Direct scanning tunneling microscopy observation of non-unit-cell growth of YBa2Cu3O7-δ thin films

Abstract

The surface morphology of thin YBa2Cu3O 7-δ films grown on LaSrAlO4 (001) and SrTiO 3 (001) by pulsed laser deposition was studied by scanning tunneling microscopy (STM). STM was carried out in ultra high vacuum without prior exposure of the films to air. In the STM images, stacks of terraces which are separated by steps of various heights were observed. Some steps were shorter than the YBa2Cu3O7-δ unit cell height c≈1.2 nm. We present evidence of the fact that the YBa2Cu 3O7-δ thin film surface exhibits different terminations. The microstructure revealed from the STM images implies a non-unit-cell growth mechanism. © 1996 American Institute of Physics.