Rhodium cyclopentadienyl (1,5-cyclooctadiene) RhCp(1,5-COD) was applied for the growth of Rh films. Rh layers grown in vacuum (0.14–1.4 Pa) were largely contaminated with carbon (~20 mass%C). However, in the presence of H2 during growth reduced the level of carbon to ~3–7 mass% C and lowered the temperature necessary for the deposition from 543 to 503 K (270°C to 230°C).
Rhodium cyclopentadienyl (cyclooctadiene) RhCp(cod) was demonstrated to be a useful precursor for the chemical vapour deposition of Rh layers (and for comparison [RhCp (CO) 2], [[Rh (η-C3H5)(CO) 2], and [Rh (η-C3H5) 3] complexes were used). The obtained Rh films contained carbon impurities wich could be greatly reduced by carrying out the MOCVD process in the presence of H2. The grown Rh layers adhered well to Si substrates. Pyrolysis of [RhCp(cod)] produced a very complex mixture of hydrocarbon products (not fully characterized); the mass spectrum of the residue gave a peak at m/e = 504, corresponding to [Rh3Cp3]+. Pyrolysis appear to produce rhodium clusters at intermediate stages; the added complexity is probably due to the competition between the loss of Cp or cod groups from Rh atom in the initial stage of decomposition.
The
purity of the grown layers [RhCp(cod)] depended on the MOCVD growth temperature: Rh layer deposited at 270°C contained 8% Rh , and 19% C and 0% O as contamination, whereas the layers grown at lowertemperature 230°C consisted of 97% Rh, and only 3%
C and 0% oxygen.[i]
[i] R. Kumar, R.J. Puddephatt, Canad. J. Chem., 1991, New precursors for organometallic chemical vapor deposition of rhodium, http://www.nrcresearchpress.com/doi/abs/10.1139/v91-017