The interaction of water vapor on clean diamond (100) has been studied using ultraviolet photoemission spectroscopy (UPS), X-ray photoemission spectroscopy (XPS), X-ray-absorption near-edge structure (XANES) spectroscopy, and high-resolution electron energy loss spectroscopy (HREELS). It is shown that water dissociates at room temperature on clean diamond forming C-H and C-OH bonds, resulting in a surface dipole layer which produces the condition of negative electron affinity (NEA). The strong polarization dependence of the O K XANES could be associated with the out-of-plane orientation of the OH bonds. Density functional theory (DFT) calculations confirm the existence of NEA on this surface with a mixture of hydrogen and hydroxyl (OH) terminations.

The adsorption of allyl alcohol, acrylic acid, and allyl chloride, as well as unsaturated organic molecules such as acetylene and 1,3 butadiene, on reconstructed diamond (100) 2 x 1 have been investigated using high-resolution electron energy loss (HREELS) spectroscopy and synchrotron radiation spectroscopy. The cycloadditions of these organic molecules produce chemically adsorbed adlayers with varying degree of coverages on the clean diamond. The organic adsorbed surface has a lowered electron affinity and shows a secondary electron yield that varies between 12 and 40% of the yield obtained from a fully hydrogenated diamond surface. The diamond surface can be functionalized with hydroxyl, carboxylic, and chlorine functionalities by the adsorption of these allyl organics. The [2 + 2] adduct of acetylene on the diamond (100) 2 x 1 surface can be observed. 1,3-butadiene attains a higher coverage as well as forms a thermally more stable adlayer on the diamond surface compared to the other organic molecules, due to its ability to undergo [4 + 2] cycloaddition.

The tuning of electron affinity and secondary electron emission on diamond (100) surfaces due to cycloaddition with 1,3-butadiene is investigated by photoemission experiments and density functional theory (DFT) calculations. A significant reduction in electron affinity up to 0.7 eV and enhancement of secondary electron emission were observed after 1,3-butadiene adsorption. The lowering of vacuum level via 1,3-butadiene adsorption is supported by DFT calculations. The C-H bonds in the covalently bonded organics on diamond contribute to the enhanced secondary electron emission and reduced electron affinity in a mechanism similar to that of C-H bonds on hydrogenated diamond surfaces. This combination of strong secondary emission and low electron affinity by the organic functionalization of diamond has potential applications in diamond-based molecular electronic devices.

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We report for the first time the direct deposition of crystalline molybdenum sulfide (MoS2) using a single-source precursor based on tetrakis(diethylaminodithiocarbomato)molybdate(IV) (abbreviated as Mo(Et2NCS2)4). The chemistry of this precursor adsorbed on a range of substrates (silicon, germanium, gold-coated germanium, nickel, etc.) has been studied using in situ X-ray photoelectron spectroscopy. The Mo(Et2NCS2)4 precursor can be evaporated at 300 °C; its vapor adsorbs on most surfaces at room temperature and decomposes by 400 °C to form crystalline MoS2. Using this method, high-quality, basal plane-oriented MoS2 can be grown on nickel by a one-step thermal evaporation process for the first time. Interestingly, choosing elemental substrates which form eutectic alloys with gold favors the elimination of sulfur from the MoS2 film. This results in Mo intermetallic compound formation at the eutectic temperatures of the Au and substrate element. Unpredecented low-temperature growth of tetragonal MoSi2 or orthorhombic MoGe2 on Au-coated silicon or germanium, respectively, has been obtained via this eutectic phase-mediated diffusional reaction. Hollow carbon nanofibers are produced if the precursor is dosed onto Au−Si substrate at 1000 °C, mediated by the catalytic effect of Au−Mo.

We investigate the interface between a C(60) fullerite film, C(60)F(36), and diamond (100) by using core-level photoemission spectroscopy, cyclic voltammetry (CV), and high-resolution electron energy loss spectroscopy (HREELS). We show that C(60) can be covalently bonded to reconstructed C(100)-2x1 and that the bonded interface is sufficiently robust to exhibit characteristic C(60) redox peaks in solution. The bare diamond surface can be passivated against oxidation and hydrogenation by covalently bound C(60). However, C(60)F(36) is not as stable as C(60) and desorbs below 300 degrees C (the latter species being stable up to 500 degrees C on the diamond surface). Neither C(60) fullerite nor C(60)F(36) form reactive interfaces on the hydrogenated surface-they both desorb below 300 degrees C. The surface transfer doping process of hydrogenated diamond by C(60)F(36) is the most evident one among all the adsorbate systems studied (with a coverage-dependent band bending induced by C(60)F(36)).

A novel sorbent for SO2 removal has been investigated. The sorbent is obtained by conventional incipient wetness impregnation of abandoned biomaterials (straw or dried leaves) with an aqueous solution of Na2CO3. A material with the composition 80 wt % Na2CO3/straw shows a desulfurization activity which is both higher and faster than that of the reference sample Na2CO3/gamma-Al2O3. The breakthrough and stoichiometric SO2 adsorption efficiencies for 80 wt % Na2CO3/straw reach 48.9% and 80.6%, respectively, at a temperature of 80 degrees C. The adsorption efficiencies are almost constant in the temperature range 70 to 300 degrees C. According to IR and XPS analysis the main products observed on the spent sorbent are sulfite below 150 degrees C and sulfate at 300 degrees C. The Na2CO3 in 80 wt % Na2CO3/straw can potentially be recycled by the oxidation of the straw with concomitant reduction of the sulfite species to elemental sulfur, making the proposed process CO2 neutral.

Ultrathin layers of organic molecules can be assembled on group IV (e.g., silicon, germanium, diamond) semiconductor surfaces using surface analogues of cycloaddition reactions. We present a study of the chemisorption of benzene, toluene, and styrene on the Pandey chain of C(111) using high resolution electron energy loss spectroscopy and density functional theory calculations. Two cycloaddition reactions, namely, the [4 + 2] and [2 + 2], were examined. The [4 + 2] reaction is found to be thermodynamically unfavorable on C(111), while the [2 + 2] reaction involving the ring is slightly exothermic. In the case of aromatic molecules with an external unsaturated functional group, the reaction can proceed via the external functionality, thereby preserving the aromatic ring and providing further stability. Different reactivity patterns to the C(100) surface are rationalized on the basis of steric effects imposed by the geometrical structure of the Pandey chain. Our study demonstrates the potential of employing the Pandey chain as a template for assembling one-dimensional molecular structures on the diamond surface.