Characterization of metal-ferroelectric (BiFeO3)-insulator (ZrO2)-silicon capacitors for nonvolatile memory applications

The electric properties of ferroelectric $\mathrm{Bi}\mathrm{Fe}{\mathrm{O}}_3$ (BFO) thin films with $\mathrm{Zr}{\mathrm{O}}_2$ insulating buffer on Si substrates fabricated by chemical solution deposition were investigated. $\mathrm{Zr}{\mathrm{O}}_2$ demonstrates excellent insulating properties on Si substrates. The metal-ferroelectric-insulator-semiconductor (MFIS) structure exhibits clockwise capacitance-voltage hysteresis loops due to the ferroelectric polarization of BFO. The maximum memory windows are 0.66 and $0.78\mathrm{V}$ , respectively, for BFO deposited on postannealed $\mathrm{Zr}{\mathrm{O}}_2$ and on unannealed $\mathrm{Zr}{\mathrm{O}}_2$ insulating layers. The small memory window of the $\mathrm{BFO}∕\mathrm{Zr}{\mathrm{O}}_2$ (postannealed) MFIS is caused by significant interface trap states on the $\mathrm{BFO}∕\mathrm{Zr}{\mathrm{O}}_2$ interface; this is supported by $C\text{-}V$ measurements under varying frequency.