pH‐sensitive properties of barium strontium titanate (BST) thin films prepared by pulsed laser deposition technique

Abstract pH‐sensitive properties of barium strontium titanate (BST) high‐k thin films as alternative gate material for field‐effect capacitive (bio‐)chemical sensors based on an electrolyte‐insulator‐semiconductor system have been investigated. The BST films of different compositions (Ba0.31Sr0.69TiO3, Ba0.25Sr0.75TiO3and Mg‐doped Ba0.8Sr0.2Mg0.1Ti0.9O3) were deposited by pulsed laser deposition technique from targets fabricated by self‐propagating high‐temperature synthesis. The realised sensors have been electrochemically characterised by means of impedance‐spectroscopy, capacitance–voltage and constant‐capacitance method. The sensors possess a Nernstian‐like pH sensitivity in the concentration range between pH 3 and 11 with a response time of 5–10 s. An equivalent circuit model for the BST‐based capacitive field‐effect sensor is discussed.