Structural, Electrical and Optical Properties of BaTiO$_{3}$(BT)/Ba$_{(1-x)}$Sr$_{x}$TiO$_{3}$(BST) and SrTiO$_{3}$(ST)/BST Superlattices

Superlattices (SL) have attracted interests due to the possibility of producing superior and new properties compared to the parent constituents. We have fabricated SL of BT/BST and ST/BST with x= 0 - 1 by pulse laser deposition. The films modulation period ($\Lambda )$ in all SL were $\Lambda $= 80 {\AA}, that is, BT$_{\Lambda /2 }$or ST$_{\Lambda /2 }$/BST$_{\Lambda /2 }$and the total thickness of each SL film was $\sim $600 nm. XRD revealed (00l) perovskite structure and the so-called satellite peaks typical of modulated structures. The angular distance ($\theta _{n})$ between the satellite peaks for BT/BST (ST/BST) increases (decrease) with increase (decrease) of x concentration. The polarized Raman spectra of BT/BST SL at room temperature are very close to those of BT; however the activation of folded acoustic phonons in SL was observed when the $\theta _{n}$ increase (BT/ST, BT/BST$_{x=0.7})$. The BT/BST$_{x=0.7 }$showed well defined ferroelectric loop ($\sim $10 $\mu $C/cm$^{2})$, and the dielectric constant and loss values at 10 kHz was 350 and 0.05 respectively. Temperature dependent Raman studies will be discussed.