A non-dispersive Raman D-band activated by well-ordered interlayer interactions in rotationally stacked bi-layer Graphene

Raman measurements on monolayer graphene folded back upon itself as an ordered but skew-stacked bilayer (i.e. with interlayer rotation) presents new mechanism for Raman scattering in sp2 carbons that arises in systems that lack coherent AB interlayer stacking. Although the parent monolayer does not exhibit a D-band, the interior of the skewed bilayer produces a strong two-peak Raman feature near 1350 cm-1; one of these peaks is non-dispersive, unlike all previously observed D-band features in sp2 carbons. Within a double-resonant model of Raman scattering, these unusual features are consistent with a skewed bilayer coupling, wherein one layer imposes a weak but well-ordered perturbation on the other. The discrete Fourier structure of the rotated interlayer interaction potential explains the unusual non-dispersive peak near 1350 cm-1

Clathrate Structure for Electronic and Electro-Optic Applications

A method including the steps of (a) depositing a metal layer on a selected portion of a silicon substrate under a first set of predetermined conditions to form an metal silicide layer and an intermediate n-type silicon layer; and (b) exposing the metal silicide layer and the n-type silicon layer to a second set of predetermined conditions to form a silicon clathrate film on the selected portion of the silicon substrate, where the intermediate n-type silicon layer acts to bond the silicon clathrate to the silicon substrate to form a silicon clathrate structure

Top-Down Structure and Device Fabrication using \u3ci\u3eIn Situ\u3c/i\u3e Nanomachining

We demonstrate the potential of an alternative tool for the fabrication of nanoscale structures and devices. A nanoindenter integrated with an atomic force microscope is shown to be a powerful machine tool for cutting precise length nanowires or nanobelts and for manipulating the shortened wires. We also demonstrate its utility in cutting grooves and fabricating dents (or periodic arrays of dents) in ZnSnanobelts. This approach permits the direct mechanical machining of nanodevices that are supported on a substrate without the inherent complications of e beam or photolithography

Laser ablation for the synthesis of carbon nanotubes

Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces and output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred

Laser ablation for the synthesis of carbon nanotubes

Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces an output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of side pumped, preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred

Thermolectric Materials Based on Intercalated Layered Metallic Systems

A novel thermoelectric material in the form of a unit cell including a first reagent intercalated as a semiconducting layer into a metallic layered host and a method for producing the thermoelectric material are disclosed. The unit cell is characterized by a Seebeck coefficient S of 80-140 μV/K° and an electrical conductivity σ of 103 -104 (Ωcm)-1, as well as a figure of merit Z of about 2×10-3 K-1 at 100° K

Silicon Nanowires: Doping Dependent N- And P- Channel FET Behavior

The electrical transport properties of field effect transistor (FET) devices made of silicon nanowires (SiNWs) synthesized by pulsed laser vaporization (PLV) were studied. From as-grown PLV-SiNW FET, we found p-channel FET behavior with low conductance. To improve conductance, spin on glass (SOG) and vapor doping were used to dope phosphorus and indium into SiNW, respectively. From doping after synthesis, we could successfully make both n- and p-channel FET devices

Metallic Nanoscale Fibers from Stable Iodine-Doped Carbon Nanotubes

A method of doping involves soaking single-walled carbon nanotubes in molten iodine. Excess physisorbed iodine may then be removed by annealing

\u3ci\u3eIn-Situ\u3c/i\u3e Raman Scattering Studies of Alkali-Doped Single Wall Carbon Nanotubes

Electrochemical doping and in-situ Raman scattering were used to study charge transfer in K- and Li-doped single wall carbon nanotubes (SWNT) as a function of alkali concentration. An 8 cm-1 downshift was observed for the tangential phonon mode of SWNT doped to stoichiometries of KC24 and Li1.25C6. The shift in both systems is reversible upon de-doping despite an irreversible loss of crystallinity. These results indicate that the tangential mode shifts result from electron transfer from alkali dopants to the SWNT, and that these modes are only weakly affected by long-range order within the ropes