Memory properties of metal/ferroelectric/semiconductor and metal/ferroelectric/insulator/semiconductor structures using rf sputtered ferroelectric Sr0.8Bi2.5Ta1.2Nb0.8O9 thin films

Off-axis rf magnetron sputtering has been employed to grow Sr0.8Bi2.5Ta1.2Nb0.8O9 (SBTN) ferroelectric thin films with (115) preferred orientation on SiO2/Si and Si substrates. The lower temperature and the higher oxygen mixing ratios [OMR, O2/(Ar+O2)] used in film processing lead to reduction in the leakage current densities and widening the memory window of the resultant metal–ferroelectric–insulator–semiconductor (MFIS) structures. The maximum memory windows of the MFIS structures based on 40% OMR SBTN films deposited at 500 °C on SiO2/Si substrate are 2.87 and 2.27 V at the bias amplitudes of 10 and 8 V, respectively. With increasing applied voltage, the memory window also increases. The memory window decreases from 2.27 to 1.59 V after the 1011 switching cycles at a bias amplitude of 8 V. The capacitance difference, ΔC, between the two states decreases by 48% after retention time of 7000 s.