High dielectric permittivity of HfO2-based films with (La,Bi,Nb) substitution

HfO2 thin films with elemental substitutions were formed by chemical solution deposition. Bi substitution distorts the HfO2 lattice and increases the polarization value. (Bi,Nb) substitution compensates the charge balance to prevent the formation of oxygen vacancies. The relative dielectric permittivity of the HfO2 film with 5 mol% La, 5 mol% Bi, and 5 mol% Nb substitution under an applied DC field was observed to be up to 78. The constriction of the polarization-electric field (P-E) curve disappears at a temperature lower than that where the dielectric permittivity is maximum. The phase transition from the paraelectric tetragonal phase to the ferroelectric orthorhombic phase causes the constriction of the P-E curve to disappear. We consider that the high dielectric permittivity was due to the phase-transition-related phenomena. (C) 2018 The Japan Society of Applied Physics