Effects of excess bismuth on the electrical properties of Bi 3.15Nd 0.85Ti 3O 12 thin films

Abstract

Neodymium-substituted bismuth titanate (Bi 3.15Nd 0.85Ti 3O 12; BNT) thin films were prepared on Pt/TiO 2/SiO 2/Si substrates by a sol-gel method varying excess Bi content from 0 to 15 %. All the BNT thin films were grown in a polycrystalline state, irrespective of excess Bi content. The intensity of (117) peak increases with increasing excess Bi content, but it attains a maximum value at 12 % excess Bi. Further increase of the excess Bi decreases the (117) peak intensity. The film with 12 % excess Bi shows strongest (117) peak intensity, implying that this film has (117) preferred orientation beneficial to ferroelectric properties. Roughness and average grain size of the BNT thin films increase gradually with increasing excess Bi content up to 15 %. Remnant polarization, leakage current density and fatigue characteristics are also found to be dependent on excess Bi content. A BNT capacitor with 12 % excess Bi shows an almost flat fatigue profile and does not fail until nearly 10 9 cycles and has a remnant polarization (2P r) value of about 42.33 μC/cm 2 at 7 V. Consequently, 12 % excess Bi is thought to be the optimal amount for fabricating BNT thin films with good structural and electrical properties.