[en] Sr_0.75Ba_0.25Nb₂O₆ (SBN75) thin films were deposited on silicon substrate with MgO (100) or TiN (100) buffer layer by radio-frequency magnetron sputtering technique. X-ray diffraction confirmed that a 900 deg. C annealed SBN self-buffer layer introduced before SBN deposition can lead to the highly c-axis orientation of SBN75 thin film on MgO buffer layer. Energy-dispersive spectrometry analysis showed that the SBN75 films had target-film composition transfer and the TiN buffer layer was partially oxidized during SBN growth. The refractive index of SBN films on both MgO/Si and TiN/Si substrates was determined by fitting the measured reflectance curves with Sellmeier dispersion model in the visible region and the micro-structures were studied by scanning electron microscopy. In this paper, the conditions for SBN/MgO/Si treated as waveguide structure were also discussed.

[en] An improved hybrid physical chemical vapor deposition (HPCVD) method for the preparation of magnesium diboride (MgB₂) films is proposed. In this experiment, the temperature for the evaporation of magnesium is set to be ∼700 deg. C, while the substrate is kept below 500 deg. C. Inside the vacuum chamber, double heaters control the temperature for the evaporation of Mg and of the substrate independently. The deposition of MgB₂ films on a polycrystalline Al₂O₃ substrates is obtained by the reaction between evaporated magnesium atoms and boron atoms that decompose from diborane near the heaters. The superconducting MgB₂ films show a transition temperature at 38.5 K and a zero-resistance temperature at 38 K. The critical current density of the films is 10⁵ A/cm²