Shape-controlled aerosol-assisted chemical vapour deposition of iron sulfide thin films using heterocyclic iron(II) dithiocarbamates as single-source molecular precursors

Iron sulfide (FeS) thin films are promising materials for renewable energy technologies due to their low toxicity, cost-effectiveness, and tunable optoelectronic properties. However, achieving phase-pure FeS with controlled morphology remains challenging. In the present study, the fabrication of iron sulfide films via aerosol-assisted chemical vapor deposition (AACVD) of bis -(piperidinedithiocarbamato)iron(II) ( 1 ) and bis -(tetrahydroquinolinedithiocarbamato)iron(II) ( 2 ) complexes as single-source molecular precursors is reported. Unlike previous studies which predominantly focused on Fe(III)-based precursors, this work demonstrates the unexplored potential of Fe(II) precursors in tailoring phase purity, crystallinity, and morphology of the iron sulfide thin films. Thermogravimetric analysis confirmed clean precursor decomposition, yielding FeS residues. The deposition of iron sulfide films were carried at temperatures of 350 °C and 450 °C using chloroform solution of precursors, and the resulting films were characterized for structural, optical, and morphological properties. Films deposited using precursor ( 1 ) at 350 °C displayed uniform spherical particles ranging from 240 nm to 370 nm and a direct band gap of 2.29 eV while those at 450 °C revealed anisotropic growth (650 – 1050 nm) and a reduced band gap of 2.19 eV, attributed to quantum confinement effects. Besides, films obtained from precursor ( 2 ) produced the films in the range of 248 – 364 nm for 350 °C and larger sizes in the range of 1.1 – 1.6 µm for 450 °C deposition temperatures. X-ray diffraction confirmed hexagonal Fe₀.₉₇₅S phase formation, with improved crystallinity at higher temperatures. Atomic force microscopy revealed smoother surfaces for films derived from the piperidine-based precursor. These findings establish Fe(II) dithiocarbamates as promising precursors for controlled FeS thin film synthesis and provide a tunable route for tailoring optoelectronic properties for photovoltaic technologies. • Heterocyclic iron(II) dithiocarbamates precursors were used to deposit iron sulfide (Fe₀.₉₇₅S) thin films by AACVD method. • Deposition temperatures controlled particle morphology, transitioning from uniform spherical structures to anisotropic structures. • The study demonstrated that the optical band gap is temperature-dependent as a result of the quantum confinement phenomenon.