Trends in volatility with changes in the halide ligand were established for gold(I) complexes of the type X-Au-L [X = Cl, Br, I; L = CNBu, CNMe, PMe, P(NMe), P(OCHCF)] by determining the temperatures for the onset of sublimation (T) at a fixed pressure. Within each series of isocyanide complexes, T decreases with increasing atomic radius of the halide, making the iodide complex the most volatile. For the phosphine and phosphoramidate complexes, the chloride and bromide have similar T values with the bromide slightly higher, but the iodide complex is again the most volatile of the three. The trends in volatility can be correlated to variation in Au-Au bond distances and aggregation patterns in the solid state structures. For the P(OCHCF) complexes, melting occurred before sublimation, but the iodide complex was still more volatile than the bromide. These trends have implications for the use of these complexes in electron beam induced deposition and chemical vapor deposition, for which precursor volatility is important.

Abstract

The Au(I) complexes CF 3 AuCNMe (1a) and CF 3 AuCN t Bu (1b) were investigated as Au(I) precursors for focused electron beam-induced deposition (FEBID) of metallic gold. Both 1a and 1b are sufficiently volatile for sublimation at 125 ± 1 mTorr in the temperature range of roughly 40−50 °C. Electron impact mass spectra of 1a−b show gold-containing ions resulting from fragmenting the CF 3 group and the CNR ligand, whereas in negative chemical ionization of 1a−b, the major fragment results from dealkylation of the CNR ligand. Steady-state depositions from 1a in an Auger spectrometer produce deposits with a similar gold content to the commercial precursor Me 2 Au-(acac) (3) deposited under the same conditions, while the gold content from 1b is less. These results enable us to suggest the likely fate of the CF 3 and CNR ligands during FEBID.

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