Growth mechanisms of laser deposited BiSrCaCuO films on MgO substrates

Atomic force microscopy has been performed on the initial growth stages of Bi2Sr2Ca1Cu2Oy (2212) epitaxial superconducting thin films deposited on MgO by pulsed-laser ablation, We find two growth mechanisms: a two-dimensional (layered) growth and a three-dimensional (island) growth. The two-dimensional mechanism is dominant. We report that Bi2Sr2Ca1Cu2Oy thin films grow unit-cell by unit-cell. The in-plane orientations are determined by X-ray diffraction. We observe three epitaxial states: 2212 [100]//MgO [100], 2212 [100]//MgO [110] and orientation to 12.5 degrees coming from the rotation between the Bi2Sr2Ca1Cu2Oy overlayer and the MgO along the [100] MgO axis, Both orientations 2212 [100]//MgO [100] and 2212 [100]//MgO [110] are due to the high roughness of substrate surface while the orientation to 12.5 degrees is characteristic of the growth of Bi2Sr2Ca1Cu2Oy thin films deposited on MgO by laser ablation, (C) 1998 Elsevier Science B.V.