A wide band gap metal-semiconductor-metal nanostructure made entirely from graphene

A blueprint for producing scalable digital graphene electronics has remained elusive. Current methods to produce semiconducting-metallic graphene networks all suffer from either stringent lithographic demands that prevent reproducibility, process-induced disorder in the graphene, or scalability issues. Using angle resolved photoemission, we have discovered a unique one dimensional metallic-semiconducting-metallic junction made entirely from graphene, and produced without chemical functionalization or finite size patterning. The junction is produced by taking advantage of the inherent, atomically ordered, substrate-graphene interaction when it is grown on SiC, in this case when graphene is forced to grow over patterned SiC steps. This scalable bottomup approach allows us to produce a semiconducting graphene strip whose width is precisely defined within a few graphene lattice constants, a level of precision entirely outside modern lithographic limits. The architecture demonstrated in this work is so robust that variations in the average electronic band structure of thousands of these patterned ribbons have little variation over length scales tens of microns long. The semiconducting graphene has a topologically defined few nanometer wide region with an energy gap greater than 0.5 eV in an otherwise continuous metallic graphene sheet. This work demonstrates how the graphene-substrate interaction can be used as a powerful tool to scalably modify graphene's electronic structure and opens a new direction in graphene electronics research.Comment: 11 pages, 7 figure

Silicon intercalation into the graphene-SiC interface

In this work we use LEEM, XPEEM and XPS to study how the excess Si at the graphene-vacuum interface reorders itself at high temperatures. We show that silicon deposited at room temperature onto multilayer graphene films grown on the SiC(000[`1]) rapidly diffuses to the graphene-SiC interface when heated to temperatures above 1020. In a sequence of depositions, we have been able to intercalate ~ 6 ML of Si into the graphene-SiC interface.Comment: 6 pages, 8 figures, submitted to PR

Autoimmune diabetes is regulated by the vanilloid receptor 1 ligand capsaicin

Vanilloid receptor 1 (VR1) is expressed on immune cells as well as on sensory neurons. Here we report that VR1 can regulate immunological events in the gut in response to its ligand capsaicin (CP), a nutritional factor and the pungent component of chili peppers. Orally administered CP attenuates the proliferation and activation of auto-reactive T cells in pancreatic lymph nodes (PLN) and protects mice from development of type 1 diabetes (T1D). Engagement of VR1 enhances a discreet population of CD11b+/F4/80 + macrophages that express anti-inflammatory factors such as IL-10 and PD-L1. This macrophage population is essential for CP mediated attenuation of T cell proliferation. VR1 expression is required for CP to inhibit proliferation of auto-reactive T cells. The protective effect is partially restored in (VR1 +/+→VR1−/− bone marrow (BM) chimeric mice, implying that the role of VR1 may involve crosstalk between neuronal and immunological systems in vivo. Furthermore, engagement of VR1 enhances a population of Tr1-like cells in the PLN which may be able to protect naïve NOD from onset of T1D upon adoptive transfer. These findings suggest that exogenous and perhaps endogenous ligands of VR1 can have profound effects on the development of gut mediated immune tolerance and autoimmunity by directly influencing the immune system.