Dielectric properties of crystalline and amorphous transition metal oxides and silicates as potentialhigh-κ candidates: the contribution of density-functional theory

Abstract

A review is given of various first-principles studies of the dielectric properties of crystalline andamorphous transition metal oxides and silicates, which have drawn considerable attention as potentialhigh-κ materials. After a brief summary of the principal equations of density-functional theoryrelated to the dielectric properties of solids, the results obtained for group IVbM = (Hf,Zr,Ti) andIIIb M = (Y,La,Lu) transition metals crystalline oxides and/or silicates are discussed.For the group IVb transition metals, four crystalline phases (cubic, tetragonal, monoclinic and rutile) ofdioxide MO2 with M = (Hf,Zr,Ti) have been considered in the literature. The results of density-functional theory calculationsof the dielectric properties of three crystalline transition metal silicates (hafnonHfSiO4, zirconZrSiO4 and ahypothetical TiSiO4 structure) are also presented. For the group IIIb transition metals,two crystalline phases (cubic and hexagonal) of sesquioxidesM2O3 with M = Lu have been investigated within density-functional theory.Finally, the first-principles results that have been obtained for the amorphous silicates arediscussed. A presentation is given of a scheme recently introduced which relates thedielectric constants to the local bonding of Si and metal atoms. It is based on the definitionof parameters characteristic of the basic structural units centred on Si and metals atomsand including their nearest O neighbours. Applied to amorphous Zr silicates, it provides agood description of the measured dielectric constants, both of the optical and the staticones.