Optical properties of La-based high-K dielectric films

Abstract

We have characterized thin films of LaScO3 and LaAlO3 which were grown by molecular beam deposition on Si substrates. Samples of LaScO3 were also grown by pulsed laser deposition on MgO substrates. Using transmission studies between 1.5 and 6eV, we have established that low temperature deposition leads to a reduced band gap with respect to the bulk crystal. Furthermore, using spectroscopic ellipsometry from 5to9eV we observe substantial differences in near-band gap absorption between thin and thicker films for both materials. We obtain a band gap of 5.84eV for the thinner film of LaAlO3, whereas we find a band gap of 6.33eV for the thicker film of LaAlO3. Similarly we find band gaps of 5.5 and 5.96eV, respectively, for thin and thick films of LaScO3.