Enhanced leakage current performance and conduction mechanisms of Bi1.5Zn1.0Nb1.5O7/Ba0.5Sr0.5TiO3 bilayered thin films

The Bi1.5Zn1.0Nb1.5O7 (BZN)/Ba0.5Sr0.5TiO3 (BST) bilayered films and BST thin films were prepared via radio frequency (RF) magnetron sputtering, and the leakage current behaviors of the films were investigated. Lower leakage currents of BZN/BST bilayered films were achieved compared with that of BST thin films, especially in the high field region. The potential barrier height of top contact is increased by insertion of a BZN layer in between BST and top Pt-electrodes, which might be responsible for the current reduction of BZN/BST under negative biases (positive voltage applied to bottom electrodes). For the case of positive biases, BZN/BST showed a significant increase in the threshold electric field of Poole-Frenkel emission compared with that of BST, resulting in a current decrease in BZN/BST than that in BST. For the BZN/BST bilayered films at 300 K, since the Schottky emission, Fowler-Nordheim tunneling and Poole-Frenkel emission occur in an extremely high electric field, the leakage current is gover...