Oxygen-free precursor for chemical vapor deposition of gold films: thermal properties and decomposition mechanism

Abstract

Thermal properties of oxygen-, phosphorus-, and halogen-free dimethylgold(III) diethyldithiocarbamate complex (CH 3 ) 2 AuS 2 CN(C 2 H 5 ) 2 (gold, dimethyl(diethylcarbamodithioato -S,S′)-) having excellent storage stability and the mechanism of its decomposition to elemental gold were studied. Saturated vapor pressure was found to be~10 10−1 Torr at 50-90°C. Decomposition of the vapor on the surface starts at T=210°C. The temperature dependence of gas phase composition was studied using the original mass spectrometric technique, it was established that the decomposition of the compound on the surface in vacuum follows three main pathways. Two of them result in the formation of elemental gold, saturated C2-C4 alkanes and (1) protonated ligand or (2) methylated ligand. The third one results in elemental gold and gaseous products: C2-C3 alkylmercaptanes and CH 3 SCN(C 2 H 5 ) 2 . The formation of gold as a sole solid product within the temperature range 210-240°C was confirmed by X-ray photoelectron spectroscopy analysis. It was shown that the compound exhibits the best combination of volatility, thermal, and storage stability among volatile organogold complexes and thus it may be a promising precursor for obtaining gold films by chemical vapor deposition.

Deposition of Au Thin Films and Nanoparticles by MOCVD

“…A good faceting of the crystallites of sample 6 (Fig. 2) could be caused, in our opinion, by the presence of elemental sulfur in the products of thermal decomposition of the precursor 27. The sulfur acts as a surfactant, and thus modifies the surface of growing gold nanocrystals.…”

“…To study the effect of the precursor nature on the structure and morphology of the gold coatings, typical samples deposited under similar conditions (Table 2) were chosen from the entire series of experiments. For these samples, the identical mass transfer of precursor vapor into the reactor was provided by the choice of the evaporator temperature corresponding to the vapor pressure for each compound being equal to 10 −1 Torr (calculated from P / T dependence data) 23, 24, 26, 27. For comparison, we have chosen the deposition temperature of 210°C, which value falls within the investigated range of deposition temperatures for each of the compounds.…”

Chemistry of gold(I, III) complexes with organic ligands as potential MOCVD precursors for fabrication of thin metallic films and nanoparticles

“…Bessonov et al [138,139] have noticed that similar to βdiketonate derivatives, carboxylate complexes have a tendency to increase their volatility on introduction of trifluoromethyl substituents into the ligand. In the series of complexes with salicylaldimine ligands [117], the use of "lighter" [118,141]. In addition, Me 2 AuS 2 CNEt 2 is solid at normal conditions with a low melting point (40-44°C) and transforms to liquid at the conditions of ALD experiment at 99°C which is an additional advantage for its application as an ALD precursor.…”

“…Published work on the direct measurements of vapor pressure dependence on temperature of gold(I, III) complexes with organic ligands are rather sporadic. For Me 2 AuS 2 CNEt 2 the saturated vapor pressure was found to be ~10 −3 -10 −1 Torr within the temperature range of 50-90°C [141]. Griffiths et al [145] have synthesized trimethylphosphinotrimethylgold(III) AuMe 3 PMe 3 which is liquid at room temperature and estimated the enthalpy of sublimation by isothermal thermogravimetry.…”

Aggregation of Au(i)-complexes on amorphous substrates governed by aurophilicity

“…3 Although a number of gold complexes have been suggested for CVD applications, usually gold(III) complexes are used as gold precursors, particularly of the form Me 2 AuX (with X = acetate, dithiophosphinates, pivalate, acetylacetonates, etc.). 2,[4][5][6][7][8] Only a small number of gold(I) complexes have been applied in the past and are mostly of the form L-Au-X (L = phosphine ligands and X = halide, alkyl, carboxylate) but also other gold(I) complexes, e.g. dimeric gold(I) precursors, have been reported.…”