The gas-phase structure of three copper amidinate compounds, copper(I)-N,N′-di-sec-butyl-acetamidinate (1), copper(I)-N-sec-butyl-2-iminopyrrolidinate (2), and copper(I)-N-tert-butyl-5,5-dimethyl-2-iminopyrrolidinate (3), and their initial adsorption on silicon oxide surfaces, were characterized by a combination of experimental measurements and density-functional theory (DFT) calculations. These compounds have previously been shown to crystallize in dimeric or tetrameric form, and liquid-injection field desorption ionization mass spectrometry data proved that such structures are retained upon vaporization into the gas phase (dimers for the first and third compounds, a tetramer for the second). Results from DFT calculations of the relative energies of formation of the monomers, dimers, and tetramers confirmed the experimental results. Adsorption on the surface of silicon oxide films was determined, based on additional DFT calculations, to lead to the binding of the copper amidinates preferentially as dimers; although the monomers form stronger bonds to the silicon surface because they bind directly through their copper atom, this cannot fully compensate for the large energy required to break the dimers apart. N 1s x-ray photoelectron spectroscopy data were used to corroborate both the presence of the dimers on the surface with the second (2) precursor and the threshold for their surface decomposition around room temperature. The behavior of the third compound is somewhat more complex, with some decomposition possibly happening immediately upon adsorption at 100 K.

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Surface-limited deposition reactions leading to the formation of copper nanoparticles on H-terminated Si(111) surface can serve as a model for understanding the role of structure of the deposition precursor molecules in determining the oxidation state of the metal deposited. This study compares three different precursor molecules: Cu(acac)2 (Cu(II) acetylacetonate), Cu(hfac)2, and Cu(hfac)VTMS (Cu(I)-(hexafluoroacetylacetonato)-vinyltrimethylsilane) as copper deposition sources in a process with a controlled oxidation state of copper. X-ray photoelectron spectroscopy suggests that single-electron reduction governs the deposition of Cu(I) from the first two precursor molecules and that the last of the precursors studied yields predominantly metallic copper. Time-of-fight secondary ion mass spectrometry (ToF-SIMS) and infrared spectroscopy are utilized to interrogate surface species produced. Atomic force microscopy is used to quantify the deposition process and to follow the size distribution of the deposited copper containing nanoparticles. A plausible explanation supported by density functional theory calculations is offered on the basis of the difference in the reaction pathways for Cu(I) and Cu(II) precursors.

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The poisoning of H2S sensing material based on the mixture of acid-treated carbon nanotubes, CuO and SnO2 was investigated by exposing the material to high doses of H2S (1% in volume) and following the changes spectroscopically. The presence of metal sulfides (CuS and SnS2), sulfates and thiols was confirmed on the surface of this material as the result of H2S poisoning. Further study revealed that leaving this material in air for extended period of time led to reoxidation of metal sulfides back to metal oxides. The formation of thiols and sulfates directly on carbon nanotubes is not reversible under these conditions; however, the extent of the overall surface reaction in this case is substantially lower than that for the composite material.