Morphology and microstructure of BaTiO3/SrTiO3 superlattices grown on SrTiO3 by laser molecular-beam epitaxy

The morphology and microstructure of BaTiO3/SrTiO3 (BTO/STO) superlattices grown epitaxially on STO (001) substrates by a computer-controlled laser mo lecular-beam epitaxy deposition system have been characterized by means of atomic force microscopy and high-resolution transmission electron microscop y (HRTEM). It is found that the HRTEM images taken along the [120] directio n of BTO and STO show the maximal contrast difference. It is, therefore, ob served that the superlattices consist of a highly oriented and single-cryst alline multilayered structure. As identified by HRTEM, the number of unit c ells in each BTO or STO layer matches very well with that obtained from ref lection high-energy electron diffraction oscillations. The surfaces and int erfaces of the superlattices are atomically smooth. In the superlattices, t he ratio between the c axis of BTO and STO is about 4% larger than that mea sured from BTO or STO bulk crystals. (C) 1999 American Institute of Physics . [S0003-6951(99)01848-3].