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 degrees C for LaScO3 and PrScO3. The dielectric constants of the crystalline films K approximate to 30 (determined by microwave microscopy) are significantly larger than those of their amorphous counterparts. In combination with the large observed band gaps (E-g > 5.5 eV, determined by ellipsometry), these results indicate the potential of these materials as high-K dielectrics for field-effect transistor applications. (c) 2006 American Institute of Physics.