Growth of LaAlO3 on silicon via an ultrathin SrTiO3 buffer layer by molecular-beam epitaxy

(001)-oriented LaAlO3 films were grown epitaxially on (001) Si substrates utilizing an ultrathin 5 unit-cell-thick SrTiO3 buffer layer. The SrTiO3 layer was grown at ∼250 °C and annealed in vacuum at 550 °C, following an epitaxy-by-periodic-annealing procedure. Upon this buffer layer, the LaAlO3 layer was then grown by codeposition at 580 °C. The rocking curve of the as-grown LaAlO3 film exhibits a full width at half maximum value as small as 0.02°. Atomic force microscopy shows that the surface of the LaAlO3 film has a root-mean-square roughness of 1.3 A. Scanning transmission electron microscopy reveals that the LaAlO3/SrTiO3 interface and the SrTiO3/Si interfaces are sharp. This high crystalline quality, twin-free, epitaxial LaAlO3 on SrTiO3 on silicon could be relevant to integrating oxides with multiple functionalities on silicon.