Study of La doped ZnO thin films properties made by spray pyrolysis for gas sensors applications

M. Manica 1,2 , I. V. Tudose 3 , P. Pascariu 1,4 , C. Romanitan 1 , O. Brincoveanu 1 , C. Pachiu 1 , R. Gavrila 1 , S. Antohe 2 , E.
Koudoumas 1,3 and M.P. Suchea 1,3*

1 National Institute for Research and Development in Microtechnologies (IMT-Bucharest), Bucharest 023573, Romania
2 University of Bucharest, Faculty of Physics, 077125, Magurele, Romania
3 Center of Materials Technology and Photonics, Hellenic Mediterranean University, Heraklion 71410, Greece;
4 ”Petru Poni” Institute of Macromolecular Chemistry, Aleea Grigore Ghica Voda, 41A, Iaşi 700487, Romania



In recent years, various studies have been carried out to improve sensors monitoring the state of the environment. There is a lot of emphasis on improving the quality of environmental factors, such as water, air, and soil which are certainly of great importance. In this sense, gas sensors have a crucial importance in detecting and monitoring the amount of pollutants in the environment.

In the recent years, some of the most studied materials for gas sensors fabrication are transparent conductive oxides (TCO) doped with rare earths (RE), because they have a reasonable cost and can be obtained by different deposition techniques that allows their integration in wearables, windows, and other transparent objects. Gas sensors based on La doped zinc oxide (ZnO) have been obtained and successfully tested for acetone and carbon dioxide (CO 2 ) [1,2,3]. Sensing is strongly dependent of TCO thin film morphological and surface properties, that cand be tailored via fabrication conditions. This work focuses on a work that studied the properties of thin films of La doped ZnO with different concentrations of dopant (0.1%, 0.5% and 1%) for applications in gas sensors. The films were obtained by the spray pyrolysis technique. After deposition, the films underwent a thermal treatment, after which the structural and optical properties were studied by X-ray diffraction (XRD), scanning electron micrography (SEM), atomic force microscopy (AFM) and UV-Vis spectroscopy. It was observed that the increase in the concentration of the dopant material determines a considerable variation of the crystallite sizes determined by the Scherrer and Williams Hall methods. A high optical transparency of 60–90% in the visible range of the electromagnetic spectrum was also observed. The structural and electrical properties can be varied and controlled by doping the oxide with different metals and at different concentrations, depending on the desired properties.

Acknowledgments IMT contribution was partially financed by the Romanian Ministry of Research, Innovation and
Digitization through “μNanoEl,” Cod: 23 07 core Programme and partially supported by PNRR/2022/C9/MCID/I8
CF23/14 11 2022 contract 760101/23.05.2023 financed by the Ministry of Research, Innovation and Digitalization
in “Development of a program to attract highly specialized human resources from abroad in research, development,
and innovation activities” within the – PNRR-IIIC9-2022 - I8 PNRR/2022/Component 9/investment 8.

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sensitivity La-doped ZnO sensors for CO2 gas detection at room temperature. Scientific Reports, 13(1), 18398.
[2] Xu, X. L., Chen, Y., Ma, S. Y., Li, W. Q., & Mao, Y. Z. (2015). Excellent acetone sensor of La-doped ZnO
nanofibers with unique bead-like structures. Sensors and Actuators B: Chemical, 213, 222-233.
[3] Chandak, V. S., Kumbhar, M. B., & Kulal, P. M. (2024). Highly sensitive and selective acetone gas sensor-based
La-doped ZnO nanostructured thin film. Materials Letters, 357, 135747.

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