Structural and electrical properties of Ba0.5Sr0.5TiO3 thin films for tunable microwave applications

The primary objective of this research is to optimize the different deposition conditions to obtain high tunability and low dielectric loss of Barium Strontium Titanate (BST) thin films at microwave frequencies. Ba0.5Sr0.5TiO3 thin films were deposited on Pt/TiO2/SiO2/Si substrates by pulsed laser deposition technique (PLD). Deposition conditions like temperature, oxygen pressure, substrate to target distance and laser energy are varied to obtain. the objective. Deposition of the BST thin films on the Pt/TiO2/SiO2/Si substrates was carried out at temperatures of 450degreesC, 550degreesC, 650degreesC and oxygen pressures of 250mTorr and 450mTorr with laser fluence of 250 mJ/cm(2) and 45 OmJ/cm(2) at 10 pulses per second. The microstructural and phase analysis of the deposited BST films at different temperatures and different oxygen pressures were performed using X-ray diffraction (XRD) method. The diffraction patterns are attributed to cubic (perovskite) crystal system. Atomic force microscopy (AFM) was used to perform the surface analysis of the films deposited at different substrate to target distances, varied laser energies and oxygen pressures. The BST capacitor was fabricated using the Coplanar Waveguide Structure and the capacitance and dielectric constant were measured using the Vector Network Analyzer (VNA). Tunability of 3.1:1 and loss tangent of 0.0121 was achieved at 0.4-0.8 GHz.