  We demonstrate the feasibility of multilevel recording in
Pt/Bi(1-d)FeO3/SrRuO3 capacitors using the ferroelectric resistive switching
phenomenon exhibited by the Pt/Bi(1-d)FeO3 interface. A tunable population of
up and down ferroelectric domains able to modulate the Schottky barrier height
at the Pt/Bi(1-d)FeO3 interface can be achieved by means of either a collection
of SET/RESET voltages or current compliances. This programming scheme gives
rise to well defined resistance states, which form the basis for a multilevel
storage nonvolatile memory.
