Investigation On Preparing Technology Of SrTiO₃ And LaMnO₃ Films By Chemical Vapor Deposition

For preparation of the second-generation high-temperature superconducting tape YBa₂Cu₃O_7-x(YBCO),the perovskite oxide SrTiO₃(STO)and LaMnO₃(LMO)had been considered as ideal buffer layer materials due to the very small lattice mismatch and the closest thermal expansion coefficient with YBCO.Besides,STO and LMO also can effectively prevent element diffusion and transfer excellent texture for YBCO tape.Traditional methods for preparing STO and LMO thin films are physical deposition methods such as pulsed laser deposition,radio frequency sputtering,etc.,while chemical vapor deposition has the advantages of low cost and great repeatability.Therefore,chemical vapor deposition has been used to prepare STO and LMO films as buffer layers for YBCO tape.STO film was prepared on quartz glass by laser chemical vapor deposition at a deposition temperature(T_dep)ranged from 760 to 1104 K.Effect of the laser and T_dep on the orientation,crystallinity,texture,and microstructure of the STO film was investigated.As the T_dep was increased,the preferred orientation of the STO film tended to be(110)?orientated with corresponding texture coefficient(TC)on the(110)reflection enhanced from 2.3 to 6.Meanwhile,the full width at half maximum(FWHM)of the??scan on the(110)reflection decreased from 0.85°to 0.59°.The(110)?oriented grains were in wedge shape and about 60×150 nm in size,which tended to be flat at an elevated T_depof 1104 K.LMO film was prepared on quartz substrate at a T_dep ranged from 773 to 1173 K by chemical vapor deposition.Effect of the T_dep on the orientation,crystallinity,texture,and microstructure of the LMO film was investigated.At 923-973 K,the LMO films were strong(100)orientation and high crystallinity,whose FWHM of the?-scan on(200)reflection were 0.27°and 0.26°,respectively.The(100)-oriented LMO film which consisted of edgeless rectangular grains showed a columnar growth on the cross section.The TC of(200)reflection reached a maximum of 3.7 at T_dep=973 K.The deposition rate(R_dep)showed a maximum of 11.9?m h^-1 at T_dep=773 K.