Microwave Tunable Capacitor Cv Characteristics Of The Material

(Ba₀.65Sr₀.35)TiO₃ (BST35) and (Ba₀.50Sr₀.50)TiO₃ (BST50) thin films are manufactured by the technology of pulsed laser deposition (PLD), and (Pb₀.72La₀.28)Ti₀.93O₃ (PLT28) thin film prepared is by sol-gel method. Bottom electrodes of CaRuO₃ (CRO) and LaNiO₃ (LNO) buffer-layers are prepared by radio frequency sputtering and PLD, respectively. Using CRO and LNO buffer-layers, BST35/CRO and BST50/LNO heterostructure thin films are prepared. The dielectric properties and tunability of BST35, BST50, BST35/CRO, BST50/LNO and PLT28 thin films are measured, the orientation mechanism of these films, the relation of process conditions, microstructure and properties are discussed. Main results are as follow:1. The highly (100)-oriented BST35 and BST50 thin films on Pt( 111 )/Ti/SiO₂/Si( 100) substrates are prepared by PLD. The BST thin films has a columnar growth characteristic, and the average grain size of BST35 and BST50 thin films are about 50 and 150-200 nm, respectively.The dielectric constant and tunability of BST35 thin film at zero field and 254 kV/cm, are 810 and 76.3%, respectively. Also, The dielectric constant and tunability of BST50 thin film at zero field and 225 kV/cm, are 875 and 58.9%, respectively. The highly dielectric tunability is based on the (100)-oriented columnar-grained thin films and tensile stress, a contraction occurred along the c axis leading to an enhancement of the in-plane oriented polar axis. When higher voltages or electric fields were applied to the (100)-oriented BST thin films, the in-plane orientation of the polar axis resulted in higher tunability.2. The highly (100)- oriented BST35 and BST50 thin films on Pt/Ti/SiO₂/Si substrates and highly (110)-oriented BST35/CRO and BST50/LNO heterostructure thin films on Pt/Ti/SiO₂/Si substrates are prepared by PLD, respectively. The highly (100)-orientation of BST thin films is considered to be self-textured growth, in accordance with minimum surface energy conditions. And on the other hand, a (110) plane is preferred in epitaxial textured growth.It is obvious that the surface morphology of BST35/CRO heterostructure thin film has many cluster grains, and the cluster size is up to 500 nm, which are composed by nano-sized grains in size of about 60 80 nm. The average cluster size of columnar-grained BST50/LNO film is about 200 nm, which also are composed by nano-sized grains in size of about 50-80 nm. It also revealed that a dense, homogenous, uniform microstructure, smooth and pinhole-free surface morphology was obtained in the BST films on Pt/Ti/SiO₂/Si substrates without and with CRO and LNO buffer-layers.The dielectric constant and tunabilities of BST35/CRO and BST50/LNO heterostructure thin films are 851 and 78.1%, 986 and 60.1%, respectively. Compare with single composition BST35 and BST50 thin films, the CRO and LNO bottom electrodes enhanced the dielectric properties and tunabilities. The tunabilities of BST35 and BST35/CRO films are up to 76.3 % and 78.1%, are the best results and reported at the first.3. Nanocrystalline PLT28 thin films on Pt/Ti/SiO2/Si prepared by sol-gel method. A dense, homogenous, uniform microstructure, smooth and pinhole-free surface morphology is obtained in the PLT28 films on Pt/Ti/SiO2/Si substrate, and the average grain size is about 25-30 nm. The dielectric constant and tunability of PLT28 thin films are 1242 and 68.4 %, respectively at zero field and 363 kV/cm.The results as well as BST thin film. We reported the high tunability of PLT28 films at the first.