Polarization-dependent Raman spectra of heteroepitaxial (Ba,Sr)TiO3/MgO thin films -: art. no. 134107

We have studied the concentration dependence of the Raman spectra of heteroepitaxial (Ba1-xSrx)TiO3 (BST) (x=0, 0.15, 0.30, and 0.45) thin films deposited by rf sputtering on (001) MgO substrates. It is found that substitution of Ba by Sr leads to the distortions of the Ti-O bonds and causes the appearance of new bands in the Raman spectra near the bands corresponding to the Ti-O vibrations. The Sr incorporation induces relatively large shifts of the low-frequency Raman peaks attributed to E-TO and A(1 TO) components of the soft mode. The E-TO soft mode in BST films becomes underdamped for xgreater than or equal to0.3 and is very sensitive to the two-dimensional compressive stresses.