{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T01:28:10Z","timestamp":1760146090632,"version":"build-2065373602"},"reference-count":41,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2024,10,2]],"date-time":"2024-10-02T00:00:00Z","timestamp":1727827200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Ecosystem Rome Technopole project","award":["ECS00000024"],"award-info":[{"award-number":["ECS00000024"]}]},{"name":"European Union\u2014Next Generation EU","award":["ECS00000024"],"award-info":[{"award-number":["ECS00000024"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The acoustoelectric (AE) effect induced by the absorption of ultraviolet (UV) light at 365 nm in piezoelectric ZnO films was theoretically and experimentally studied. c-ZnO films 4.0 \u00b5m thick were grown by the RF reactive magnetron sputtering technique onto fused silica substrates at 200 \u00b0C. A surface acoustic wave (SAW) delay line was fabricated with two split-finger Al interdigital transducers (IDTs) photolithographically implemented onto the ZnO-free surface to excite and reveal the propagation of the fundamental Rayleigh wave and its third harmonic at about 39 and 104 MHz. A small area of a few square millimeters on the surface of the ZnO layer, in between the two IDTs, was illuminated by UV light at different light power values (from about 10 mW up to 1.2 W) through the back surface of the SiO2 substrate, which is optically transparent. The UV absorption caused a change of the ZnO electrical conductivity, which in turn affected the velocity and insertion loss (IL) of the two waves. It was experimentally observed that the phase velocity of the fundamental and third harmonic waves decreased with an increase in the UV power, while the IL vs. UV power behavior differed at large UV power values: the Rayleigh wave underwent a single peak in attenuation, while its third harmonic underwent a further peak. A two-dimensional finite element study was performed to simulate the waves IL and phase velocity vs. the ZnO electrical conductivity, under the assumption that the ZnO layer conductivity undergoes an in-depth inhomogeneous change according to an exponential decay law, with a penetration depth of 325 nm. The theoretical results predicted single- and double-peak IL behavior for the fundamental and harmonic wave due to volume conductivity changes, as opposed to the AE effect induced by surface conductivity changes for which a single-peak IL behavior is expected. The phenomena predicted by the theoretical models were confirmed by the experimental results.<\/jats:p>","DOI":"10.3390\/s24196399","type":"journal-article","created":{"date-parts":[[2024,10,2]],"date-time":"2024-10-02T06:27:31Z","timestamp":1727850451000},"page":"6399","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Acoustoelectric Effect due to an In-Depth Inhomogeneous Conductivity Change in ZnO\/Fused Silica Substrates"],"prefix":"10.3390","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8363-2972","authenticated-orcid":false,"given":"Cinzia","family":"Caliendo","sequence":"first","affiliation":[{"name":"Institute for Photonics and Nanotechnologies, IFN-CNR, Via del Fosso del Cavaliere 100, 00133 Rome, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4052-0022","authenticated-orcid":false,"given":"Massimiliano","family":"Benetti","sequence":"additional","affiliation":[{"name":"Institute for Microelectronics and Microsystems, IMM-CNR, Via del Fosso del Cavaliere 100, 00133 Rome, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4072-0099","authenticated-orcid":false,"given":"Domenico","family":"Cannat\u00e0","sequence":"additional","affiliation":[{"name":"Institute for Microelectronics and Microsystems, IMM-CNR, Via del Fosso del Cavaliere 100, 00133 Rome, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Farouk","family":"Laidoudi","sequence":"additional","affiliation":[{"name":"Research Center in Industrial Technologies CRTI, P.O. Box 64 Cheraga, Algiers 16014, Algeria"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2024,10,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Ballantine, D.S., Martin, S.J., Ricco, A.J., Frye, G.C., Wohltjen, H., White, R.M., and Zellers, E.T. (1997). Chapter 5\u2014Chemical and Biological Sensors. Acoustic Wave Sensors, Academic Press.","DOI":"10.1016\/B978-012077460-9\/50005-8"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"021001","DOI":"10.1088\/1674-4926\/37\/2\/021001","article-title":"Surface acoustic wave devices for sensor applications","volume":"37","author":"Liu","year":"2016","journal-title":"J. Semicond."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Devkota, J., Ohodnicki, P.R., and Greve, D.W. (2017). SAW Sensors for Chemical Vapors and Gases. 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