Preparation Of GdBa₂Cu₃O_7-? Films And Gd₂CuO₄ Buffer Layers By Chemical Vapor Deposition And Their Structure Investigation

GdBa₂Cu₃O_7-??GdBCO?has attracted many researchers'attention due to its high critical current density and excellent electrical performance in high-intensity magnetic field.As an important method for preparing thin film materials,Metal Organic Chemical Vapor Deposition?MOCVD?technique has wide application prospects in industrial mass production of GdBCO superconducting films.GdBCO films,Gd₂CuO₄ films and GdBCO/Gd₂CuO₄ bilayer films were deposited on polycrystal and single crystal substrates by MOCVD technique.X-ray diffraction?XRD?,pole figure,field emission scanning electron microscopy?FESEM?,transmission electron microscopy?TEM?and Raman spectra were employed to investigate the effects of deposition conditions such as substrates,deposition temperature,deposition pressure and oxygen partial pressure on phases of films,out-of-plane and in-plane orientation,epitaxial growth relationship,microstructure,deposition rate,etc.The main results are listed as following.?1?GdBCO films were deposited on polycrystalline Al₂O₃,single crystalline?100?MgO,?100?STO and?100?LAO substrates.GdBCO phase was obtained on polycrystalline substrates,but GdBCO phase and c-axis-oriented GdBCO epitaxial films were obtained on single crystalline substrates.The best deposition temperature was 990 ^oC.At deposition temperature of 990 ^oC,intensity of?00l?peaks was the strongest and orientation of films was the best with no impurities and smooth surface.The epitaxial growth relationship of c-axis-oriented GdBCO film and LAO substrate was GdBCO[100]//LAO[010]and GdBCO[001]//LAO[100].?2?Gd₂CuO₄ films were deposited on polycrystalline Al₂O₃ and single crystalline?100?STO substrates.Gd₂CuO₄ phase was obtained on polycrystalline substrates,but Gd₂CuO₄ phase and c-axis-oriented Gd₂CuO₄ epitaxial films were obtained on single crystalline substrates.The best deposition temperature was 1080^oC.At deposition temperature of 1080 ^oC,intensity of?00l?peaks was the strongest and orientation of films was the best without impurities.Also,full width at half maximum value of X-ray diffraction patterns reached the minimum which showed that the best crystallinity.The epitaxial growth relationship of c-axis-oriented Gd₂CuO₄ film and STO substrate was Gd₂CuO₄[100]//STO[010]and Gd₂CuO₄[001]//STO[100].?3?C-axis-oriented GdBCO/Gd2CuO4 epitaxial bilayer films were deposited on?100?STO single crystal substrates.The best deposition temperature was 1010 ^oC.At deposition temperature of 1010 ^oC,thickness of Gd₂CuO₄ film was 0.6?m and thickness of GdBCO film was 1.4?m.At this deposition temperature,intensity of?00l?peaks was the strongest and orientation of bilayer films was the best with minimum defects.The epitaxial growth relationship of c-axis-oriented GdBCO/Gd₂CuO₄ bilayer film and STO substrate was GdBCO[100]//Gd₂CuO₄[100]//STO[010]and GdBCO[001]//Gd₂CuO₄[001]//STO[100].