Detection of a piezoelectric effect in thin films of thermally grown SiO ₂ via lock-in ellipsometry

We report the observation of structural piezoelectricity in partially ordered thin films of thermally grown silicon dioxide (SiO ₂). The piezoelectric coefficient was determined to be 0.14-0.26 pm/V, and the piezoelectricity was found to originate in a layer with thickness at least 3.5 nm. This value is consistent with literature descriptions of SiO ₂ residual ordering based on structural measurements and modeling. Our observation demonstrates that the residual ordering in thermally grown silicon SiO ₂ is non-centrosymmetric and provides a rare example of diffusion controlled uniaxial growth producing macroscopic piezoelectricity.