Growth conditions and microstructure of Y2O3 buffer layers on cube-textured Ni

Y2O3 films were deposited on cube-textured Ni substrates by electron-beam e vaporation as part of a buffer layer study for YBa2Cu3O7-delta (YBCO) coate d conductors. Their microstructure was observed by scanning electron micros copy (SEM) and transmission electron microscopy (TEM), and their crystallog raphic texture and surface roughness evaluated by X-ray diffraction (XRD) a nd atomic force microscopy (AFM). Previous studies showed the Y2O3 surface normal changed from (100) to (111) on decreasing the deposition chamber pre ssure from 10(-5) to 10(-6) Torr. In this work, 300 nm thick Y-2,O-3, buffe r layers were deposited at two different deposition chamber pressures, simi lar to 5 X 10(-4) Torr N-2 and similar to 2 X 10-5 Torr air, so as to make the (100) orientation dominant. However, the morphology of the Y2O3 buffer layers was significantly affected by changing the deposition chamber pressu re, the lower pressure buffer layer being denser and smoother than that mad e at the higher pressure. The Y2O3 grains in a 600 nm thick Y2O3 buffer lay er grown under 2 X 10-5 Torr air became larger and more uniformly square as the film grew thicker. The Y2O3 grown on thermally grooved Ni deposited at 2 X 10-5 Ton: air, showed (111)-oriented grains near the grooves. This loc al imperfection in the texture could lead to significant barriers to superc urrent flow in the YBCO overlayer. (C) 1999 Elsevier Science B.V. All right s reserved.