| Uncooled focal plane array (UFPA) is one device that can work at room temperature. It has attracted much attention for wide application with special properties. This device requires ferroelectric thin films prepared at low temperature. Among these materials, the properties of BST thin films are excellent. The Currie temperature of BST can be regulated by controlling Ba/Sr ratio and be adjusted to the room temperature. To adapt the requirement of UFPA, this essay mainly studied the BST thin films and its properties. There are many methods to prepare BST thin films. Sol-Gel method was chosen because of its advantages. This essay discussed the conditions that affect the stability of BST-sol. Barium acetic, strontium acetic and tetrabutyl titanate were used as raw materials. The temperature of reaction was between 50~70℃,and the ratio of water was less than 5%. BST-sol was got stable and clarity. BST-sol was coated on Pt/Ti/SiO2/Si substrates. Proper spin-coating process was optimized. Spin-coating speed and time were 6000r/min and 30min. After spin-coating, annealing step was studied. Optimal annealing temperature was 600~650℃and the time was 30min. XRD,AFM,XPS analysis methods ware used to analyze properties of BST thin films. The surface of BST thin films were smooth. Dielectric constant of BST thin film was among 270~330, dielectric loss was 2.5~4.5%. Currie temperature was about 40℃and TCD was less than 0.5%. Lanthanum and stannum doped into BST thin films. The influence of dopants on the properties of BST had been studied. Comparing the properties of BST, La-doped BST, Sn-doped BST and BSTSn/BLaST/BSTSn thin films, the dielectric constant and dielectric loss of Sn-doped BST were obviously decreased. The value of dielectric constant and dielectric loss were not basically changed with frequency increases. Dielectric constant and dielectric loss were 140~170, 1.5~2.7% respectively. Currie temperature of BSTSn/BLaST/BSTSn film is about 28℃, and dielectric constant... |
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