Tb2O3 thin films: An alternative candidate for high-k dielectric applications

We are reporting the growth and structural, optical, and dielectric properties of Tb2O3, a relatively unexplored high-k dielectric material. A pulsed-laser deposition technique was used to grow Tb2O3 thin-films on four different substrates: Si(100), SrTiO3(100), LaAlO3(100), and MgO(100). High resolution X-ray diffraction and transmission electron microscopy results confirmed that film growth in an oxygen-rich (101 Torr) environment yields nearly single-crystal C-phase films, while a low-oxygen (106 Torr) environment growth results in the formation of monoclinic polycrystalline B-phase films. Optical transmission measurements showed that the bandgap of Tb2O3 is direct in nature with a value of 2.8 eV and 3.4 eV for the cubic and monoclinic phases, respectively. By measuring the capacitance of test devices, quite high dielectric constants of 13.5 and 24.9 were obtained for the B- and C-phase Tb2O3 films, respectively.