Physical characterization of lithium niobate thin films on silicon substrates

The structure and orientation of radio frequency sputtered lithium niobate (LiNbO$\sb3$) films on silicon substrates is determined using x-ray diffraction. The structure of the LiNbO$\sb3$ films is determined to be a strong function of the substrate temperature. The preferred crystal orientation of the film is found to depend on the substrate orientation. Of particular importance is the observation of LiNbO$\sb3$ polycrystalline films oriented with the c axis of the crystallites normal to the surface of $\langle$111$\rangle$ silicon substrates. This result is important since the ferroelectric polarization and photocurrents are directed along the c axis of crystal, making the development of ferroelectric memory devices using LiNbO$\sb3$ possible. Scanning electron microscopy revealed that the films were generally smooth, and no ferroelectric domain contrast was observed. Ellipsometry was used to determine the refractive indices and thicknesses of the films