Preparation And Properties Of Barium Titanate Ferroelectric Thin Films

In recent years, the size of ceramics has achieved their minimum size due to the rapid development of microelectronics integration technology and photoelectron. Thin films are lighter, smaller and easier to be integrated with semiconductor in comparison with the bulk ceramics. Barium strontium titanate (Ba1-xSrxO3) ferroelectirc thin films have been widely applied in dynamic random access memories (DRAMS), dielectric phase shifter and et al because of the high dielectric constant, the low dielectric loss and the low leakage current. BST thin films have been widely researched by numbers of researchers due to it's excellent properties.In this thesis, BST thin films are deposited on Pt/SiO2/Si structured substrates by RF-magnetron sputtering. The target is Ba0.6Sr0.4O3 ceramic. The influence of Oxygen content and sputtering pressure on the growth of thin films is obtained via the analysis of dielectric properties, surface morphology and the result of X-ray diffraction. The ferroelectric properties of BST thin films were researched by Piezoresponse Force Microscope. The research of piezoresponse improved the appropriate test conditions. The following major research results are achieved:1. The grain size of the BST thin films increases due to the additional oxygen while sputtering. The increase of the ratio of oxygen and argon can enlarge the grain size, crystallinity, dielectric constant and dielectric loss. But the growth speed of thin films decreases.2.The crystallinity, dielectric constant and grain size decrease with the increasing of sputtering pressure when the proportion of oxygen and argon remains unchanged. Growth speed of BST film increases at first and then decreases with the increase of sputtering pressure.3.The high frequency test model of Piezoresponse Force Microscope may enlarge the noise and error during the piezoreponse test of BST thin films. We can get clearer and more correct results if using the low frequency test model and keeping the drive amplitude from 2V to 5 V.4. The phenomenon that one grain contains more domains and one domain contains more grains were detected on the surface of BST thin films. The coercive force of the BST thin films in the horizontal direction is much bigger than the coercive force in the vertical direction. The calculated coercive field in the vertical direction is 37.3 kV/cm.