Unraveling the effect of thickness on the structural, morphological, opto-thermal and DFT calculation of hematite Fe₂O₃ thin films for photo-catalytic application

In this study, hematite Fe₂O₃ thin films with different thicknesses were prepared by a spray pyrolysis process on glass substrates. The crystalline structure and phase formation of obtained films were examined using X-ray diffractometer. Scanning Electron Microscopy and energy dispersive X-ray analysis were carried out to provide surface morphology and elemental composition of the deposits. The geometry characterization of α-Fe₂O₃ was extracted using density functional theory (DFT). Raman spectroscopy measurement depicted the presence of rhombohedral structure of Fe₂O₃. Transmittance spectrum was used to show a decrease of band gap energy as thickness films increased exhibiting a quantum size effect. PL spectrum showed the band to band emission of α-Fe₂O₃ at 578 nm. Thermal properties including static (heat capacity) and dynamic properties (such as thermal conductivity, thermal diffusivity and effusivity) were studied as a function of film's thickness by means of electro-pyroelectric technique. As well as, the percent air included into the studied film has been determined using thermal conductivity measurements. Finally, photocatalytic activity of hematite Fe₂O₃ was tested towards degradation of methylene blue dye solution under solar light illumination for 120 min.