Facile Ferroelectric Phase Transition Driven by Si Doping in HfO 2

The recently discovered ferroelectricity in thin-film orthorhombic HfO 2, which can be directly integrated into complementary metal–oxide semiconductor technology, has become an important research target. However, the use of orthorhombic HfO 2 in practical devices has been limited by undesirable mixing with the monoclinic phase, which is nonpolar and thus degrades the ferroelectric properties. Here, we demonstrate that a Si dopant significantly stabilizes the ferroelectric phase because of its unique bonding characteristics, particularly its intrinsic tendency to form strong covalent bonds with O, thereby weakening the phase boundary to stabilize the ferroelectric orthorhombic phase over the nonpolar monoclinic phase, relatively. On the basis of our theoretical predictions, we conducted transmission electron microscopy measurements and confirmed that Si substitution doping indeed induced…