Four-fold Raman enhancement of 2D band in twisted bilayer graphene: evidence for a doubly degenerate Dirac band and quantum interference.

We report the observation of a strong 2D band Raman in twisted bilayer graphene (tBLG) with large rotation angles under 638 nm and 532 nm visible laser excitations. The 2D band Raman intensity increased four-fold as opposed to the two-fold increase observed in single-layer graphene. The same tBLG samples also exhibited rotation-dependent G-line resonances and folded phonons under 364 nm UV laser excitation.

Sum frequency generation spectroscopy study of an ionic liquid at a graphene-BaF2 (111) interface.

Sum frequency generation (SFG) vibrational spectroscopy and contact angle measurements of an ionic liquid, 1-butyl-3-methylimidazolium dicyanamide [BMIM][DCA], at solid-liquid interfaces are reported. Bare solid single crystal BaF2 (111) surface, a single and few layer graphene-coated BaF2 (111) surface are used as the solid substrates. The SFG results indicate that both [BMIM](+) and [DCA](-) can be detected specifically on the graphene-coated BaF2 (111) surface, without coating only [DCA](-) are observed.

Control of thickness uniformity and grain size in graphene films for transparent conductive electrodes.

Large-scale and transferable graphene films grown on metal substrates by chemical vapor deposition (CVD) still hold great promise for future nanotechnology. To realize the promise, one of the key issues is to further improve the quality of graphene, e.g.

Control and characterization of individual grains and grain boundaries in graphene grown by chemical vapour deposition.

The strong interest in graphene has motivated the scalable production of high-quality graphene and graphene devices. As the large-scale graphene films synthesized so far are typically polycrystalline, it is important to characterize and control grain boundaries, generally believed to degrade graphene quality. Here we study single-crystal graphene grains synthesized by ambient chemical vapour deposition on polycrystalline Cu, and show how individual boundaries between coalescing grains affect graphene's electronic properties.

Mechanism of horizontally aligned growth of single-wall carbon nanotubes on R-plane sapphire.

As a promising one-dimensional material for building nanodevices, single-wall carbon nanotubes (SWNTs) should be organized into a rational architecture on the substrate surface. In this study, horizontally aligned SWNTs with two alignment modes were synthesized on the same R-plane sapphire wafer by chemical vapor deposition with cationized ferritins as catalysts. In the middle part of the wafer, SWNTs were aligned on the R-plane sapphire in the direction [1101].