Thickness dependence of electrical and piezoelectric properties of ferroelectric Ba0.8Sr0.2TiO3 thin films

Ba0.8Sr0.2TiO3 (BST 80/20) thin films with various thickness between 150 nm to 550 nm were fabricated by high-frequency reactive sputtering of a ceramic target in an oxygen atmosphere on p- and n-type Si substrates. Memory windows and effective dielectric constant of the BST film in Au/BST/Si thin film capacitors are found to be increased with the increasing thickness of the film. Surface morphology, ferroelectric domain structure, switching properties and ferroelectric activity of the BST 80/20 thin films have been investigated with the use of piezoresponse force microscopy. Complete domain switching and strong piezoresponse are found in the ferroelectric BST film. The piezoelectric coefficient (d33eff) and the remnant piezoelectric response (ΔPR) of BST 80/20 films are found to be increased with the thickness of the film. The conductivity type of the silicon substrate does not contribute significantly to piezoelectric and electrical properties of BST 80/20 thin films.