Effect of Ni doping on improvement of the tunability and dielectric loss of Ba0.5Sr0.5TiO3 thin films for microwave tunable devices

The structural, microstructural, and surface morphological properties of Ba 0.5Sr0.5TiO3 thin films were investigated as a function of Ni dopant concen tration. The Ni-dopant concentration in BST films has a strong influence on the material properties including dielectric and tunable properties as wel l as film growth rate, Ni doped (less than or equal to3 mol%) BST films sho wed denser, smoother, and smaller grain sizes than those with 6 and 12 mol% Ni. Dielectric constant and loss of 3 mol% Ni-doped BST films were about 9 80 and 0.3%,. respectively. In addition, tunability and figure of merit of 3 mol% doped BST films showed maximum values of approximately 39% and 108, respectively. Correlation of the material properties with dielectric and tu nable properties suggests the the 3 mol% Ni-doped BST films are the optimal choice for tunable device applications.