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

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