School of Chemistry, University of Southampton, Southampton, SO17 1BJ, UK.
Phys Chem Chem Phys. 2010 Oct 7;12(37):11744-52. doi: 10.1039/c004227g. Epub 2010 Aug 19.
The electrochemistry of [Cu(hfac)(2)], where hfac is hexafluoroacetylacetonate, and Cu(MeCN)(4) were investigated in liquid acetonitrile (MeCN), supercritical CO(2)/MeCN and supercritical trifluoromethane (CHF(3)) at 310-311 K and 17-20 MPa using either [NBu(n)(4)][BF(4)] or [NBu(n)(4)][B{3,5-(CF(3))(2)C(6)H(3)}(4)] as the supporting electrolyte. In liquid acetonitrile it is possible to deposit metallic Cu from both ([Cu(MeCN)(4)][BF(4)]) and [Cu(hfac)(2)] but voltammetry for the [Cu(hfac)(2)] system is more complex and there is evidence of stripping of the Cu by reaction with Cu(ii). Voltammetry of the two copper complexes in scCO(2)/MeCN showed typical plating and stripping features but with slightly increased diffusion limited currents for copper reduction due to the decreased viscosity of the supercritical solvent. In scCO(2)/MeCN the Cu(i) complex, tetrakis(acetonitrile)copper(i) tetrafluoroborate ([Cu(MeCN)(4)][BF(4)]), was found to produce better quality copper deposits than the Cu(ii) complex ([Cu(hfac)(2)]). The Cu(i) complex has the advantages that it is stable and does not undergo comproportionation with copper(0) and that its ligands are totally compatible with the scCO(2)/MeCN solvent system. The solubility of ([Cu(MeCN)(4)][BF(4)]) is limited in scCO(2)/MeCN but can be significantly improved by changing the anion for tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (B{3,5-(CF(3))(2)C(6)H(3)}(4)). It was possible to deposit smooth copper films of high purity and low resistivity (down to 4.0 × 10(-6)Omega cm) from the Cu(i) complex. Copper was also deposited from supercritical CHF(3) using [Cu(hfac)(2)] as a precursor. Although the plating and stripping features in the voltammetry are complicated by the lack of cosolvent and electroreduction of the solvent or free ligands, it was possible to produce copper films with resistivities as low as 5.8 × 10(-6)Omega cm.
研究了电化学 [Cu(hfac)(2)]（其中 hfac 是六氟乙酰丙酮）和 [Cu(MeCN)(4)]（+）在液体乙腈（MeCN）、超临界二氧化碳/MeCN 和超临界三氟甲烷（CHF(3)）中的电化学性质，温度为 310-311 K，压力为 17-20 MPa，使用 [NBu(n)(4)][BF(4)] 或 [NBu(n)(4)][B{3,5-(CF(3))(2)C(6)H(3)}(4)] 作为支持电解质。在液体乙腈中，既可以从 ([Cu(MeCN)(4)][BF(4)]) 也可以从 [Cu(hfac)(2)] 中沉积金属铜，但 [Cu(hfac)(2)] 体系的伏安法更为复杂，并且有证据表明铜通过与 Cu(ii) 反应而被剥离。在 scCO(2)/MeCN 中对两种铜络合物的伏安法研究表明，具有典型的电镀和剥离特征，但由于超临界溶剂的粘度降低，铜还原的扩散限制电流略有增加。在 scCO(2)/MeCN 中，发现四（乙腈）铜（i）四氟硼酸 ([Cu(MeCN)(4)][BF(4)]) 配合物比铜（ii）配合物 ([Cu(hfac)(2)]) 生成的铜沉积物质量更好。Cu(i) 配合物的优点是它稳定且不会与铜（0）发生歧化反应，并且其配体完全与 scCO(2)/MeCN 溶剂系统兼容。在 scCO(2)/MeCN 中，([Cu(MeCN)(4)][BF(4)]) 的溶解度有限，但通过改变四[3,5-双（三氟甲基）苯基]硼酸根 (B{3,5-(CF(3))(2)C(6)H(3)}(4))，其溶解度可以显著提高。从 Cu(i) 配合物可以沉积出高纯低阻（低至 4.0×10(-6)Omega cm）的光滑铜膜。使用 [Cu(hfac)(2)] 作为前体，也可以从超临界 CHF(3) 中沉积铜。尽管由于缺乏共溶剂和溶剂或游离配体的电化学还原，伏安法中的电镀和剥离特征变得复杂，但仍有可能生成电阻低至 5.8×10(-6)Omega cm 的铜膜。
