Applied Physics Letters 122, 162901 (2023)

https://doi.org/10.1063/5.0142555

Thickness-dependent flexoresistance in SrTiO3 thin films

We report a thickness-dependent flexoresistance effect caused by strain gradient in SrTiO3 (STO) epitaxial thin films. The strain gradient in

STO was induced by using an atomic force microscope diamond-coated tip. The depolarization field caused by the strain gradient changes

the electrical state of the film, resulting in a decrease in the resistance of the films by 4–6 orders of magnitude. By testing the current–voltage

(I–V) curves of STO films with different thicknesses, it is found that the flexoresistance behavior of STO films is obvious thickness dependent:

the thicker the film, the higher the force threshold to trigger the film to enter a highly conductive state. The comparison of the surface

morphology before and after the I–V test with loading shows that only when the thickness of the STO film is below 8 nm, the film can enter

the conductive state from the insulating state without damaging the surface. During the electrical state switching process, the strain gradient

caused by tip loading play an important role in the modification of the film barrier.