Size effects in surface reconstructed <100><100> and <110>< 110> silicon nanowires

The geometrical and electronic structure properties of $$and$$ silicon nanowires in the absence of surface passivation are studied by means of density-functional calculations. As we have shown in a recent publication [R. Rurali and N. Lorente, Phys. Rev. Lett. {\bf 94}, 026805 (2005)] the reconstruction of facets can give rise to surface metallic states. In this work, we analyze the dependence of geometric and electronic structure features on the size of the wire and on the growth direction

Band gap engineering of MoS2_2 upon compression

Molybdenum disulfide (MoS$_2$) is a promising candidate for 2D nanoelectronic devices, that shows a direct band-gap for monolayer structure. In this work we study the electronic structure of MoS$_2$ upon both compressive and tensile strains with first-principles density-functional calculations for different number of layers. The results show that the band-gap can be engineered for experimentally attainable strains (i.e. $\pm 0.15$). However compressive strain can result in bucking that can prevent the use of large compressive strain. We then studied the stability of the compression, calculating the critical strain that results in the on-set of buckling for free-standing nanoribbons of different lengths. The results demonstrate that short structures, or few-layer MoS$_2$, show semi-conductor to metal transition upon compressive strain without bucking

On the properties of surface reconstructed silicon nanowires

We study by means of density-functional calculations the role of lateral surface reconstructions in determining the electrical properties of silicon nanowires. The different lateral reconstructions are explored by relaxing all the nanowires with crystalline bulk silicon structure and all possible ideal facets that correspond to an average diameter of 1.5 nm. We show that the reconstruction induces the formation of ubiquitous surface states that turn the wires into semi-metallic or metallic

Nanofils de silici : com més llargs, millors

Investigadors de la UAB han estudiat un dels més prometedors sistemes unidimensionals per a futures aplicacions en el camp de la nanoelectrònica: els nanofils de silici. Els científics han aconseguit estudiar sistemes més llargs que els analitzats fins ara i han conclòs que són més realistes i tenen una física molt més rica.Investigadores de la UAB han estudiado uno de los más prometedores sistemas unidimensionales para futuras aplicaciones en el campo de la nanoelectrónica: los nanohilos de silicio. Los científicos han conseguido estudiar sistemas más largos que los analizados hasta ahora y han llegado a la conclusión de que son más realistas y tienen una física mucho más rica.UAB researchers have studied one of the most promising unidimensional systems for future applications in the nanoelectronics field: the silicon nanowires. The scientists have studied silicon nanowires longer than those analyzed until now, and have concluded that are more realistic systems and with a much richer physics

Metallic and semi-metallic <100> silicon nanowires

Silicon nanowires grown along the -direction with a bulk Si core are studied with density functional calculations. Two surface reconstructions prevail after exploration of a large fraction of the phase space of nanowire reconstructions. Despite their energetical equivalence, one of the reconstructions is found to be strongly metallic while the other one is semi-metallic. This electronic-structure behavior is dictated by the particular surface states of each reconstruction. These results imply that doping is not required in order to obtain good conducting Si nanowires.Comment: 13 pages, 4 figures; Phys. Rev. Lett., in pres

Spin transport in dangling-bond wires on doped H-passivated Si(100)

New advances in single-atom manipulation are leading to the creation of atomic structures on H passivated Si surfaces with functionalities important for the development of atomic and molecular based technologies. We perform total-energy and electron-transport calculations to reveal the properties and understand the features of atomic wires crafted by H removal from the surface. The presence of dopants radically change the wire properties. Our calculations show that dopants have a tendency to approach the dangling-bond wires, and in these conditions, transport is enhanced and spin selective. These results have important implications in the development of atomic-scale spintronics showing that boron, and to a lesser extent phosphorous, convert the wires in high-quality spin filters.Comment: 11 pages, 4 figure