Performance limits of graphene-ribbon field-effect transistors

The performance of field effect transistors based on an single graphene ribbon with a constriction and a single back gate are studied with the help of atomistic models. It is shown how this scheme, unlike that of traditional carbon-nanotube-based transistors, reduces the importance of the specifics of the chemical bonding to the metallic electrodes in favor of the carbon-based part of device. The ultimate performance limits are here studied for various constriction and metal-ribbon contact models. In particular, we show that, even for poorly contacting metals, properly tailored constrictions can give promising values for both the on conductance and the subthreshold swing.

Representation of 2D objects with a topology preserving network

Comunicación presentada en el 2nd International Workshop on Pattern Recognition in Information Systems, Alicante, April, 2002.

Size-Dependent and Step-Modulated Supramolecular Electrochemical Properties of Catechol-Derived Adlayers at Pt(hkl) Surfaces

The electrochemical reactivity of catechol-derived adlayers is reported at platinum (Pt) single-crystal electrodes. Pt(111) and stepped vicinal surfaces are used as model surfaces possessing well-ordered nanometer-sized Pt(111) terraces ranging from 0.4 to 12 nm. The electrochemical experiments were designed to probe how the control of monatomic step-density and of atomic-level step structure can be used to modulate molecule–molecule interactions during self-assembly of aromatic-derived organic monolayers at metallic single-crystal electrode surfaces. A hard sphere model of surfaces and a simplified band formation model are used as a theoretical framework for interpretation of experimental results. The experimental results reveal (i) that supramolecular electrochemical effects may be confined, propagated, or modulated by the choice of atomic level crystallographic features (i.e.monatomic steps), deliberately introduced at metallic substrate surfaces, suggesting (ii) that substrate-defect engineering may be used to tune the macroscopic electronic properties of aromatic molecular adlayers and of smaller molecular aggregates.

Price promotions effects of virtue and vice products

Purpose: This paper aims to propose models that capture the own effect of price promotions of virtue and vice products on sales and cross effects within the subcategory, between subcategories and between periods. The hypotheses assume that, due to reverse consumption self-control, the demand for vice products is more price-sensitive than demand for virtue products, but the demand for vice products is less price-sensitive between periods than demand for virtue products; furthermore, due to the degree of impulse-buying and to licensing, the demand sensitivity of the products of a subcategory and of those of other subcategories varies according to the type of promoted product (vice or virtue). Design/methodology/approach: The methodology is based on different econometrical models that estimate the total net effect of price promotions of virtue and vice products on sales. Findings: The results show a greater own effect for price promotions of vice products than for virtue products. However, the complementary sales effect between subcategories for virtue products facilitates greater expansion of the subcategory in virtue products than in vice products. Originality/value: Although price promotions of virtue products (light) and vice products (regular) have proliferated in recent years, researchers have only estimated their own sales effect. Alternatively, the paper contributes by considering own and cross effects.