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The adsorption of aromatic thiols on Cu and the SAM film stability in acidic solutions have been studied by XPS, contact angle and electrochemical techniques. Three short molecules, benzenethiol (BT), 2-naphthalenethiol (2-NT) and 4-acetamidothiophenol (4-AA), were selected as representatives of aromatic thiols to highlight the effect of aromatic rings and hydrophilic terminal groups on the copper protection. All the three molecules form stable S-Cu bonds as a consequence of their adsorption process on polycrystalline copper. Although none of them provides a full copper passivation, the adsorbed films persist without major degradation on Cu electrodes even after 12 h immersion in 0.5 M sulfuric acid. Comparing the freshly prepared adsorbed films, the larger 2-NT molecule provides a better Cu passivation, but the shorter BT molecule favours a higher surface coverage. The terminal groups of 4-AA are responsible for a higher Cu surface wettability in water, compared to that with SAMs of the other molecules, and allow for an easier charge-transfer to the electrolyte and for a higher electrochemical capacitance. After long enough ageing, however, the 4-AA-based molecular films are able to self-organize and to provide a steadily improving copper passivation. Adlayers of the BT and 2-NT molecules, on the contrary, over a long time tend to protect less and less the Cu substrate, probably because of progressive electrolyte infiltration.

Electrodeposition from ZnCl2 aqueous solution was performed to grow ZnO thin films on the surface of polycrystalline copper plates. Electrochemical parameters for deposition were optimized by means of cyclic voltammetry (CV). The morphology of the deposits was studied via scanning electron microscopy (SEM), and their chemical composition was ascertained by means of X-ray photoelectron spectroscopy (XPS). The effects of changing the deposition bath temperature (T (bath)) and the role played by post-deposition treatments, such as temperature and time of annealing in air, were studied. SEM images of freshly deposited vs. annealed samples have shown that in the former case the films display a rough morphology with mixed grain/hexagonal platelets structures and in the latter smaller but more uniformly dispersed cubic grains. T (bath) is found to be the key parameter to induce the different morphology in the deposited films, which reflects in a different chemical reactivity of surface species, as found on the basis of the binding energies and relative quantitative ratios between Zn 2p and O 1s peaks. In fact, a higher T (bath) favours a more efficient desorption of OH groups upon annealing, the O 1s peak resulting to much more drastically modified oxide/hydroxide intensity ratio with respect to the case of the sample deposited at lower T (bath)

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Copper corrosion in alkaline solutions is inhibited by the formation of self-assembled monolayers of aromatic thiols, made of either benzenethiol or 2-naphthalenethiol or 4-acetamidothiophenol. Electrochemical experiments, based on voltammetry and impedance spectroscopy, point out the much lower reactivity of copper surfaces towards oxidation, when covered by compact adlayers of the above molecules bonded through the S atom. The peculiar shape and peak position in the voltammetric reduction of residual oxides grown on modified metal surfaces suggest that they are due to Cu(I) suboxides, probably grown on reactive metal defects. XPS experiments have confirmed that the aromatic adlayers are still covering most of the Cu surface even after 1 h immersion in 0.5 M NaOH. The main changes in Auger and XP spectra indicate the formation of much less Cu(2)O in the protected samples than in the corresponding bare Cu aged in NaOH. From the experimental data the presence of defective copper oxides on modified Cu has been deduced.