DIELECTRIC, PYROELECTRIC AND STRUCTURAL-PROPERTIES OF LITAO3 THIN-FILMS GROWN ON SILICON BY A MODIFIED MOLECULAR-BEAM EPITAXY

Polycrystalline lithium tantalate (LiTaO3) thin films have been prepar ed using a modified molecular beam epitaxy process on silicon (111) su bstrates which have an epitaxial platinum silicide (PtSi) buffer layer serving as a growth template and oxygen barrier. X-ray photoelectron spectroscopy on the films showed a stoichiometric composition. X-ray d iffraction revealed a preferentially oriented polycrystalline structur e with LiTaO3 (012) parallel to the surface. Atomic force microscope m easurements on a 200 nm film showed growth islands with typical diamet ers of 0.4 mu m and a root mean square roughness of 50 nm. For the fir st time, the ferroelectric properties of these very thin LiTaO3 films (< 0.5 mu m) grown on silicon substrates have been investigated. The s amples show a phase transition temperature between 580 and 650 degrees C, a coercive field of 15 similar to 22 kV/cm and an apparent spontan eous polarization up to 1 mu C/cm(2). The pyroelectric current respons e showed a value of 100 similar to 200 mu A/W.