摘要
High-quality epi-MgO buffer layers under different O2/Ar pressure ratios are fabricated by rf magnetron sputtering on textured IBAD-MgO templates. Under the total deposition pressure remaining constant （14 Pa）, the effect of changing the ratio of O2/Ar pressure from 1：4 to 3：2 on the microstructure and surface morphology of epi-MgO films is studied. The microstructure and morphology of epi-MgO are fully characterized by x-ray diffraction, atom force microscope and scanning electron microscope. The best texture quality of epi-MgO with an out-plane Δω value of 1.8° and an in-plane Δ？ value of 5.22° are obtained under the ratio of O2/Ar pressure 3：2. Further, the surface morphology indicates that the surface of epi-MgO is smooth with rms surface roughness about 4.7 nm at O2/Ar pressure ratio 3：2. After that, GdBa2Cu3O7？δ （GBCO） layers are deposited on the CeO2 cap layer buffered epi-MgO/IBAD-MgO templates to assess the efficiency of such a buffer layer stack. The critical current density of GBCO films （thickness of 200 nm） is higher than 3 MA/cm2, indicating that epi-MgO/IBAD-MgO is promising for depositing superconducting layers with a higher critical current density.
High-quality epi-MgO buffer layers under different O2/Ar pressure ratios are fabricated by rf magnetron sputtering on textured IBAD-MgO templates. Under the total deposition pressure remaining constant （14 Pa）, the effect of changing the ratio of O2/Ar pressure from 1：4 to 3：2 on the microstructure and surface morphology of epi-MgO films is studied. The microstructure and morphology of epi-MgO are fully characterized by x-ray diffraction, atom force microscope and scanning electron microscope. The best texture quality of epi-MgO with an out-plane Δω value of 1.8° and an in-plane Δ？ value of 5.22° are obtained under the ratio of O2/Ar pressure 3：2. Further, the surface morphology indicates that the surface of epi-MgO is smooth with rms surface roughness about 4.7 nm at O2/Ar pressure ratio 3：2. After that, GdBa2Cu3O7？δ （GBCO） layers are deposited on the CeO2 cap layer buffered epi-MgO/IBAD-MgO templates to assess the efficiency of such a buffer layer stack. The critical current density of GBCO films （thickness of 200 nm） is higher than 3 MA/cm2, indicating that epi-MgO/IBAD-MgO is promising for depositing superconducting layers with a higher critical current density.
基金
Supported by the National High-Tech Research and Development Program of China under Grant No 2009AA032402, the Youth Fund of the National Natural Science Foundation of China under Grant No 11204174, the International Thermonuclear Experimental Reactor Plan under Grant No 2011GBl13004, and the Shanghai Science and Technology Committee under Grant Nos 09DZ206000 and 11DZl100402.
