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Ultraviolet-Produced Lead-Free and Composite Nanomaterials for SAW Devices

Yashfeen Khan

We report the specific interaction of various gases on the modified surface of acoustic wave devices for gas sensor applications using the piezoelectric ceramic material BaSrTiO3 (BST) and various Sr concentrations. To increase the sensor’s sensitivity, the conductive polymer polyethylenimine (PEI) was deposited on top of BST thin films. BST thin films were deposited using pulsed laser deposition (PLD), and PEI thin films were deposited using matrix assisted pulsed laser evaporation (MAPLE), which were then integrated into an interdigital Au electrode (IDT) test heterostructure. The layered heterostructures were further integrated into surface acoustic wave (SAW) devices in order to measure the frequency response to a variety of gases, including oxygen, carbon dioxide, and nitrogen. There were differences in the frequency shifts between the sensors when the layered structures of PEI/BST and the frequency responses of sensors based on thin films of the piezoelectric material deposited at various pressures were compared. The results of the SAW tests that were carried out at room temperature were influenced by the conditions of deposition—oxygen pressure and the proportion of strontium in the BatiO3 structure. Frequency shift responses were obtained for each and every one of the gases under investigation at a concentration of Sr x = 0.75. Out of all the ones that were looked at, the BST50 polymer CO2 detection sensor had the best frequency shifts.