Investigation of structural and functional properties of doped BaTiO3 thin films for potential application in tunable microwave devices

Abstract

Ferroelectric behavior of perovskites makes these materials very popular for various applications in microelectronics. Barium titanate is one of the most popular representatives of perovskites and probably the most investigated material from these group. Addition of dopants such as strontium and zirconium can change ferroelectric nature of barium titanate. Different concentration of mentioned dopants has huge influence on barium titanate structural and functional properties. Aim of this work was to approach the paraelectric state of barium titanate for potential application in tunable microwave devices such as varactors, phase shifters, etc. Barium strontium titanate (BST) is mainly used for production of tunable devices, but some other materials as barium zirconium titanate (BZT) can be also interesting for investigation. Precursor solutions were made from barium carbonate and tetrabutylorthotitanate, and as sources of Sr2+ and Zr4+ were used strontium acetate and zirconium (IV) oxychloride octahydrate, respectively. Acetic acid and 2-methoxy ethanol were used as solvents. Prepared sols were used for production of multilayered thin films with spin coating method on silicon and platinized (bottom electrode) substrates. After thermal treatment on different temperatures (750, 900, 1000 °C), prepared samples were structurally characterized by X-ray diffraction, Raman spectroscopy and scanning electron microscopy. After structural characterization samples were prepared for functional measurements and gold electrodes were deposited on top. Dielectric properties were measured with LCR meter, up to 1 MHz. We also measured ferroelectric properties.