Rotated domains in chemical vapor deposition-grown monolayer graphene on Cu(111): an angle-resolved photoemission study.

Copper is considered to be the most promising substrate for the growth of high-quality and large area graphene by chemical vapor deposition (CVD), in particular, on the (111) facet. Because the interactions between graphene and Cu substrates influence the orientation, quality, and properties of the synthesized graphene, we studied the interactions using angle-resolved photoemission spectroscopy. The evolution of both the Shockley surface state of the Cu(111) and the π band of the graphene was measured from the initial stage of CVD growth to the formation of a monolayer. Graphene growth was initiated along the Cu(111) lattice, where the Dirac band crossed the Fermi energy (EF) at the K point without hybridization with the d-band of Cu. Then two rotated domains were additionally grown as the area covered with graphene became wider. The Dirac energy was about -0.4 eV and the energy of the Shockley surface state of Cu(111) shifted toward the EF by ~0.15 eV upon graphene formation. These results indicate weak interactions between graphene and Cu, and that the electron transfer is limited to that between the Shockley surface state of Cu(111) and the π band of graphene. This weak interaction and slight lattice mismatch between graphene and Cu resulted in the growth of rotated graphene domains (9.6° and 8.4°), which showed no significant differences in the Dirac band with respect to different orientations. These rotated graphene domains resulted in grain boundaries which would hinder a large-sized single monolayer growth on Cu substrates.

Patterning of self-assembled pentacene nanolayers by extreme ultraviolet-induced three-dimensional polymerization.

Most researchers expect extreme ultraviolet lithography (EUVL) to be used to create patterns below 32 nm in semiconductor devices. An ultrathin EUV photoresist (PR) layer a few nanometers thick is required to further reduce the minimum feature size. Here, we show for the first time that pentacene molecular layers can be employed as a new EUV resist. Nanometer-scale dots and lines have been successfully realized using the new molecular resist. We clearly show the mechanism that forms the nanopatterns using a scanning photoemission microscope, EUV interference lithography, an atomic force microscope, and photoemission spectroscopy. The molecular PR has several advantages over traditional polymer EUV PRs. For example, it has high thermal/chemical stability, negligible outgassing, the ability to control the height and width on the nanometer scale, fewer residuals, no need for a chemical development process and thus a reduction of chemical waste when making nanopatterns. Besides, it can be applied to any substrate to which pentacene bonds chemically, such as SiO2, SiN, and SiON, which are important films in the semiconductor device industry.

A compact, sample-in-atmospheric-pressure soft x-ray microscope developed at Pohang Light Source.

A full-field transmission soft x-ray microscope (TXM) was developed at the Pohang Light Source. With a 2 mm diameter condenser zone plate and a 40 nm outermost-zone-width objective zone plate, the TXM's achieved spatial resolution is better than 50 nm at the photon energy of 500 eV (wavelength: 2.49 nm). The TXM is portable and mounted in tandem with a 7B1 spectroscopy end station. The sample position is outside the vacuum, allowing for quick sample changes and enhanced in situ experimental capability. In addition, the TXM is pinhole-free and easy to align, having commercial mounts located outside the vacuum components.

Metal-insulator transition-induced adsorption-resistant behavior of small Au nanoparticles.

Smaller nonmetallic nanoparticles are more inert: Metal-insulator transition of Au nanoparticles on silica is closely related to the metal-support charge transfer, which has a strong influence on chemisorption reactivity of Au. Smaller nonmetallic Au nanoparticles are more resistant towards butanethiol chemisorption [picture and graph: see text].The size-dependent variation of the electronic and chemical properties of Au nanoparticles formed on native Si oxide surfaces is investigated using synchrotron radiation photoemission spectroscopy and ultraviolet photoelectron spectroscopy. The adsorption reactivity toward butanethiol adsorption initially increases with decreasing particle size; however, the reactivity of Au nanoparticles becomes gradually lower below a size of approximately 0.8 nm. The photoemission spectral changes suggest a metal-insulator transition, accompanied by negative charge transfer from the nanoparticles to the support, which may be the source of the chemical inertness of small Au nanoparticles.