• Progress in Superconductivity
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• v.5 no.1
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• pp.80-83
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• 2003

Superconducting YBCO thin films are fabricated on single-crystalline substrates by Metallo-organic Depostion process employing Trifluoroacetic acid as a chelating agent (MOD-TFA). (100)-oriented single crystalline LaAlO$_3$ substrates were employed to grow superconducting film with high crystallinity. The fully processed YBCO thin films were characterized with XRD, SEM, EDS, etc. The microstructures of YBCO thin films show labyrinth-like patterns. The origin of this microstructure was delineated by compositional inhomogeneity during the MOD process and it was shown that the microstructure may be modified by additives. In this work, effects of additives on the microstructures and electrical properties of YBCO thin films have been investigated.

• Journal of the Korean Ceramic Society
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• v.33 no.3
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• pp.313-320
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• 1996

We have fabricated an in-plane aligned a-axis oriented YBa2Cu3O7-x (a-YBCO) thin film on a LaSrGaO4(100) substrate with a PrBa2Cu3O7-x(PBCO) template layer by two step plused laser deposition using 308 nm XeCl excimer laser. A YBCO layer and PBCO layer grown at low temperatures were used as template layers. We have investigated the effect of the deposition temperature of template layers on the superconducting and struc-tural properties of in-plane aligned a-YBCO thin films. An optimal deposition temperature of the PBCO template layers was 630. In-plane aligned a-YBCO thin films showed an anisotropy ratio in resistivity of 11.5 and a zero resistance temperature of 88 K.

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.115-118
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• 1991

The temperature distribution on the superconducting thin-film is analyzed as moving constant field is applied above upper critical field. The distribution of magnetic field is derived in the normal spot. Governing equation is obtained with the help of the equation of conservation of energy. The temperature distribution and the heat dissipation are obtained through computer simulation by the method of numerical analysis. Maximum temperature is occured in the most right side inside normal spot. The temperature is increased abruptly inside the normal spot, and decreased more gradually outside normal spot in the direction of moving field as velocity is increased. Increasing the velocity rather than increasing magnitude of the normal spot and the applied field makes maximum temperature larger. Heat dissipation is affected by the velocity rather than the magnitude of normal spot and the applied field.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.12
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• pp.573-577
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• 2002

We designed wideband HTS antennas which consists of two triangle -radiation patches using a $YBa_2Cu_3O_{7-X}$ (YBCO) superconducting thin film. The major limitation of high-Tc superconducting (HTS) microstrip antennas is the narrow bandwidth due to the high Q and thin substrate. Defining bandwidth as the frequency range over which standing wave ratio (SWR) 2:1 or less, HTS antenna bandwidths are typically 0.85 % to 1.1 %. Thus considerable effort has been focused on developing antennas for broadband operation. To calculate input impedance and design of the broadband HTS antennas a moment method technique was used. The HTS antenna fabricated in this work was designed for K-band, which is useful band for satellite to satellite communications. The bandwidth obtained was a significant 6.7 % and the other measured performance of our HTS antenna, including the bandwidth, radiation Pattern, efficiency, standing wave ratio (SWR) and return losses was reported.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.523-526
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• 2002

We designed wideband HTS antennas which consists of two triangle-radiation patches using a YBa$_2$Cu$_3$O$\sub$7-x/ (YBCO) superconducting thin film. The major limitation of high-Tc superconducting (HTS) microstrip antennas is the narrow bandwidth due to the high Q and thin substrate. Defining bandwidth as the frequency range over which standing wave ratio (SWR) 2:1 or less, HTS antenna bandwidths are typically 0.85% to 1.1%. Thus considerable effort has been focused on developing antennas for broadband operation. To calculate input impedance and design of the broadband HTS antennas a moment method technique was used. The HTS antenna fabricated in this work was designed for K-band, which is useful band for satellite-to-satellite communications. The bandwidth obtained was a significant 6.7% and the other measured performance of our HTS antenna, including the bandwidth, radiation Pattern, efficiency, standing wave ratio (SWR) and return losses was reported.

• 한국초전도학회:학술대회논문집
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• v.12
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• pp.20-20
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• 2002

• Progress in Superconductivity and Cryogenics
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• v.16 no.3
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• pp.7-9
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• 2014

Single-crystal like $MgB_2$ thin film was grown on (000l) $Al_2O_3$ substrate by using hybrid physical-chemical vapor deposition (HPCVD) system. Single crystal properties were studied by X-ray diffraction (XRD) and the full width at half maximum (FWHM) of the (0001) $MgB_2$ peak is $15^{\circ}$, which is very close to that has been reported for $MgB_2$ single-crystal. It indicates that the crystalline quality of thin film is good. Temperature dependence on resistivity was investigated by physical property measurement system (PPMS) in various applied fields from 0 to 9 T. The upper critical field ($H_{c2}$) and irreversibility field ($H_{irr}$) were determined from PPMS data, and the estimated values are comparable with that of $MgB_2$ single-crystals. The thin film shows a high critical temperature ($T_c$) of 40.4 K with a sharp superconducting transition width of 0.2 K, and a high residual resistivity ratio (RRR=21), it reflects that $MgB_2$ thin film has a pure phase structure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.11
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• pp.1029-1034
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• 2003

The Bi$_2$Sr$_2$Ca$_{n}$Cu$_{n+1}$ O$_{x}$, superconducting thin films arc fabricated by using the sputtering and evaporation method. Because we confirmed the sticking ratio of Bi element in the Bi$_2$Sr$_2$Ca$_{n}$Cu$_{n+1}$ O$_{x}$ superconducting thin film fabricated by using the sputtering method was much lower than the expected value, to get the enough number of the flakes of Bi, faraday cup was used to evaporate Bi clement. As a result of the fabrication, Bi 2201 and Bi 2212 single phases could be made by the optima of deposition condition. And we confirmed the sticking coefficient of Bi element was clearly related to the temperature change of the substrate and the generation of Bi22l2 phase

• Progress in Superconductivity and Cryogenics
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• v.15 no.3
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• pp.5-8
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• 2013

We have studied Hall effect for potassium (K)-doped $BaFe_2As_2$ superconducting thin films by analyzing the relation between the longitudinal resistivity (${\rho}_{xx}$) and the Hall resistivity (${\rho}_{xy}$). The thin films used in this study were fabricated on $Al_2O_3$ (000l) substrates by using an ex-situ pulsed laser deposition (PLD) technique under a high-vacuum condition of ~$10^{-6}$ Torr. The samples showed the high superconducting transition temperatures ($T_c$) of ~ 40 K. The ${\rho}_{xx}$ and the ${\rho}_{xy}$ for K-doped $BaFe_2As_2$ thin films were measured by using a physical property measurement system (PPMS) with a temperature sweep (T-sweep) mode at an applied current density of $100A/cm^2$ and at magnetic fields from 0 up to 9 T. We report the T-sweep results of the ${\rho}_{xx}$and the ${\rho}_{xy}$ to investigate Hall scaling behavior on the basis of the relation of ${\rho}_{xy}={A{\rho}_{xx}}^{\beta}$. The ${\beta}$ values are $3.0{\pm}0.2$ in the c-axis-oriented K-doped $BaFe_2As_2$ thin films, whereas the thin films with various oriented-directions like a polycrystal showed slightly lower ${\beta}$ than that of c-axis-oriented thin films. Interestingly, the ${\beta}$ value is decreased with increasing magnetic fields.

• 한국초전도학회:학술대회논문집
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• v.13
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• pp.55-55
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• 2003