Low-temperature preparation of ferroelectric Sr2(Ta1-x,Nbx)2O7 thin films by pulsed laser deposition and their application to metal-ferroelectric-insulator-semiconductor-FET

Sr-2(Ta1-xNbx)(2)O-7(STN) ferroelectric thin films have been prepared on SiO2/Si(100) substrates by the pulsed laser deposition (PLD) method. Preferential (110) and (151)-oriented STN thin films were deposited at a low temperature of 600 degreesC in N2O ambient gas at 0.08 Torr. A counterclockwise C-V hysteresis was observed in the metal-ferroelectric-insulator-semiconductor (MFIS) structure using Sr-2(Ta-0.7,Nb-0.3)(2)O-7 on SiO2/Si deposited at 600 degreesC. The memory window in the C-V curve spreads symmetrically towards both positive and negative directions when the applied voltage is increased and the window does not change in sweep rates ranging from 0.1 to 4.0 x 10(3) V/s. The C-V curve of the MFIS structure does not degrade after 10(10) cycles of polarization reversal. The gate retention time is about 3.0 x 10(3) s when the voltage and time of write pulse are +/- 15 V and 1.0 s, respectively, and the hold bias is -0.5 V.