Piezotronic, ZnO overlaid Bragg grating organic vapors sensors

• Published in: IEEE sensors journal p. 1
• Main Authors: Lopez-Torres, Diego, Aguado, Cesar Elosua, Pappas, Georgios A., Konstantaki, Maria, Klini, Argyro, Lappas, Alexandros, Arregui, Francisco J., Pissadakis, Stavros
• Format: Journal Article
• Language: English
• Published: IEEE 03.05.2023
• Subjects: Piezotronics; Tilted optical fiber Bragg grating sensors; Volatile organic compounds; ZnO
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2023.3270966

We present a ZnO out-cladding, overlaid optical fiber Bragg grating sensor, for the detection of vapors of common alcohols and acetone at concentrations lower than 25ppm, while operating at room temperature. The optical fiber sensing results indicate a chemostriction effect occurring in the ZnO layer when exposed to volatile organic compounds, which effect in turn induces shifts in the cladding, and most importantly, in the core confined, Bragg mode. The sensor exhibits maximum sensitivity of ~1pm/ppm to ethanol vapors, with exposure to other alcohol vapors (isopropanol and methanol) showing lower sensitivities; also, response to acetone vapors was traced at ~0.5pm/ppm. X-ray diffraction measurements of the ZnO nanolayer revealed that, in saturated ethanol vapors atmosphere, the poly-crystalline ZnO film undergoes a contraction by 0.6% of the interplanar distance corresponding to the (002) crystalline direction, denoting the chemostrictive effect through an underlying piezotronic mechanism. X-ray diffraction measurements and optical fiber sensing data are further correlated by numerical simulations carried out, so to study the strain interactions of the ZnO layer with the silica glass optical fiber.