Structural-optical study of high-dielectric-constant oxide films

High-k polycrystalline Pr2O3 and amorphous LaAlO3 oxide thin films deposited on Si(0 0 1) are studied. The microstructure is investigated using X-ray diffraction and scanning electron microscopy. Optical properties are determined in the 0.75-6.5 eV photon energy range using spectroscopic ellipsometry. The polycrystalline Pr2O3 films have an optical gap of 3.86 eV and a dielectric constant of 16-26, which increases with film thickness. Similarly, very thin amorphous LaAlO3 films have the optical gap of 5.8 eV, and a dielectric constant below 14 which also increases with film thickness. The lower dielectric constant compared to crystalline material is an intrinsic characteristic of amorphous films.