Mechanistic Role of H2O and the Ligand in the Chemical Vapor Deposition of Cu, Cu2O, CuO, and Cu3N from Bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)copper(II)

Abstract

The mechanism of chemical vapor deposition of Cu, CU2O, CuO, and CU3N from Cu(hfacac)2-(H2O) was studied by XRD, MS, FTIR, XPS, SIMS, and NMR techniques. The molecular structure of the precursor was established by a single-crystal X-ray diffraction experiment.Crystallographic data (-165 °C): triclinic space group PI, a = 9.402(3) k,b = 11.068(3) A, c = 7.958(2) A, a = 105.71(2)°, 0 = 100.99(2)°, y = 76.27(2)°, V = 767.31 A* 123 45678, Z = 2, R = 0.0303, i?w = 0.0312. In the presence of excess water in the process gas stream, a facile release of free Hhfacac ligand from the copper complex is activated by a proton transfer from coordinated water. Ligand-mediated reduction of the metal from Cu2+ to Cu+ and from Cu+ to Cu°oxidation states occurs in the absence of an external reducing agent at temperatures of 280 and 400 °C, respectively. Evidence for this ligand-mediated reduction is seen in the presence of the two major ligand-oxidation products (CF3COOH and CFsC(OH)2-CH(OH)2) in the effluent from the deposition reaction. A labeling experiment using H2180 proved that oxygen in copper oxide films deposited from Cu(hfacac)2 onto insulating substrates is derived from water and not the hfacac ligand. As an example of benefits that can be derived from this mechanistic knowledge, we have also shown that replacing H2O with NH3 leads to the formation of CU3N.

Synthesis and Characterisation of the First Oxazoline Coordination Compounds Containing the Cu(F6acac)2 Unit: X-ray Diffraction Studies of Cu(kappa2-O,O'-F6acac)2(kappa1-N-Meox) and Cu(kappa2-O,O'-F6acac)2(kappa1-N-Etox)

“…[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][33][34][35] As expected, the complexes reported herein contain chelating κ 2 -O,O'-bonded F 6 acac formally anionic groups with Cu-O bond lengths which are of the typical range (1.9-2.2 Å). The oxazoline ligand, predictably N-bonded, 4,5,[7][8][9][10][11][12]31 occupies a basal position with one of the F 6 acac O-atoms occupying the formal equatorial position of an idealised square pyramidal ligand arrangement.…”

“…This copper containing starting material has been extensively studied in coordination chemistry and materials science due to its ability to coordinate a variety of N-donor ligands which includes organic radicals, heterocycles, primary amines, etc. A wide variety of structural bonding motifs [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] have been observed in the resulting coordination compounds. …”

CVD of Copper(I) Nitride

“…[21] Only two papers on CVD of Cu 3 N have been reported. [22,23] Pinkas et al investigated the proton transfer from a coordinated water molecule to the hfac ligand. [22] As an additional test they used ammonia as a protonating agent and found that the proton transfer from NH 3 to the hfac ligands promoted their removal in a manner similar to H 2 O. Cu 2þ was reduced to Cu þ yielding Cu 3 N. This at a temperature of 400 8C; at 450 8C a mixture of Cu 3 N and Cu was formed.…”

How Does CuII Convert into CuI? An Unexpected Ring‐Mediated Single‐Electron Reduction

“…As we expect this feature to be common to copper(II) molecular species with hydrogen-containing and proton-accepting ligands, this study provides a rationale for the observed and unexpected Cu reduction that takes place in the bottom-up syntheses of copper oxides, [13][14][15] where very high temperatures (> 700 K) are needed to promote the obtainment of copper(II) oxides over copper(I) species under oxidizing conditions. [13] Nevertheless, further investigations on the actual molecule-tonanostructure production process is required; this is actually in progress in our laboratories.…”

“…For example, the formation of copper(I) species from copper(II) sources in the absence of any explicit reducing agent-observed in many experiments and, in some cases, even under oxidizing conditions-has been an intriguing chemical enigma since the early ages of bottom-up technologies. [11,13,14,15] In spite of many progresses, the evolution of the copper oxidation state from the precursor to the material is still a matter of speculation and the strange case of copper reduction without reductants, a missing piece in the basic chemistry of this element, still remains an open and intriguing challenge. The observation of this surprising phenomenon, detected in several fabrication approaches under different conditions, suggests that the origin should lie in the molecular copper sources themselves.…”