Layered ferroelectrics, often referred to as natural superlattices, exhibit functionalities beyond those of the classical ferroelectric perovskite compounds due to their highly anisotropic structure. Unfortunately, the layered architecture has been impeding their growth as single crystalline thin films, and thus their integration into oxide-electronic devices. Here we demonstrate fatigue-free ferroelectric switching in epitaxial Bi5FeTi3O15 thin films. The achievement of twin-free films with sub-unit-cell thickness precision on a lattice-matching NdGaO3 orthorhombic substrate significantly enhances their uniaxial ferroelectric properties. In the ultrathin regime, such films exhibit inplane polarization with a periodic arrangement of ferroelectric domains, which, in conjunction with uniaxial ferroelectric anisotropy, results in nominally charged domain walls. The uniaxial in-plane ferroelectricity and remarkable endurance after 10 10 switching cycles of Aurivillius thin films breaks new ground for alternative device paradigms that are less susceptible to limitations arising from the depolarizing-field effects in the ultrathin regime.

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