Influence of annealing temperature on the dielectric properties of BaSrTiO3 thin films deposited on various substrates

Abstract

(Ba0.5Sr0.5)TiO3 (BST) thin films were deposited on various substrates, such as LaAlO3(100), MgO(100), R-plane sapphire[1012], and polycrystalline sapphire, by using RF magnetron sputtering to investigate the influence of annealing temperature on the dielectric properties and the tunability of the films. The BST thin films deposited on LaAlO3(100) exhibited a high tunability of 42 % and a low dielectric loss of 0.004 due to the small differences in the lattice parameters and the thermal expansion coefficients between the BST films and the substrates. In contrast, the BST films deposited on a polycrystalline sapphire, exhibiting a relatively high mismatch factor, showed the tunability of therefore similar to 24 % and a dielectric loss of similar to 0.007. The BST thin films on LaAlO3(100), MgO(100), R-plane sapphire[1012], and polycrystalline sapphire were annealed. The optimized annealing temperatures were found to be 950 A degrees C, 1050 A degrees C, 1100 A degrees C, and 1150 A degrees C, respectively. The difference in annealing temperature is likely due to the differences in the lattice parameters and the thermal expansion coefficients between the films and the substrates.