Theoretical stability of polarization in metal/ferroelectric/insulator/semiconductor and related structures

The stability of spontaneous polarization in metal/ferroelectric/insulator/semiconductor and related structures is theoretically studied by considering semiconductivity, i.e., the effect of the finite band-gap width. The theory is based on thermodynamics reported previously by us and is extended in order to also examine the surface relaxation of the spontaneous polarization and the quantum confinement effect and to rigorously treat the electron statistics, the work function of the metal electrode and the multidomain. Basic concepts related to these issues are concisely summarized. The results explain the experimental observations well, at least qualitatively, and resolve the pessimistic predictions drawn from conventional theories.