Ferroelectricity in hafnium oxide thin films

We report that crystalline phases with ferroelectric behavior can be formed in thin films of SiO(2) doped hafnium oxide. Films with a thickness of 10 nm and with less than 4 mol. % of SiO(2) crystallize in a monoclinic/tetragonal phase mixture. We observed that the formation of the monoclinic phase is inhibited if crystallization occurs under mechanical encapsulation and an orthorhombic phase is obtained. This phase shows a distinct piezoelectric response, while polarization measurements exhibit a remanent polarization above 10 mu C/cm(2) at a coercive field of 1 MV/cm, suggesting that this phase is ferroelectric. Ferroelectric hafnium oxide is ideally suited for ferroelectric field effect transistors and capacitors due to its excellent compatibility to silicon technology. (C) 2011 American Institute of Physics. [doi:10.1063/1.3634052]