Narrow Results

We have systematically studied the composition dependence of the dielectric properties of Zr_1-xAl_xO_2-x/2 and Zr_1-xSi_xO₂. An essentially linear variation of the static dielectric constant, ε_s, was observed as a function of composition, x, for compositions rich in the p-block element, i.e., x > 0.4, for both chemical systems. However an abrupt change in ε_s is found near x ≈ 0.35, associated with the onset of crystallinity in as-deposited films. Breakdown fields do not show a comparable composition dependence. Measurements of the index of refraction at optical frequencies, combined with a simple Clausius–Mossotti interpretation, indicates that low-frequency (ionic) contributions to the polarizability exhibit systematic deviation with respect to values linearly interpolated from the endmembers. These trends are not consistently affected by the presence of crystalline order, but are related to changes associated with heterogeneous local oxygen coordination and bonding.

We report the unexpectedly excellent dielectric properties of amorphous thin films with compositions in the Bi–Ti–O system. Films were deposited by RF magnetron reactive co-sputtering. In the composition range of 0.5 < $x$ < 0.7, amorphous ${{\text{Bi}}_{1-}}_x$${\text{Ti}}_x$${\text{O}}_y$ exhibits excellent dielectric properties, with a high dielectric constant, ${𝜀}_r$$\sim$ 53, and a dissipation factor as low as tan $\delta$ = 0.007. The corresponding maximum breakdown field reaches $\sim$1.6 MV/cm, yielding a maximum stored charge per unit area of up to 8 $\mu$C/cm². This work demonstrates the potential of amorphous Bi–Ti–O as a high-performance thin-film dielectric material that is compatible with high-performance integrated circuits.