| Barium strontium titanate (BaxSr1-xTiO3, short for BST) thin films are potential materials for the applications of microwave devices such as dielectric phase shifters and tunable filters due to their high dielectric nonlinearity, low leakage current and adjusting Curie temperature. The microstructures and dielectric properties of BaxSr1-xTiO3 (x=0.45~0.9) ceramics, film thickness uniformity, microstructures and size effect on dielectric nonlinearities of BST films, model for dielectric nonlinearity of ferroelectric films, design and fabrication of phase shifters were investigated. Moreover, there are a series of results as follows:On condition that the center of the substrate is not coincident with that of the target, the magnetron sputtering system was studied. Under the conditions of planetary movement of a substrate underneath a magnetron sputter cathode, a model on the relation between the film thickness and the parameters, such as rotation speed, revolution speed and the distance from target to substrate, was obtained. The relative film thickness distribution can be expressed by T= . It is found that the relative deviation of film thickness distribution is 2.8% within a diameter of φ 100 mm when the ratio of the rotation speed to revolution speed and the distance from target to substrate are 5.3 and 72 mm, respectively.The species and sizes of domains in BST thin films were investigated by piezoresponse force microscopy (PFM). The results show that there are 90° domains. It is found that the critical grain size from a multi-domain to a single-domain is about 31nm.The size effects on nonlinearity of BST thin films were investigated and the results show that the grain size and film thickness play an important role on nonlinearity of ferroelectric films. The dielectric constant and the tunability of BST thin films increase as the grain size and/or film thickness increase. The tunability and the coercive electric field of BST films with mono-domain configuration are...
|
PDF Full Text Request