Ferroelectric technologies have received extensive attention because of their ability to achieve desirable characteristics for tunable microwave applications due to the dependence of dielectric permittivity on the applied electric field. The use of Barium Strontium Titanate films for optical filters has been relatively unknown. An effort is made to study and characterize the properties of Barium Strontium titanate (BST) thin films with stoichiometric configurations of Ba_0.5Sr_0.5TiO ₃, Ba_0.4Sr_0.4TiO₃ and Ba_0.3Sr _0.7TiO₃ deposited using Pulse Laser Deposition (PLD) technique and to design Voltage & Frequency Tunable Optical Filters.

The objective was to characterize the structural, electrical & optical properties of BST thin films and the design & fabrication of Voltage Tunable Optical filters using Indium Tin Oxide (ITO) as electrode metal. A thickness profile analysis was performed using a DekTak Profiliometer. The surface morphology analysis was performed using Atomic Force Microscopy (AFM). Inter-digital capacitors were designed and fabricated using Titanium tungsten (TiW) and Aluminum on p-type silicon wafers. Keithley wafer probe station in conjunction with the LCR meter was used to find the dielectric constant, dielectric losses & tunabilty of BST thin films. The optical filters were designed on microscope glass slides & pre-deposited (8 ohms/square) ITO glass and tested using the UV/VIS/NIR spectrometer & LCR meter.

The results show that BST thin films have good surface morphology & behave as MOS Capacitors. The transmittance profile shows that BST thin films form an excellent source for the design UV blocking filters. The filter analysis reveals that the absorbance and transmittance of BST thin films changes in the presence of an electric field, showing good voltage and frequency dependent tunability.