Structural and dielectric properties of BaTiO₃/SrTiO₃ artificial superlattice on MgO and SrTiO₃ single crystal substrates

BaTiO₃ (BTO)/SrTiO₃ (STO) artificial superlattices were deposited by pulsed laser deposition (PLD) on MgO (100) and SrTiO ₃ (100) single crystal substrates. The stacking periodicity of the superlattice was varied from one unit cell to 125 unit cell thickness. The BTO/STO superlattice has epitaxial layers of BTO and STO with parallel crystallographic orientation to MgO (100) and SrTiO₃ (100) substrates. The BTO and STO layers were strained by the lattice mismatch between the BTO and STO layers. The lattice distortion and correspondingly dielectric constant of the BTO/STO superlattice increased with decreasing the stacking periodicity of the superlattice within the critical thickness (∼ 20 nm or BTO₂₅/STO₂₅ period). The BTO/STO superlattice with a maximum dielectric constant of 1230 was obtained at a stacking periodicity of BTO_{2 unit cell}/STO_{2 unit cell}, which was possible by the control of lattice distortions of BTO and STO layers in the artificial superlattice.