Preparation Of YBCO High-temperature Superconducting Films And Buffer Layer Films By Laser Chemical Vapor Deposition

Due to its high irreversible field,critical temperature?T_C?and critical current density?J_C?,the second generation high-temperature superconducting YBa₂Cu₃O_7-??YBCO?materials are extensively applied in each area.Currently,for preparation of YBCO high-temperature superconducting thin films,various approaches such as metal organic deposition?MOD?,pulsed laser deposition?PLD?,metal organic chemical vapor deposition?MOCVD?and laser chemical vapor deposition?LCVD?have been used.However,because laser photons can reduce reaction activation energy between reaction atoms and promote chemical reaction,LCVD is regarded as the most potential method of preparation of high quality YBCO thin film.In this paper,high-quality YBCO high-temperature superconducting thin films were prepared on SrTi O₃ single crystal substrates by spray atomizing and coprecipitating laser chemical vapor deposition?SAC-LCVD?.In addition,high-quality CeO₂ buffer layer films also were grown on?100?MgO single crystal substrates by LCVD using solid precursor,and the effects of films deposition parameters on orientation,microstructure and performance indicators of the YBCO high temperature superconducting thin films and CeO₂ buffer layer thin films were investigated.For preparation of YBCO films on?001?SrTiO₃ single crystal substrates,c-axis-oriented YBCO films with the deposition rate(R_dep)of 14?m h^-1,critical temperature of 91 K and critical current density of 2.4 MA cm^-2 were prepared at laser power?P_L?increased to 167 W,which showed an epitaxial growth mode of YBCO[001]//SrTiO₃[001]?YBCO[100]//SrTiO₃[100]?.As the laser power was reduced,the orientation of YBCO films changed from c-axis to a-axis,resulting a decrease in electrical properties of YBCO films.For the present study,deposition parameters of YBCO films with optimizing electrical properties were found.Different areas have different demands for YBCO high-temperature superconducting thin films with different preferred orientations.To further investigate how to prepared YBCO films with different preferred orientations,this paper prepared a-axis-,c-axis-,?103?/?110?-and?113?-oriented YBCO films on?001?,?110?and?111?SrTiO₃ single crystal substrates,respectively.For a-axis-oriented YBCO film,its in-plane epitaxial growth relationship was YBCO[100]//SrTiO₃[001]?YBCO[001]//SrTiO₃[100]?,and epitaxial growth relationship of c-axis-oriented YBCO film was YBCO[001]//SrTiO₃[001]?YBCO[100]//SrTiO₃[100]?.For the?103?/?110?-oriented and?113?-oriented YBCO film,their corresponding in-plane epitaxial growth relationship were YBCO[110]//SrTi O₃[110]?YBCO[010]//SrTiO₃[010]?and YBCO[100]//SrTiO₃[100](YBCO[113]//SrTiO₃[111],respectively.In study of CeO₂ buffer layer film,?100?MgO single crystal was used as substrate.For CeO₂ film prepared on MgO single crystal substrate,the full width at half maximum?FWHM?of the?-scan on?200?reflection and that of the?-scan on?220?reflection of the CeO₂ film were 1.0°and 2.1°,respectively.The?100?-oriented CeO₂ showed cube-on-cube epitaxial growth,which had rectangular grains on the surface and columnar grains in cross section.The deposition rate ranged from 16 to 24?m h^-1.