Growth of TlBa2Ca2Cu3Oy superconducting thin film on CeO2 buffered sapphire substrate

Abstract We report the growth of TlBa 2 Ca 2 Cu 3 O y superconducting thin film on CeO 2 buffered r-cut sapphire substrate by amorphous phase epitaxy method, wherein an amorphous phase of a composition, TlBa 2 Ca 3 Cu 4 O y was deposited by rf magnetron sputtering and subsequently crystallized by annealing at high temperatures in a closed system. There exists an optimum thickness of about 200 A of CeO 2 buffer layer that gives a smooth buffer layer surface. At the temperature around 840 °C we get only Tl-2212 phase and for a longer annealing time it results in Tl-1212 phase. At higher temperatures Ba reacts with Ce to form BaCeO 3 . To avoid this reaction process we introduced another amorphous buffer layer, TlSr 2 CaCu 2 O y onto CeO 2 layer. By this method we could prepare a good quality Tl-1223 thin film which showed a T c of 104 K and a J c =0.3 MA/cm 2 at 77 K and 0.1 T field.