Dielectric and optical properties of epitaxial rare-earth scandate films and their crystallization behavior

Rare-earth scandates (⁠$ReScO3$⁠, with $Re=Y$⁠, La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, i.e., the entire series for which the individual oxides are chemically stable in contact with Si) were deposited in a temperature-gradient pulsed laser deposition system onto $LaAlO3$ substrates. The crystallization temperature depends monotonically on the Re atomic number and the Goldschmidt tolerance factor, with crystallization temperatures as low as $650°C$ for $LaScO3$ and $PrScO3$⁠. The dielectric constants of the crystalline films $K≈30$ (determined by microwave microscopy) are significantly larger than those of their amorphous counterparts. In combination with the large observed band gaps (⁠$Eg>5.5eV$⁠, determined by ellipsometry), these results indicate the potential of these materials as high-$K$ dielectrics for field-effect transistor applications.