Dielectric properties of MgO-doped compositionally graded multilayer barium strontium titanate films

Abstract

We have grown 5mol% MgO-doped multilayered Ba1−xSrxTiO3 (BST) films having a nominal thickness of 220nm with compositions of each layer as BST60/40, BST75/25, and BST90/10 (upgraded). We also fabricated undoped upgraded BST and uniform BST60/40 films for comparison. Results show that Mg-doping improves dielectric loss (tanδ=0.008) and yields better surface roughness (∼3.1nm) compared to undoped upgraded BST. Mg-doped films displayed excellent temperature stability with temperature coefficient of capacitances of −0.94 and 1.14ppt∕°C from 20to90°C and 20to−10°C, respectively. Mg doping resulted in a moderate dielectric tunability (29%) compared to undoped BST (65.5%) at 444kV∕cm.