Surface evolution and dynamic scaling of heteroepitaxial growth of (La,Ba)MnO3 films on SrTiO3 substrates by rf magnetron sputtering

We have investigated the evolution of (La0.7Ba0.3)MnO3 (LBMO) surfaces epitaxially grown on SrTiO3 (001) substrates using high-resolution X-ray scattering and atomic force microscopy (AFM) measurements. At an early stage of growth, highly strained LBMO epilayers were formed and nearly pseudomorphic growth of LBMO epilayers on SrTiO3 substrates was expected. For these thin layers, roughness varied with thickness through a scaling exponent β = 0.102 ± 0.01. As the LBMO epilayer thickness attained 72 nm, the growth front of the film became quite rough, which is related to the relief of strain. From AFM images, distinct large 3-D islands were formed on the rough film surface in the regime of rapid roughening; this regime is described with a scaling exponent β = 0.734 ± 0.01. An effective critical thickness of a LBMO film epitaxially grown on a SrTiO3 substrate is experimentally determined to be about 50-72 nm.