Gold metal deposition by atomic layer deposition (ALD) was studied. Trimethylphosphinotrimethylgold(III) was synthesized as the chemical precursor. Using just oxygen plasma, the films were discolored and nonmetallic in appearance, typically they were brown or dark purple. These films discolored and delaminated over time in ambient conditions and developed a foul odor. Energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) showed that gold metal was certainly present, but so too were oxygen and phosphorus. In the XPS spectrum, a peak was observed centered at 134.1 eV, which is in the range of the P(V) oxidation state. There was also evidence of Au(0), with peaks at 84.5 and 88.2 eV, and Au(III) at 87.5 and 90.9 eV. This suggests that some of the phosphine ligand from the precursor remained with the gold adatom at the surface, and was converted into a gold-phosphine containing film when reacted with oxygen plasma. XPS analysis of these films showed very clearly that there was only metallic gold no phosphorus signals observed. At five ALD cycles, the particles had a bimodal dispersity, clustered in small and large particles.

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Journal Chemistry of Materials
Griffiths, M.B.E. (Matthew B. E.), Pallister, P.J. (Peter J.), Mandia, D.J. (David J.), & Barry, S.T. (2016). Atomic Layer Deposition of Gold Metal. Chemistry of Materials, 28(1), 44–46. doi:10.1021/acs.chemmater.5b04562