Investigation of linear and non-linear optical features of crystalline and non-crystalline iron oxide thin films for optoelectronic purposes

Abstract

Spray pyrolysis at various temperatures was employed to produce non-crystalline and crystalline iron oxide (α-Fe2O3) thin films on glass. The amorphous and crystalline characteristics of α-Fe2O3 thin films were affirmed via X-ray diffraction analysis. With low deposition times (5 min) and at various substrate temperatures, iron oxide seems almost in a non-crystalline structure. As for the increase in deposition time (40 min), the crystallinity’s degree was enhanced. According to Tauc’s law, the direct gap energy Ed for both the amorphous and the crystalline phases, were found to be 1.95 and 2.125 eV, respectively. Moreover, the indirect gap energy, Ein = 1.65 and 1.71 eV were obtained for the amorphous phases and the crystalline phases, respectively. The linear and non-linear optical features of amorphous and crystalline structure were meticulously and adaptably detailed. It is observed that the behavior of the refractive index n (λ) and extinction coefficient k (λ) of the crystalline state was lower than that of the amorphous state. The real and imaginary linear dielectric constant and also the thin film quality factor were estimated for both the amorphous and crystalline states as well as the volume and surface energy loss functions for the crystalline and amorphous states. In conclusion, amorphous and crystalline α-Fe2O3 nanocrystalline films improved their optical properties, making them potential candidates for multifunctional applications such as optoelectronics and spintronics electronics devices.