We have investigated the transport properties of topological insulator based on single-crystal Bi0.83Sb0.17 nanowires. The single-crystal nanowire samples in the diameter range 200 nm – 1.1 μm were prepared by the high frequency liquid phase casting in a glass capillary using an improved Ulitovsky technique; they were cylindrical single-crystals with (1011) orientation along the wire axis. In this orientation, the wire axis makes an angle of 19.5o with the bisector axis C1 in the bisector-trigonal plane. Bi0.83Sb0.17 is a narrow gap semiconductor with energy gap at L point of Brillouin zone ΔE= 21 meV. In accordance with the measurements of the temperature dependence of the resistivity of the samples resistance increases with decreasing temperature, but at low temperatures decrease in the resistance is observed. This effect, decrease in the resistance, is a clear manifestation of the interesting properties of topological insulators - the presence on its surface of a highly conducting zone. The Arrhenius plot of resistance R in samples with diameter d=1.1 µm and d=200 nm indicates a thermal activation behavior with an activation gap ΔE= 21 and 35 meV, respectively, which proves the presence of the quantum size effect in these samples. We found that in the range of diameter 1100 nm - 200 nm when the diameter decreases the energy gap is growing as 1/d. We have investigated magnetoresistance of Bi0.83Sb0.17 nanowires at various magnetic field orientations. From the temperature dependences of Shubnikov de Haas oscillation amplitude for different orientation of magnetic field we have calculated the cyclotron mass mc and Dingle temperature TD for longitudinal and transverse (B||C3 and B||C2) directions of magnetic fields, which equal 1.96*10-2m0, 9.8 K, 8.5*10-3m0 , 9.4 K and 1.5*10-1m0 , 2.8 K respectively. The observed effects are discussed.

Silicon (Si) nanowires offer great potential for field ionization (FI) applications due to well-established Si microfabrication methods combined with favorable ionizing properties of Si. Band bending of semiconductors under applied electric fields increases the FI probability, which is not possible with metal-based counterparts. While it has been demonstrated that scaling down the active material geometry can increase the FI efficiency, maximum electric field at the tip of a single nanowire decreases by quenching effect of nearby nanowires. In this work, optimization of Si nanowire geometries for improved FI efficiencies is explored.

Formation of patterned metal and semiconductor (e.g. silicon) nanowires is achieved using anodic aluminum oxide (AAO) templates with porous structures of different heights resulting from an initial step difference made by etching the aluminum (Al) thin film with a photoresist developer prior to the anodization process. This approach allows for the growth of vertically aligned nanowire arrays on a metal substrate, instead of an oriented semiconductor substrate, using an electroplating or a chemical vapor deposition (CVD) process. The vertically aligned metal and semiconductor nanowires defined on a metal substrate could be applied to the realization of vertical 3D transistors, field emission devices, or nano-micro sensors for biological applications.

The high carrier concentrations typically reported for nanowire devices indicate that when Schottky barrier transport is present, it occurs in the thermionic field emission regime with a substantial but not exclusive tunneling component. Analysis by thermionic field emission is difficult due to its multivariate nature. In recent work, we developed a mathematical stability approach that greatly simplified the evaluation of the multivariate thermionic field emission parameters. This is a general method with potentially wide applicability, requiring only the effective mass m* and relative dielectric constant εr for a given semiconductor as inputs. In the present work, we investigate the influence of the materials properties effective mass m* and relative dielectric constant εr on stability for a range of real and simulated semiconductor nanowires. A further investigation of temperature sensitivity and regime trends is presented.

We present a concept to increase efficiencies utilizing nonlinear elements integrated with our semiconductor nanowire networks. Demonstrated here is power generation with thermoelectric devices made of two nanowire networks, one silicon and one indium phosphide, grown on a mechanically flexible copper substrate. Electron microscopy was utilized to characterize structural integrity of the nanowire networks. Non-linear current-voltage characteristics were observed, which suggests a new platform to increase maximum electrical power generation for a given temperature gradient.

Zinc oxide (ZnO) is a crystalline material with diverse morphology, large bandgap and high visible light transparency. All of these characteristics make ZnO a suitable material for applications in optical devices such as photovoltaic cells and photodiodes. Regarding photovoltaic applications, it is necessary to grow ZnO on a transparent conducting oxide (TCO) substrate. In this work, vertically aligned 1-dimensional ZnO have been synthesized on a TCO substrate through chemical vapor deposition (CVD). Although ZnO is capable of being synthesized at lower temperatures through the use of Zn powder precursor, oxidation of precursor remains a significant limiting factor to control dimensional characteristics of the synthesized product.

In our work we have developed a method by which ZnO is synthesized under lower temperatures through the prevention of precursor oxidation and control of Zn vapor fluid dynamics. Partial pressure of Zn vapor—a significant factor in the morphology and quality of product—is controlled and maintained during growth. The morphology and crystal structure of the synthesized ZnO is characterized by scanning electron microscopy (SEM) and x-ray diffraction (XRD). We also demonstrate the fabrication of dye-sensitized solar cell (DSSC) with synthesized 1-dimensional ZnO, as a photoelectrode, and compare the photovoltaic characteristics of two devices fabricated under same conditions, except for the photoelectrode utilized.