Synergistic Investigation of the Optoelectronic and Morphological Properties of Nanostructured SnO 2 Thin Films: Theoretical and Experimental Correlation via Density Functional Theory Calculations, Microscopy, and Electron Spectroscopy Techniques

This study investigates the impact of substrate temperature and postannealing under ultra‐high vacuum (UHV) on the optoelectronic and morphological properties of SnO 2 thin films deposited at 340 and 380 °C. A correlation between density functional theory calculations and experimental techniques including X‐ray photoelectron spectroscopy (XPS), reflection electron energy loss spectroscopy (REELS), ultraviolet photoelectron spectroscopy (UPS), and atomic force microscopy (AFM) is established. XPS shows Sn 4+ dominates at 340 °C, while Sn 2+ increases at 380 °C. UHV treatment reduces Sn 2+ content and improves stoichiometry by minimizing oxygen deficiencies. UPS confirms a Sn 2+ ‐rich surface at 380 °C, with an increased Fermi level and reduced work function. AFM analysis shows nanostructured films with increased grain size at higher deposition temperatures, while REELS measurements determine energy gaps of 2.80 eV (340 °C) and 3.03 eV (380 °C), consistent with band structure calculations. Kramers‐Kronig analysis of REELS spectra identifies plasmons and electronic transitions, validated by theoretical calculations. Density of states calculations using the modified Becke‐Johnson exchange potential by Tran‐Blaha (TB‐mBJ) highlight the role of O 2 p and Sn orbitals near the Fermi level, correlating with UPS results. Dielectric function analysis further confirms the anisotropic uniaxial nature of SnO 2 . These findings optimize SnO 2 films for applications requiring control of electronic and optical properties.