Texturing of nanocoatings for surface acoustic wave-based sensors for volatile organic compounds

Abstract

Abstract An approach for texturing of gas-sensitive nanocoatings by using surface acoustic waves (SAW) is presented in this article. The objective of the work is to enhance the performance of precise SAW-based gas sensors due to the increased specific area of the sensitive nanocoating, induced during its growth and to replace the expensive lithographic techniques for nanopatterning, typically used for this purpose. The technique can be used for tuneable alignment of nanoparticles or nanowires and it is scale-independent. To control the texture of the sensitive nanocoating, a specific electrode topology was used to generate waves with a specific space distribution, which in turn caused assembling of the nanoparticles increasing the adsorption capacity. In this way, a broader dynamic range of 7,000 ppm was achieved (three times extended as compared to the non-textured sensing film), measurement error of 0.6% against 4% for the non-patterned, faster response time in the sub-seconds range (970 ms vs 1.1 s), negligible hysteresis of 10 mV (against >100 mV), and very good sensitivity of 5 µV per ppm, which are in line with the current standards for ethanol sensors. The enhanced sensor parameters were achieved by implementation of conventional patterning technologies without the need for nanolithographic techniques for the texturing the nanocoating. The method is low-cost, and applicable in a variety of sensing structures despite the sensing coating (optical, biological, etc.).