Nanowires electronic properties

Talapin, D. V. Black, C. T. Kagan, C. R. Shevchenko, E. V. Afzali, A. Murray, C. B. 2007. Alignment, electronic properties, doping, and on-chip growth of colloidal PbSe nanowires. J. Phys. Chem. C (in press). 

Figure 11.2. Nanowire electronic and optical properties, (a) Schematic of an NW-FET used to characterize electrical transport properties of individual NWs. (inset) SEM image of an NW-FET two metal electrodes, which correspond to source and drain, are visible at the left and right sides of the image, (b) Current versus voltage for an n-type InP NW-FET. The numbers inside the plot indicate the corresponding gate voltages (Vg). The inset shows current versus Vg for Fsd of 0.1 V. (c) Real-color photoluminescence image of various NWs shows different color emissions, (d) Spectra of individual NW photoluminescence. All NW materials show a clean band-edge emission spectrum with narrow FWHM around 20nm. (See color insert.)...

The fundamental physical properties of nanowire materials can be improved even more to surpass their bulk counterpart using precisely engineered NW heterostructures. It has been recently demonstrated that Si/Ge/Si core/shell nanowires exhibit electron mobility surpassing that of state-of-the-art technology.46 Group III-V nitride core/shell NWs of multiple layers of epitaxial structures with atomically sharp interfaces have also been demonstrated with well-controlled and tunable optical and electronic properties.47,48 Together, the studies demonstrate that semiconductor nanowires represent one of the best-defined nanoscale building block classes, with well-controlled chemical composition, physical size, and superior electronic/optical properties, and therefore, that they are ideally suited for assembly of more complex functional systems. 

The electronic states of nanowire systems exhibit a very different spectrum from that of bulk materials. In order to understand their unique electronic properties, we have modeled the band structure of these one-dimensional systems. 

In a nanowire system, the quantized subband energy enm and the transport effective mass mzz along the wire axis are the two most important parameters and determine almost all the electronic properties. Due to the anisotropic carriers and the special geometric configuration (circular wire cross section and high aspect ratio of length to diameter), several approximations were used in earlier calculations to derive e m and mzz in bismuth nanowires. In the... 

The tunable electronic properties of CNTs are being explored for next-generation IC architectures. As you may recall from Chapter 4, traditional Si-based microelectronic devices will likely reach a fundamental limit within the next decade or so, necessitating the active search for replacement materials. Accordingly, an area of intense investigation is molecular electronics - in which the electronic device is built from the placement of individual molecules.Not surprisingly, the interconnects of these devices will likely be comprised of CNTs and other (semi)conductive ID nanostructures such as nanowires. 

Nanometer-Sized Electronic Devices The possible use of carbon nanotubes in nanoelectronics has aroused considerable interest. Dramatic recent advances have fueled speculation that nanotubes (SWNTs) will be useful for downsizing circuit dimensions. Because of their unique electronic properties, SWNTs can be interfaced with other materials to form novel heterostructures [156]. The simplest device one can imagine with carbon nanotubes is that involving a bend or a kink, arising from the presence of a diametrically opposite pentagon-heptagon pair. The resultant junction connects two nanotubes of different chirality and hence of different electronic structure, leading to the realization of an intramolecular device. Such a device in SWNTs is found to behave like a diode rectifier [157]. Silicon nanowire-carbon nanotube heterojunctions do indeed exhibit a rectification behavior [158]. 

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