmosphere. With optimum condition, we were able to achieve cell efficiency of 14.1%.
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SiC Contaminations in Polycrystalline-Silicon Wafer Directly Grown from Si Melt for Photovoltaic Applications Ye-Neung Lee, Bo-Yun Jang, Jin-Seok Lee, Joon-Soo Kim, Young-Soo Ahn, Woo-Young Yoon Journal of the Korea Foundry Society.2013; 33(2): 69. CrossRef
Ribbon silicon solar cells have been investigated because they can be produced with a lower material cost. However, it is very difficult to get good texturing with a conventional acid solution. To achieve high efficiency should be minimized for the reflectance properties. In this paper, acid vapor texturing and anti-reflection coating of SiNx was applied for EFG Ribbon Si Wafer. P-type ribbon silicon wafer had a thickness of 200 um and a resistivity of 3 n-㎝. Ribbon silicon wafers were exposed in an acid vapor. Acid vapor texturing was made by reaction between the silicon and the mixed solution of HF: HNO3. After acid vapor texturing process, nanostructure of less than size of 1 um was formed and surface reflectance of 6.44% was achieved. Reflectance was decreased to 2.37% with anti-reflection coating of SiNx.
A Study on the Enhancement of Cooling Efficiency for the Cabinet of Automatic Controller in the Interior of Industrial Building Soon-Ho Kim, Hyun-Jung Park Journal of the Korea Society For Power System Engineering.2013; 17(6): 79. CrossRef
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