Study of Dielectric Properties of BST Films Preheated Alternately

Normal four-layer-Ba0.6Sr0.4TiO3 (BST) films and two new types of BST films were prepared on Pt/Ti/SiO2/Si substrates by sol-gel method. For the first new type of films composed of four layers, the first layer was preheat-treated (PT) in the preparing process; while for the second new type of films consisted of eight layers, odd layers were alternate-preheat-treated (APT) in the preparing process. The effects of PT and APT on the dielectric properties of the BST films were studied. Scanning electron microscope (SEM) and atomic force microscope (AFM) were used to observe the film surface topography and particulate formation, X-ray photoelectron spectroscope (XPS) was performed to examine the film composition chemical states, and HP4284Aa2type LCR was employed to study the film dielectric properties. It is shown that the normal BST films display bad dielectric properties, whereas the BST films PT are smooth and compact with no crack or shrinkage cavity and significantly reduce surface non-perovskited structure, which indicates obviously the improvement of dielectric properties. Also, the BST films APT are more significantly improved in topographies, made up of nanocrystal grains about 30nm in average size and show more decrease of non-perovskited structure, and reveal lower dielectric loss and more enhanced dielectric stability and strength, satisfying actual application demands in low frequency field. In addition, the effects of annealing temperature and film thickness on the film structure and dielectric properties are discussed.