Sol-Gel derived Ferroelectric Thin Films: for Voltage Tunable Applications

Ferroelectric perovskite thin films for voltage tunable applications, namely (Ba,Sr)TiO3 (Barium Strontium Titanate or BST) and (Pb,Sr)TiO3 (Lead Strontium Titanate or PST), are synthesized via the so-called sol-gel route. While BST shows the tendency to severe film cracking, PST can be grown crack free onto platinised Si standard substrates and even directly onto SiO2, SiNx or bare Si. The growth kinetics of PST on platinised SiO2/Si and directly on SiO2/Si are studied in detail using X-ray diffractometry (XRD), scanning electron and atomic force microscopy, SEM and AFM respectively. The dielectric properties, e.g. dielectric constant, loss and tunability of these films were measured. Mn doped PST thin films are grown on Ti/Pt coated SiO2/Si substrates. The surface morphologies, dielectric and tunable properties of these films are investigated as a function of Mn content. It is found that the grain size/roughness, dielectric constant, loss, tunability and figure of merit are affected by the Mn doping level. Further on it is found that the ferroelectricity and the transition temperature between the cubic paraelectric and tetragonal ferroelectric state increase with Mn content.