Preparation and dielectric properties of compositionally graded (Ba,Sr)TiO3 thin film by sol-gel technique
(1.湖北省武汉市湖北大学物理与电子技术学院2.湖南省长沙市中南大学数字科学与计算技术学院3.Department of Materials Science and Engineering, Hubei University, Wuhan 430062, China)
Abstract: Compositional graded BaxSr1？xTiO3 (x=0.6, 0.7, 0.8, 0.9, 1.0) (BST) thin films (less than 400 nm) were fabricated on Si and Pt/Ti/SiO2/Si substrates by sol-gel technique. A special heating treatment was employed to form the uniform composition gradients at 700 ℃. The microstructures of the films were studied by means of X-ray diffraction, atomic force microscope and field emission scanning electron microscopy. The results show that the films have uniform and crack-free surface morphology with perovskite structure phase. The small signal dielectric constant (εr) and dielectric loss (tan δ) are found to be 335 and 0.045 at room temperature and 200 kHz. The dielectric properties change significantly with applied dc bias, and the graded thin film show high tunability of 42.3% at an applied field of 250 kV/cm. All the results indicate that the graded BST thin films prepared by sol-gel technique have a promising candidate for microelectronic device.
Key words: compositional gradient; sol-gel technique; microstructure; dielectric constant; tunability