Iron thiobiurets: single-source precursors for iron sulfide thin films.

The iron(III) complexes of several 1,1,5,5-tetraalkyl-2-thiobiurets [Fe(SON(CN(i)Pr(2))(2))(3) (1), Fe(2)(μ-OMe)(2)(SON(CNEt(2))(2))(2) (2), Fe(SON(CNEt(2))(2))(3) (3), and Fe(SON(CNMe(2))(2))(3) (4)] have been synthesized, and the single-crystal X-ray structures of 1, 2, and 4 have been determined. The magnetic properties of complex 2 as a function of the temperature and field were studied. Thermogravimetric analysis of complexes 1-4 showed the decomposition in one major step to iron sulfide residues. All four complexes were used as single-source precursors for the deposition of iron sulfide thin films by aerosol-assisted chemical vapor deposition. Complex 1 gave hexagonal troilite FeS films with a small amount of tetragonal pyrrhotites Fe(1-x)S at 300 °C, whereas only troilite FeS was deposited at 350, 400, or 450 °C. Complexes 2 and 3 deposited a mixture of hexagonal troilite FeS and cubic pyrite FeS(2) films at all temperatures. Complex 4 deposited very thin films of FeS at all temperatures as troilite. Scanning electron microscopy images of the films deposited from all complexes showed that the morphology consisted of plates, granules, rods, and sheets like crystallites. The size and shapes of these crystallites were dependent on the growth temperature and the precursor used. This is the first time that iron(III) thiobiuret complexes have been used as single-source precursors for iron sulfide thin films.