The pyrolytic LCVD of high-purity gold tracks from alkyl (trialkylphosphine) gold(I) complexes



The pyrolytic LCVD of high-purity gold tracks from the organogold(I) complex MeAuPMe3 is reported. The tracks were deposited onto (100) n-type single-crystal silicon with a thermally grown oxide layer (3000 Å), single-crystal GaAs with an intact native oxide layer and polycrystalline diamond films upon (100) silicon using the output from an argon ion laser (Coherent Innova 100-10) at 514.5 nm. Deposits were grown at a range of scan speeds from 0 to 200 μm s−1 and characterised by SEM, SIMS, LIMA and scanning profilometry. Electrical resistivities as low as 7.04 μΩ cm, within a factor of three of that of bulk gold, were achieved at scan speeds below 156.3 μm s−1. These are consistent with deposit purities of better than 99% (LIMA) without the need for a post-deposition annealing step.

The relationship between power density, beam residence time and deposition rate was measured. The morphology of the deposit from the onset of detectable nucleation through to the formation of continuous tracks was analysed by SEM micrographs of deposits grown at successively increasing power densities. The nucleation process was found to be substrate-dependent. Changes in deposit morphology with power density and scan speed were observed. These include periodicity in track width and at high power densities the development of ‘volcano’-shaped profiles.

The formation of a phosphorus-based interfacial layer, exclusive to laser deposition upon GaAs, is evidence for a reaction between the PMe3 and GaAs.