The size dependence of tin oxide atomic cluster nanowire field effect transistors

Electrical observation of sub-band formation in SnO2 nanobelts

The electrical observation of energy sub-band formation in the electronic structure, that gives rise to the phenomenon of quantized transport is reported in tin oxide (SnO2) nanobelt back-gate field-effect transistors, at low temperatures. Sub-band formation was observed as current oscillations in the drain current vs. gate voltage characteristics, and was analyzed considering the nanobelt as a "quantum wire" with a rectangular cross-section and hard walls. The lateral quantum confinement in the nanowires created conditions for the successive filling of the first twelve electron energy sub-bands, as the gate voltage increases. When the source-drain voltage is changed, the oscillations are not dislocated with respect to the gate voltage indicating flat-band energies, and that the observations are incompatible with the phenomena of Coulomb blockade and tunnelling oscillations. The separation of the energy sub-bands was found to be in good agreement with the measured cross-section dimensions of the nanobelt and with the threshold temperature, since for T > 60 K the oscillations tend to vanish.

Fractal electronic devices: simulation and implementation

Many natural structures have fractal geometries that exhibit useful functional properties. These properties, which exploit the recurrence of patterns at increasingly small scales, are often desirable in applications and, consequently, fractal geometry is increasingly employed in diverse technologies ranging from radio antennae to storm barriers. In this paper, we explore the application of fractal geometry to electrical devices. First, we lay the foundations for the implementation of fractal devices by considering diffusion-limited aggregation (DLA) of atomic clusters. Under appropriate growth conditions, atomic clusters of various elements form fractal patterns driven by DLA. We perform a fractal analysis of both simulated and physical devices to determine their spatial scaling properties and demonstrate their potential as fractal circuit elements. Finally, we simulate conduction through idealized and DLA fractal devices and show that their fractal scaling properties generate novel, nonlinear conduction properties in response to depletion by electrostatic gates.

Directed Self-Assembly: Expectations and Achievements

Nanotechnology has been a revolutionary thrust in recent years of development of science and technology for its broad appeal for employing a novel idea for relevant technological applications in particular and for mass-scale production and marketing as common man commodity in general. An interesting aspect of this emergent technology is that it involves scientific research community and relevant industries alike. Top-down and bottom-up approaches are two broad division of production of nanoscale materials in general. However, both the approaches have their own limits as far as large-scale production and cost involved are concerned. Therefore, novel new techniques are desired to be developed to optimize production and cost. Directed self-assembly seems to be a promising technique in this regard; which can work as a bridge between the top-down and bottom-up approaches. This article reviews how directed self-assembly as a technique has grown up and outlines its future prospects.

Diameter-engineered SnO2 nanowires over contact-printed gold nanodots using size-controlled carbon nanopost array stamps

A novel and effective methodology to control the diameters of semiconductor nanowires is reported through a versatile contact-printing method for obtaining size-controlled nanocatalysts by size-tunable carbon-based nanometer stamps. Vertically aligned carbon nanopost arrays, derived from nanoporous alumina templates, are used as the nanoscale stamps for printing of catalyst nanoparticles. The diameter of the carbon nanopost can be engineered by adjusting the pore dimension of the templates. Over the contact-printed Au nanodots in a uniform size distribution, semiconductor SnO2 nanowires are grown via a vapor-liquid-solid growth mechanism. Consequently, a direct dimension correspondence is achieved between the carbon nanopost stamp, the printed Au catalyst, and the finally obtained SnO2 nanowires. A model example of the diameter-dependent electrical properties of the semiconductor nanowires is successfully demonstrated in this work by applying three diameter-controlled SnO2 nanowires to nanowire field effect transistors.