The structural, morphological, and optical study of chemical bath deposition and a spin coating deposited mackinawite FeS thin films

The FeS thin films are deposited by chemical bath deposition (CBD) and spin coating deposition. The iron nitrate nonahydrate and sodium thiosulfate pentahydrate are employed as precursor chemicals for Fe and S ions, respectively. The CBD thin film thickness is found to be optimum for deposition time of 120 min and pH of 2.5. Similarly, in case of spin coating deposition, the film deposition is found optimum at rotation speed of 2000 rpm and 20 s deposition time. The analysis for chemical composition of the thin films showed them to be near stoichiometric. The structural analysis showed the thin films to possess tetragonal unit cell structure having mackinawite FeS phase. The crystallite size determined by Scherrer's and Hall-Williamson relation showed it to be larger in case of CBD compared to spin coating deposition. The surface morphology of the deposited thin films showed them to be uniform. The indices assigned to electron diffraction rings of both the thin films matched to X-ray diffraction planes. The optical study showed both the thin films possess direct bandgap having values of 1.75 eV for CBD and 1.81 eV for spin coating deposited thin films. The refractive index variation with wavelength showed both the films have good stability making them suitable for visible range optical applications. The photoluminescence study of the thin films showed them to possess single peaks arising due to near band edge emission by excitons recombination.

Automated summary

FeS thin films were deposited using chemical bath deposition (CBD) and spin coating deposition methods. The films showed stoichiometric composition and possess a tetragonal structure. CBD deposition resulted in larger crystallite size compared to spin coating deposition. The films exhibited uniform surface morphology and direct bandgap, suitable for optical applications in the visible range.