The effects of applied current density and bath concentration on the morphology, crystal structure and optical properties of electrodeposited hematite thin films

Highlights: • As-deposited films are amorphous and need to be heat treated to recrystallize. • High current density (concentrated bath) leads to formation of thick films. • High current density (concentrated bath) leads to obtain fine film morphology. • High current density (concentrated bath) leads to obtain small crystallite size. • High current density (concentrated bath) leads to obtain films with large bandgap. -- Abstract: In this study, hematite thin films were electrodeposited galvanostatically on fluorine doped tin oxide substrates. The effects of the applied current density and bath concentration on the morphology, crystal structure and optical properties of the electrodeposited films were investigated using secondary electron microscopy, X-ray diffraction spectroscopy and UV–visible adsorption spectroscopy techniques. The results showed that the as-deposited films are hexagonal iron oxyhydroxide with very low crystallinity which need to be heat treated to be recrystallized as hematite films while the higher band gap values of the as deposited films, the higher that of the heat treated hematite films would be. Moreover, by increasing the applied current density during the electrodeposition process or using baths containing high amounts of Fe³⁺ ions, hematite films with fine morphology, small crystallite size and high band gap values will be electrodeposited.