Effect of Stacking Layers on the Microwave Dielectric Properties of (Li_0.5Sm_0.5)TiO₃/CaTiO₃ Thin Films

Abstract

Effect of stacking layers on the microwave dielectric properties of the (Li 0.5 Sm 0.5 )TiO 3 /CaTiO 3 (LSTO/CTO) thin films prepared by the metalorganic solution deposition technique (MOSD) was investigated. The dielectric constant ( K ), dielectric loss (tan δ) and temperature coefficient of dielectric constant ( TCK ) of CaTiO 3 films measured at 6 GHz were 160, 0.003 and -1340 ppm/°C, respectively. In contrast, the (Li 0.5 Sm 0.5 )TiO 3 films showed K of 35, tan δ of 0.001 and TCK of +320 ppm/°C. As the thickness of CTO layer in the LSTO/CTO films increased, K increased and TCK changed from positive values to negative values by dielectric mixing rule. Especially, LSTO(200 nm)/CTO(200 nm) films exhibited TCK of +10 ppm/°C, indicating temperature stability. The tan δ of LSTO/CTO films increased with increasing the thickness of CTO layer. This result was attributed to the fact that the stresses were induced by the higher thermal-expansion coefficient of CTO than that of LSTO. Also, as compared with LSTO(200 nm)/CTO(200 nm) film, the K and TCK of LSTO(100 nm)/CTO(200 nm)/LSTO(100 nm) film were not changed, but the dielectric loss increased. This result indicated that the dielectric loss was affected by the number of interfaces between CTO and LSTO layers.