Deposition and x-ray characterization of epitaxial thin films of LaAlO3

Highly epitaxial thin films of lanthanum aluminate (LaAlO3) have been obtained on strontium titanate (SrTiO3) substrates by means of atomic layer deposition using La(thd)3 (Hthd = 2,2,6,6-tetramethylhepta-3,5-dione), Al(CH3)3 and ozone as precursors. The system shows a near linear relationship between pulsed and deposited composition. Thin films with stoichiometric composition have been subject to thermal annealing at 650 °C under oxygen atmosphere, thereby achieving epitaxial films on Ti-O-terminated substrates of SrTiO3. The thin film||substrate epitaxial relationship is determined to be LaAlO3(100)|LaAlO3[100]||-SrTiO3(100)|SrTiO3[100] by use of synchrotron radiation. Selected films were also deposited on LaAlO3(100) to achieve homoepitaxy. This resulted in the observation of split peaks for high q-reflections, pointing towards slight differences in stoichiometry. For ultrathin films, Bragg satellites were observed around the specular reflections, coming from either surface- or interface reconstruction.