Thin films of platinum and of palladium have been prepared successfully by plasma-enhanced chemical vapour deposition, and now the use of this method for the formation of thin rhodium films has been reported (A. Etspüler and H. Suhr, “Deposition of Thin Rhodium Films by Plasma-Enhanced Chemical Vapor Deposition”, Appl. Phys. A., 1989, 48, (4), 373–375).

Dicarbonyl-2,4-pentadionato-rhodium(I) was vapourised from a vessel whose temperature could be changed to achieve the required vapour pressure of the organometallic compound and was then carried into the reaction vessel, through the upper electrode, by a flow of argon or a mixture of argon and hydrogen. The rate of deposition and the properties of the rhodium film depend upon a number of parameters including the temperature of the source, the temperature of the substrate, the partial pressure of the organometallic, and the hydrogen content of the carrier gas.

It was found that a source temperature of 50°C gave the best results; increasing the substrate temperature from 30°C to 150°C increased the rhodium content of the deposit from 86 to 96 per cent and lowered its resistivity by a factor of four. Hydrogen in the carrier gas also resulted in a further increase in the rhodium content of the film. The lowest resistivity value determined for these thin rhodium films was 23μ Ωcm, compared to 4.51μ Ωcm for pure bulk rhodium at a temperature of 20°C.

Plasma-enhanced chemical vapour deposition using organometallic is thus a suitable technique for preparing rhodium thin films, especially on three-dimensional and temperature sensitive substrates.