Engineering Nanoscale Polarization at the SrTiO ₃/Ge Interface

Abstract

The ability to manipulate electric polarization at reduced dimension has recently generated intense research interests. Here, we report the engineering of interfacial ferroelectricity by the monolithic integration of a single crystalline SrTiO3 (STO) film on a germanium Ge(001) substrate. A combination of nonlinear optical measurements, microstructural analyses, and phase-field simulations provide evidences of room-temperature ferroelectricity in the epitaxial STO ultrathin film. We show that the collective atomic displacements of Ti near the STO/Ge interface are responsible for the generation of an in-plane ferroelectric polarization. An a1/a2 domain pattern with a stable net polarization along the [110] in-plane direction is revealed.

Keywords: Nanoelectronics, Electric Polarization, Second Harmonics Generation, Interface Ferroelectricity, Phase Field Simulation