Coupled optical–geometric disorder transfer in amorphous oxides

Abstract Amorphous SnOₓ thin films deposited by spray pyrolysis were used as a model disordered oxide system to examine annealing-induced scale-dependent changes within a two-channel optical–geometric interpretive framework combining model-free optical edge-shape metrics with differential-geometric scanning electron microscopy descriptors. Films were deposited on glass at 350 °C and annealed in air at 450 °C for 1 h to probe thermal relaxation in a disordered oxide network. Four complementary probes were employed: ultraviolet–visible spectroscopy to quantify optical-edge broadening directly from measured transmittance and absorbance, energy-dispersive X-ray spectroscopy to track relative compositional changes, field-emission scanning electron microscopy to image micro- and nanostructure, and a differential-geometric formalism that maps microscopy intensity fields into descriptors of interface density, curvature activity, anisotropy, and hierarchical structural organization. Because band-edge fits in highly transparent oxide films on glass can be sensitive to baseline offsets and fitting-window selection, disorder was quantified directly from normalized edge-shape descriptors extracted from the measured optical edge. Annealing sharpened the optical edge, while energy-dispersive X-ray spectroscopy indicated oxygen enrichment together with suppression of the residual chlorine-related signal, consistent with chemical stabilization. In contrast, microscopy-derived descriptors revealed a scale-dependent geometric response: coarse-scale heterogeneity decreased, whereas interface- and curvature-sensitive complexity increased at higher magnifications and anisotropy decreased. Distributional, correlation-length, and spectral analyses, together with patch-level spatial resampling of representative microscopy fields, were consistent with a scale-dependent disorder-redistribution interpretation within the present dataset and provided an internal consistency check under fixed imaging conditions.