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

The effect of strain on the ferroelectricity of HfO _2 thin films after crystallization was investigated by applying uniaxial mechanical strains to Au/HfO _2 /TiN metal–ferroelectric–metal (MFM) capacitors. The remnant polarization (2 P _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 2 P _r after removal of the mechanical strain and the fact that the crystal structure of HfO _2 thin films evaluated by grazing incidence X-ray diffraction measurement was not changed by the tensile strain.