Dielectric Response of Ta[sub 2]O[sub 5], Nb[sub 2]O[sub 5], and NbTaO[sub 5] from First-Principles Investigations

High-κ dielectrics are intensively investigated as a replacement for in integrated nanoelectronics. In particular, for the next generation of dynamic random access memory metal–insulator–metal capacitors, the Ta- and Nb-based oxides are among the most interesting candidates that display a relatively large dielectric constant with a bandgap larger than 3 eV. In this paper, we show that it is possible to modulate the dielectric response of by admixing it with . The dynamical charges and dielectric constants of and for different crystal phases were calculated at the density functional theory level. The averaged dielectric constants range between 27 (38) and 42 (77) for in the hexagonal and orthorhombic varieties. A mixed orthorhombic composition exhibits a directionally averaged dielectric constant of 54, close to the arithmetic mean value of the binary species. The origins of the dielectric permeability are discussed and compared to experimental measurements.