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rf-sputtering을 이용한 $MgB_2$ 박막 제작
안종록,황윤석,이순걸 한국초전도학회 2003 Progress in superconductivity Vol.4 No.2
We have studied fabrication of $MgB_2$ thin film on $SrTiO_3$ (001) and r-cut $A1_2$$O_3$ substrates by rf magnetron sputtering method using and $ MgB_2$ single target and two targets of Mg and B, respectively. Based on P -T phase diagram of $MgB_2$ and vapor pressure curves of Mg and B, a three-step process was employed. B layer was deposited at the bottom to enhance the film adhesion to the substrate. Secondly, co-sputtering of Mg and B was done. Finally, Mg was sputtered on top to compensate fur the loss of Mg during annealing. Subsequently, $MgB_2$ films were in-situ annealed in various conditions. The sample fabricated using the three-step process showed $T_{c}$ of 24 K and formation of superconducting $MgB_2$ phase was confirmed by XRD spectra. In case of co-sputtering deposition, $T_{c}$ depended on annealing time and argon pressure. However, those made by single-target sputtering showed non-superconducting behavior or low transition temperature, at best.est.
안종록,이순걸,박창준 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.4
An ideal ion source should create stable ion beams of sufficient intensity with an ion energy spread as low as possible. Most electron-impact ion sources used in mass spectrometers have been based on the design by Nier. Calculation of the potential distribution in the ion source revealed that the ion extraction efficiency could be improved by applying a positive repeller potential to the ionization chamber, which is normally at ground potential in a Nier-type ion source. Ion kinetic-energy distributions were measured in a Nier-type ion source and in a modified ion source by applying a retarding pole bias potential to the quadrupole at various emission currents and chamber pressures. As the emission current or the chamber pressure was increased, the most probable energy was shifted to a higher energy in both ion sources. However, the ion kinetic-energy spread was smaller and varied less in the modified ion source while it was larger in the conventional Nier-type ion source.
Noise Properties of Directly-coupled Single-layer High-Tc 2nd-order SQUID Gradiometer
황윤석,안종록,강찬석,이순걸,김진태 한국초전도학회 2002 Progress in superconductivity Vol.3 No.2
We have fabricated planar-type single-layer second-order high-Tc SQUID gradiometers. The devices consisted of symmetrically designed three parallel-connected square pickup loops that were directly coupled to the SQUID. $YBa_2$$Cu_3$$O_{7}$ film was deposited on $SrTiO_3$ substrate by a PLD system and patterned into a device by the photolithography with ion milling technique. Junctions of the SQUID were either step-edge or bicrystal type. All the structures were formed on a 10 mm $\times$ 5 mm substrate. Balancing of the gradiometer was achieved by adjusting the width of the central pickup loop. The gradiometer noise was measured both inside and outside a magnetically shielded room. Details of the results will be discussed.
Rf co-sputtering으로 제작한 MgB$_2$ 박막의 in-situ 열처리 효과
김윤원,안종록,이순걸,이규원,김인선,박용기 한국초전도학회 2004 Progress in superconductivity Vol.5 No.2
We have studied effects of in-situ annealing on the fabrication of superconducting MgB$_2$ thin films prepared by rf magnetron co-sputtering. The Films were deposited on A1$_2$O$_3$ (1102) substrates at room temperature by using Mg and B targets. To trap remnant $O_2$ gas in the chamber, we used 20 mtorr Af sputter-gas balanced with 5 mol % of H$_2$ gas. To enhance adhesion to the substrate a thin layer of B was deposited prior to the codeposition of Mg and B. After completion of the film deposition, an additional Mg layer was deposited on top to compensate for Mg loss during the subsequent in-situ annealing. We have investigated the effects of two most important annealing parameters that are the Mg-to-B composition ratio and the annealing temperature. The range of the Mg-to-B composition ratio was from 0.42 to 0.85, and that of the annealing temperature was 500 $^{\circ}C$∼750 $^{\circ}C$. The Best result was obtained for the composition ratio of about 10% Mg excess from the stoichiometry and the annealing temperature of 700 $^{\circ}C$. Based on these results, we obtained films with T$_{c}$ : 36.5 K by further refining the fabrication process.s.