SiGe nanoribbons as CO and NO gas adsorber: a DFT study

Abstract This paper presents the results of a study on CO and NO adsorption on SiGe nanoribbons, conducted using density functional theory with the VASP quantum simulation program. The results indicate a slight change in the Si-Ge bond length following CO and NO adsorption. While the buckling changes slightly with CO adsorption (approximately 0.034 Å), it shows a significant increase after NO adsorption (0.453 Å). Electronically, the findings demonstrate that CO adsorption widens the band gap, whereas NO adsorption modifies the original structure’s properties from semiconducting to metallic. SiGe nanoribbons exist with a band gap of 0.2484 eV according to GGA-PBE calculation, 0.3412 eV according to HSE06 calculation; after CO adsorption, these values are 0.3412 eV and 0.4199 eV, respectively. The study also reveals relative charge transfer and variations in the intensity of π and σ bonds after adsorption. Optically, CO adsorption leads to changes in the light absorption and reflection properties; light is most strongly absorbed is between 3–4 eV, while light is most strongly reflected in the energy range of 4–5 eV. In contrast, NO adsorption renders the material structure transparent, allowing almost all light to pass through. These changes show that SiGe nanoribbons are suitable for CO and NO gas sensors; especially for NO, with a sensitivity when adsorbing NO gas up to almost 100%.