With its exceptional charge mobility, graphene holds great promise for applications in next-generation electronics. In an effort to tailor its properties and interfacial characteristics, the chemical functionalization of graphene is being actively pursued. The oxidation of graphene via the Hummers method is most widely used in current studies, although the chemical inhomogeneity and irreversibility of the resulting graphene oxide compromises its use in high-performance devices. Here, we present an alternative approach for oxidizing epitaxial graphene using atomic oxygen in ultrahigh vacuum. Atomic-resolution characterization with scanning tunnelling microscopy is quantitatively compared to density functional theory, showing that ultrahigh-vacuum oxidization results in uniform epoxy functionalization. Furthermore, this oxidation is shown to be fully reversible at temperatures as low as 260 °C using scanning tunnelling microscopy and spectroscopic techniques. In this manner, ultrahigh-vacuum oxidation overcomes the limitations of Hummers-method graphene oxide, thus creating new opportunities for the study and application of chemically functionalized graphene.

The adsorbed states of ethylene on the Si(100)c(4×2), Si(100)(2×1), and the Si(100) 9° vicinal surfaces have been studied using high resolution electron energy loss spectroscopy (EELS) and low-energy electron diffraction (LEED). Ethylene is nondissociatively chemisorbed on the Si(100) surface in the wide temperature range between 77 and ∼600 K, and is rehybridized to have a near sp3 hybridization state. The adsorbed structure is proposed in which ethylene is di-σ bonded to two adjacent Si atoms of the dimer at the Si(100) surface. The thermal decomposition of chemisorbed ethylene and the influence of steps on the adsorbed states of ethylene are discussed.

The occupied and unoccupied in-gap electronic states of a Rh-doped SrTiO3 photocatalyst were investigated by X-ray emission spectroscopy and X-ray absorption spectroscopy for different Rh impurity valence states and doping levels. An unoccupied midgap Rh4+ acceptor state was found 1.5 eV below the SrTiO3 conduction band minimum. Both Rh4+ and Rh3+ dopants were found to have an occupied donor level close to the valence band maximum of SrTiO3. The density of states obtained from first-principles calculations show that all observed spectral features can be assigned to electronic states of substitutional Rh at the Ti site and that Rh:SrTiO3 is an unusual titanate compound with a characteristic p-type electronic structure. The Rh doping results in a large decrease of the bandgap energy, making Rh:SrTiO3 an attractive material for use as a visible-light-driven H2-evolving photocatalyst in a solar water splitting reaction.

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Thermal excitation of adsorbed oxygen species is found to initiate the CO oxidation on Pt͑111͒. We have prepared three different coadsorption systems to study the reactivity of different oxygen species; ͑1͒ CO on the O 2 preadsorbed Pt͑111͒ surface, ͑2͒ CO on the nearly perfect Pt͑111͒ p(2ϫ2)-O surface, and ͑3͒ CO on the disordered atomic oxygen-preadsorbed Pt͑111͒ surface. Four CO 2 desorption peaks ͑␣-CO 2 at 125 K, ␤ 3 -CO 2 at ϳ225 K, ␤ 2 -CO 2 at ϳ260 K, and ␤ 1 -CO 2 at 320 K͒ are observed. The desorption temperatures of CO 2 strongly depend on the adsorbed states of oxygen species. We have shown that the ␣-CO 2 state, ␤ 2,3 -CO 2 states, and ␤ 1 -CO 2 state are correlated with adsorbed O 2 , disordered oxygen atoms, and p͑2ϫ2͒ oxygen atoms, respectively. The difference in CO 2 desorption temperature is related to thermal excitation of each oxygen species, which is derived from the structural information of coadsorbed states during thermal evolution by means of low-energy electron diffraction and infrared reflection absorption spectroscopy.