Dinickel-ditin oktakis(tert-butoxide) [Ni2Sn2(OtBu)8] (a novel Ni−Sn heterometal alkoxide) was synthesized and characterized.
[Ni2Sn2(OtBu)8] was applied as single source precursor for the deposition of thin layers of biphasic composite, Ni3Sn4/SnO2 by CVD at 450−550 °C temperatures. The decomposition
of the precursor [Ni2Sn2(OtBu)8] containing two metal atoms (Ni and Sn) in a single molecule, occurred in the way producing intermetallic Ni3Sn4 grains homogeneously incorporated in an SnO2 matrix. Two simultaneous chemical processes: (i) disproportionation
of Sn(II) species and (ii) redox reactions between Sn(II) and Ni(II) species, were responsible for the formation of Ni3Sn4/SnO2 composite. At temperatures up to 500 °C,the fragmentation of the precursor and
Sn(II) component disproportionation were favored, which resulted in the formation of NiO, Sn(0), and SnO2. At higher temperatures (550 °C) dominated redox reactions leading to the formation of Ni3Sn4 alloy. Such metal alloy−metal oxide composite
Ni3Sn4/SnO2 was homogeneous on a micrometer level (by EDX) on various substrates (steel, copper, silicon wafer). Ni3Sn4 and SnO2 as the only crystalline phases were determined in the layers obtained at 550 °C, according to powder X-ray diffraction measurements.
A microstructured surface with a fibrous morphology was observed by SEM. A bimodal mixture of Ni3Sn4 crystallites (ca. 60−80 nm) uniformly dispersed in a SnO2 matrix (30−45 nm) was found by HRTEM. The biphasic nature of the grown layers (with composition
Ni3Sn4/SnO2) was confirmed by the isomeric shift in the Mössbauer spectra (when compared with the Ni3Sn4 and SnO2 standards). The as-deposited and Ar sputtered films
were studied by ESCA, the elemental composition, oxidation states of Ni and Sn atoms, and the effect of atmospheric oxidation surface metal atoms were determined. [i]
[i] M. Veith, N. Lecerf, S. Mathur, H. Shen, S. Hüfner, Chem. Mater., 1999, 11 (11), pp 3103–3112, DOI: 10.1021/cm991034c, « Incorporation of a Binary Alloy in an Oxide Matrix via Single Source Precursor CVD Process »