DFT Simulation of XPS Reveals Cu/Epoxy Polymer Interfacial Bonding

Abstract

Experiments and computations are performed to assess the interfacial bonding between Cu and a poly-epoxy surface relevant to many applications. The surface of the poly-epoxy is characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy before and after ultrahigh vacuum Cu deposition. Modifications of the XPS spectra are observed, suggesting a strong interaction between specific C and O atoms of the surface with Cu. Density functional theory (DFT) calculations are then performed to simulate XPS spectra and to better understand bonding. DFT computations are performed in the framework of the uGTS methodology, which takes initial and final state effects into account, and allows to calculate chemical shifts between the different C 1s and O 1s molecular orbitals with good accuracy, for the pristine surface. DFT calculations are then set to determine the preferential adsorption sites of Cu on different sites of the polymer surface. Finally, XPS simulation of the C 1s and O 1s spectra with Cu adsorbed at these sites matches very well with the experimental spectra, indicating that Cu atoms interact preferentially with hydroxyls to form Cu−O−C bonds, stabilized by a transfer of 0.5 electrons from Cu to O; hence, Cu is partially oxidized.

Chemical Interactions at the Al/Poly-Epoxy Interface Rationalized by DFT Calculations and a Comparative XPS Analysis

“…For Al interaction with C phenyl , average Al−C phenyl distance for the Al/D (site = C ph ) model is 2.557 Å and the previously reported value using ab initio HF is 2.06 Å. 66 In the case of the Cu/poly epoxy interface, 20 avg. Cu−C phenyl distance was determined to be 1.947 Å. Al interaction with C phenyl in the native epoxy dimer has more ionic character rather than pure covalent as also observed in the Cu/epoxy study.…”

“…Between the two stable sites (N O h and O h ) identified for a given Al/D or Al/DwH model, an adsorption energy difference (ΔE ads ) is up to 0.28 eV. It implies a small energy anisotropy at the Al/epoxy interface when compared to the difference being 0.65 eV for the Cu/epoxy interface 20 considering the similar sites.…”

“…The pristine C 1s peak of the poly epoxy surface consists of three prominent components. 20,55 A main peak centered at a BE of 284.6 eV arises from aliphatic C or aromatic C contributions. A high BE shoulder (at 286.3 eV) presents C−O components and a π−π* shake up satellite at 291.2 eV.…”

“…19 Metallization of such epoxy polymers have found interest in high performance applications, to withstand drastic conditions. 20 Kanzow et al have described initial stage metal film growth in the case of noble metals such as Cu, Au, and Ag, which proceeds via Volmer−Weber (cluster) mode. 18 Also, at the initial stage of the metal layer formation, a phenomenological approach of progressive chemisorption of Al metal atoms on epoxy resin surfaces is proposed.…”

An anti-aging polymer electrolyte for flexible rechargeable zinc-ion batteries

“…As reported by Fourche, 38 chemical bonding takes place extensively in the case of polymer-metal interfaces; moreover, metal-polymer adsorption bonds (M-O-C) are observed for metals such as Al, Fe and Ni coated with epoxy. 39 Therefore, the covalent bonds (Zn-O-C) shown in Fig. 4e could form for ABSPEs under the Lewis acidbase reactions activated by the interfacial electrical eld.…”