Crystal structure and dielectric/ferroelectric properties of CSD-derived HfO2-ZrO2 solid solution films

Ultrathin films of HfO2-ZrO2 system, HfxZr1-xO2, were fabricated for generating ferroelectric phase. Polycrystalline HfxZr1-xO2 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 HfxZr1-xO2 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, epsilon(r), and remanent polarization, P-r, varied with the chemical composition, meaning that constituent phases of the resulting HfxZr1-xO2 films dominate their dielectric and ferroelectric properties. Saturated P-E hysteresis Mop with P-r of 2.1 mu C/cm(2) and coercive field of 580 kV/cm was confirmed for the solid solution film of HfxZr1-xO2 (x = 0.70) at 80 K, whereas no spontaneous polarization was confirmed for pure HfO2 film (x = 1.00). These results imply that the orthorhombic phase stabilized by Zr substitution would contribute to the generation of ferroelectricity in HfO2-based material consequently.