Enhancement of remnant polarization in ferroelectric HfO2 thin films induced by mechanical uniaxial tensile strain after the crystallization process

Abstract

The effect of strain on the ferroelectricity of HfO2 thin films after crystallization was investigated by applying uniaxial mechanical strains to Au/HfO2/TiN metal–ferroelectric–metal (MFM) capacitors. The remnant polarization (2P r) of MFM capacitors increased when tensile strain was applied during polarization switching. This phenomenon should not be attributed to phase transformation from the non-ferroelectric to the ferroelectric phase, taking account of the fast relaxation of 2P r after removal of the mechanical strain and the fact that the crystal structure of HfO2 thin films evaluated by grazing incidence X-ray diffraction measurement was not changed by the tensile strain.