Ultrafast Photoinduced Strain in Super-Tetragonal PbTiO3 Ferroelectric Films

The ultrafast photoinduced strain in ferroelectric coupling of piezoelectric and photovoltaic effects have been focused in the last decade, making them extend numerous applications including ultrafast optical memories, sensors and actuators with strain engineering. The mechanism of screening of the depolarization field by photoinduced carriers is generally accepted for ultrafast photoinduced strain in ferroelectric, while the thermal component of the strain is usually diluted as the offset and have not been systematically confronted, leading to unnecessary confusion. Herein, both the positive and negative thermal expansion effect in composite ferroelectric epitaxial films have been investigated by use of high repetition rate ultrafast X-ray diffraction, along with the piezoelectric and photovoltaic effects. The coupling of the positive/negative thermal effects and the piezoelectric/photovoltaic effects in ultrafast strain have been evidenced and regulated. The opposite lattice response due to different thermal effect of the different axial ratio samples have been observed. The maximum ultrafast photoinduced strain is up to 0.24%, comparable to that of conventional ferroelectric. The interaction of thermal and ferroelectric effect in the induced strain could promote the diversified application with the coupling of light, heat and electricity.