Ferroelectric materials have been discovered for one century and widely served in many devices, especially in micro-electro-mechanical systems.With increasingdemands for device miniaturization, the ferroelectricity persisting to nanoscale and below becomes more and more crucial, but remains a challenging scientific question.Although cutting-edge molecular bean epitaxy and pulsed laser deposition techniques can grow thin films down to atomic level, the surface charges from dangling bonds, uncompensated depolarization field, as well as epitaxial substrates, can easily kill their ferroelectricity and lead to the notorious “dead layer”.