Polarization dependent x-ray absorption fine structure measurements performed at the Ti K edge together with x-ray diffraction have been used to study the local structure in SrTiO3 thin films grown epitaxially on Si(001). SrTiO3 layers on Si(001) are found to be unstrained for a thickness of approximately 80 A, a splitting of the Ti-O distance perpendicular to the interface is observed: rTiO = 1.87 +/- 0.02 and rTiO = 2.09 +/- 0.06 , whereas only a single Ti-O distance is observed within the plane of the interface: rTiO = 1.95 +/- 0.01 . These findings indicate a tetragonal plus displacive ferroelectric distortion of the cubic SrTiO3 unit cell in response to the compressive strain imposed on the SrTiO3 layer by the Si substrate. Modification of the Ti K pre-edge features are consistent with these findings.
Citation: Letter to Nature
Pub Type: Journals
eXAFS, ferroelectric, polarization, STO