Nickel Sulfide Thin Films from Thio- and Dithiobiuret Precursors

摘要

The nickel(II) complexes of several 1,1,5,5-tetraalkyl-2-thiobiurets (R = methyl (1); methyl, ethyl (2); ethyl (3); isopropyl (4)) and 1,1,5,5-tetraalkyl-2,4-dithiobiurets (R = methyl (5); methyl, ethyl (6); ethyl (7)) have been synthesized. The single crystal X-ray structures of complexes (1), (3), (4), (6), and (7) have been determined. Thermogravimetric analysis shows all seven complexes decompose in a single step to one or another form of nickel sulfide. The complexes were used as single-source precursors for the deposition of nickel sulfide thin films by aerosol assisted chemical vapor deposition (AACVD) at temperatures between 320 and 480 °C. Complex (1) gave orthorhombic Ni7S6 at all temperatures with spherical tipped wirelike crystallites and plates. Complex (2) gave mixtures of hexagonal Ni_(17)S_(18) and orthorhombic Ni7S6 with wires and plates. Complex (3) also led to a mixture of hexagonal Ni_(17)S_(18) and orthorhombic Ni7S6 phases but with platelike crystallites. In contrast complex (4) gave orthorhombic Ni9S8 with flowerlike structures at 320 and 360 °C and branched structures at 400 °C. Complex (6) gave hexagonal NiS_(1.03) at 360 and 400 °C, and orthorhombic Ni7S6 at 440 and 480 °C with wires and rods composed of spherical particles. Complex (7) gave rods composed of hexagonal plates with hexagonal NiS_(1.03) phase at 360 and 400 °C and orthorhombic Ni7S6 at 440 and 480 °C. The composition of films deposited from all these complexes was confirmed by EDX analysis. The influence of the precursors on the nature of the deposited films is discussed.