Open Access

ARTICLE

Annealing-Induced Structural and Optical Modifications in SnS Thin Films and Their Impact on CO₂ Gas Sensing Performance

Seham Hassan Salman¹, Sarmad Mahdi Ali¹, Hawraa Hadi^2,*, Dhufr Hadi³

1 Department of Physics, College of Education for Pure Science (Ibn-Alhaitham), University of Baghdad, Baghdad, Iraq
2 Department of Anesthesia, College of Health and Medical Techniques/Kufa, Al-Furat Al-Awsat Technical University, Al-Kufa, Iraq
3 Department of Physics, College of Education for Pure Sciences, University of Kerbala, Karbala, Iraq

* Corresponding Authors: Hawraa Hadi. Email: ,

Chalcogenide Letters 2026, 23(5), 3 https://doi.org/10.32604/cl.2026.081302

Received 27 February 2026; Accepted 05 May 2026; Issue published 02 June 2026

Abstract

Films of (SnS) with a thickness of 400 nm were deposited by the thermal evaporation technique to investigate the influence of annealing temperature on their Physics and CO₂ gas-sensing characteristics. The deposited films were annealed at 200, 300, and 400°C. Structural characterization was performed using XRD, and the obtained results revealed that all samples possessed an orthorhombic crystal structure with a preferred orientation (301). The annealing treatment significantly improved the crystallinity of the films and reduced structural defects and lattice strain. Surface morphology investigations were performed using atomic force microscopy (AFM), which revealed noticeable modifications in grain size distribution, surface roughness, and film homogeneity after annealing. Optical characterization was conducted in the range of 300–1100 nm. The optical band gap values were determined using the Tauc method from the (αhν)² versus hν plots and were found to be 1.35, 1.38, 1.62, and 1.40 eV for the as-deposited, 200, 300, and 400°C annealed samples, respectively. Several optical constants, such as the absorption, extinction coefficient, and refractive index, were also evaluated. Furthermore, the CO₂ gas-sensing performance of the SnS thin films was examined at operating temperatures of 50, 100, and 150°C. The results demonstrated that both annealing temperature and operating temperature strongly affected the sensitivity and response behavior of the films. Enhanced sensing performance was attributed to improvements in crystallinity, surface morphology, and charge transport properties induced by annealing. The obtained results suggest that annealed SnS thin films are promising candidates for optical and gas-sensing applications.

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