Electrically Programmable Bistable Capacitor for High-Frequency Applications Based on Charge Storage at the (Ba,Sr)TiO3/Al2O3 Interface

Hysteresis is induced in paraelectric (Ba,Sr)TiO3 (BST) thin-film capacitors by inserting an Al2O3 barrier layer of a few nanometers in thickness between the BST layer and the electrode. The observed hysteresis is explained by ambipolar charge carrier injection through the Al2O3 layer and charge storage at the BST/Al2O3 interface. The magnitude of the hysteresis can be directly adjusted by manipulating the thickness ratio between BST and Al2O3. Taking into account the low loss of (Ba,Sr)TiO3 capacitors, the observed switching and retention characteristics are suitable for application as non-volatile programmable high-frequency devices, e.g., in radio-frequency identification.