Alignment of liquid crystal/carbon nanotube dispersions for application in unconventional computing

We demonstrate the manipulation of single-walled carbon nanotube/liquid crystal composites using in-plane electric fields. The conductivity of the materials is shown to be dependant on the application of a DC bias across the electrodes. When the materials are subjected to this in-plane field, it is suggested that the liquid crystals orientate, thereby forcing the SWCNTs to follow in alignment. This process occurs over many seconds, since the SWCNTs are significantly larger in size than the liquid crystals. The opportunity for applying this material to unconventional computing problems is suggested

Evolution of Electronic Circuits using Carbon Nanotube Composites

Evolution-in-materio concerns the computer controlled manipulation of material systems using external stimuli to train or evolve the material to perform a useful function. In this paper we demonstrate the evolution of a disordered composite material, using voltages as the external stimuli, into a form where a simple computational problem can be solved. The material consists of single-walled carbon nanotubes suspended in liquid crystal; the nanotubes act as a conductive network, with the liquid crystal providing a host medium to allow the conductive network to reorganise when voltages are applied. We show that the application of electric fields under computer control results in a significant change in the material morphology, favouring the solution to a classification task

Modeling of axial heterostructure formation in ternary III-V nanowires

A model is proposed to depict the formation of axial heterostructure in ternary III-V nanowires (NW) grown by the catalytic vapor-liquid-solid (VLS) method. Our approach is based on the determination of chemical potential of a four-component liquid using the regular solution model and Stringfellow's scheme for the computation of the interaction coefficients of species present in the droplet. The model allows the estimation of the heterojunction width dependence on the growth temperature. This dependence has not been reported before by any previous theoretical studies. The AlGaAs/GaAs heterojunction formation in the Au-catalyzed AlGaAs NWs was considered as an example of ternary system. The heterojunction width was found to increase with the growth temperature with a second-order polynomial dependence

Metallization and stiffness of the Li-intercalated MoS2 bilayer

Performed density-functional theory (DFT) calculations have shown that the Li adsorption on the MoS2 (0 0 0 1) surface, as well as Li intercalation into the space between MoS2 layers, transforms the semiconductor band structure of MoS2 into metallic. For the (√3 × √3) – R30° Li layer, the band structures of the MoS2 bilayer with adsorbed and intercalated Li are very similar, while for higher Li concentrations, the character of metallization for the adsorbed layer substantially differs from that of the MoS2–Li–MoS2 layered system. In particular, for the adsorbed (1 × 1) Li monolayer, the increased density of the layer leads to the nonmetal-to-metal transition, which is evident from the appearance of the band crossing EF with an upward dispersion, pertinent to simple metals. It has been demonstrated that intercalated Li substantially increases the interlayer interaction in MoS2. Specifically, the estimated 0.12 eV energy of the interlayer interaction in the MoS2 bilayer increases to 0.60 eV. This result is also consistent with results of earlier DFT calculations and available experimental results for alkali-intercalated graphene layers, which have demonstrated a substantial increase in the stiffness due to intercalation of alkalis

Lithography-free high aspect ratio submicron quartz columns by reactive ion etching

We describe lithography-free fabrication of sub-micron surface features on quartz substrates by the reactive ion etching (RIE) in a CF4/Ar atmosphere. These submicron glass columns are well defined, have a high aspect ratio, with the underlying substrate being very flat. The geometry of the fabricated surface columns is dependent on the RIE process parameters. The analysis of these glass columns shows that a differential etching process takes place. The optical characterization of these samples shows a significant absorption at visible wavelengths whereas the relative transmission is very high in the infrared range, suggesting that these samples could potentially be used for wavelength selection device applications

Modeling the nucleation statistics in vapor-liquid-solid nanowires

The statistics of nucleation events in nanowires growing via the vapor–liquid–solid mechanism in the mononuclear regime is studied theoretically. A semi-analytical model is developed which is capable of describing the distributions of time intervals between the successive nucleation events and some other useful characteristics of nucleation statistics. Our model accounts for desorption from the droplet, which was not included in the previous studies of nucleation statistics. It is shown that the relative dispersion of nucleation distributions increases with the nanowire radius and at a higher desorption rate from the droplet, leading to the corresponding broadening of the length distribution. Using the model is also shown to fit well experimental data available on nucleation statistics in the Au-catalyzed Si and III–V nanowires