Standardized extraction of optical band gap and urbach energy in zno and al-doped zno thin films from uv–vis spectra: an in-silico workflow
DOI:
https://doi.org/10.54355/tbusphys/4.1.2026.0045Keywords:
ZnO thin films, Al-doped ZnO (AZO), optical band gap, urbach energy, UV–Vis spectroscopyAbstract
This study develops and validates a reproducible computational workflow for extracting the optical band gap and Urbach tail parameters of ZnO and Al-doped ZnO thin films from UV–Vis spectra. Synthetic transmission datasets were generated for ZnO and ZnO:Al (0–3 at.% Al) using a physically consistent thin-film optics model with realistic spectral broadening and noise, followed by standardized post-processing to reconstruct absorption behavior and perform band-edge analysis. The optical band gap values derived from the band-edge region remained tightly clustered across all compositions, with group means near 3.31–3.33 eV and small between-replicate dispersion (standard deviation ≤ 0.005 eV), indicating robust gap extraction under a fixed regression protocol. In contrast, the Urbach energy exhibited substantially higher variability, with group means spanning approximately 37–112 meV and larger scatter, highlighting the greater sensitivity of sub-gap analysis to low-signal regions and fitting-window selection. Overall, the results demonstrate that band-gap estimation is comparatively stable when procedures are standardized, whereas Urbach-tail quantification requires stricter control of noise floor and objective windowing. The proposed workflow provides a transparent baseline for consistent reporting and can be directly transferred to experimental ZnO/AZO datasets; the main limitation is that the present results are derived from synthetic spectra, motivating future validation on measured thin-film optical data.
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Copyright (c) 2026 Do-Yoon Lee, Gye-Tai Park
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