Crystal structure and dielectric/ferroelectric properties of CSD-derived HfO 2 -ZrO 2 solid solution films

Abstract

Abstract Ultrathin films of HfO 2 -ZrO 2 system, Hf x Zr 1- x O 2 , were fabricated for generating ferroelectric phase. Polycrystalline Hf x Zr 1- x O 2 films were prepared via chemical solution deposition process, in which precursor films consisting of amorphous phase on platinized silicon wafer were crystallized by post-annealing. Metastable orthorhombic phase, recognized as the “ferroelectric” phase, appeared in the Hf x Zr 1- x O 2 films with chemical composition of x = 0.40–0.70 and with film thickness of approximately 40 nm, together with stable monoclinic and/or cubic phases. The dielectric permittivity, e r , and remanent polarization, P r , varied with the chemical composition, meaning that constituent phases of the resulting Hf x Zr 1- x O 2 films dominate their dielectric and ferroelectric properties. Saturated P – E hysteresis loop with P r of 2.1 μC/cm 2 and coercive field of 580 kV/cm was confirmed for the solid solution film of Hf 0.70 Zr 0.30 O 2 ( x = 0.70) at 80 K, whereas no spontaneous polarization was confirmed for pure HfO 2 film ( x = 1.00). These results imply that the orthorhombic phase stabilized by Zr substitution would contribute to the generation of ferroelectricity in HfO 2 -based material consequently.