Biomedical subjects

Mark S Gudiksen

Publications and source records attributed to Mark S Gudiksen.

5 recordsLinked to original sources

PubMed2005

Single-crystalline vanadium dioxide nanowires with rectangular cross sections.

We report the synthesis of single-crystalline VO2 nanowires with rectangular cross sections using a vapor transport method. These nanowires have typical diameters of 60 (+/-30) nm and lengths up to >10 mum. Electron microscopy and diffraction measurements show that the VO2 nanowires are single crystalline and exhibit a monoclinic structure. Moreover, they preferentially grow along the [100] direction and are bounded by the (01) and (011) facets. These VO2 nanowires should provide promising materials for fundamental investigations of nanoscale metal-insulator transitions.

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PubMed2005

Electroluminescence from a single-nanocrystal transistor.

We report the fabrication and characterization of light-emitting transistors incorporating individual cadmium selenide (CdSe) nanocrystals. Electrical measurements conducted at low bias voltage and low temperature show clear evidence of Coulomb blockade behavior, indicating that electrons pass through the nanocrystal by single-electron tunneling. Once the bias voltage exceeds the band gap of CdSe, devices with asymmetric tunnel barriers emit linearly polarized light. Combined analyses of the electrical and optical data indicate that the tunnel couplings between the nanorod and the metallic electrodes change significantly as a function of bias voltage and light emission results from the inelastic scattering of tunneling electrons.

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PubMed2004

Semiconductor nanowire heterostructures.

Recent progress on the synthesis and characterization of semiconductor nanowire heterostructures is reviewed. We describe a general method for heterostructure synthesis based on chemical vapour deposition and the vapour-liquid-solid growth of crystalline semiconducting nanowires. We then examine examples of nanowire heterostructures for which physical properties have been measured, considering the effects of synthetic conditions on the heterointerfaces as well as the electrical and optical characterization measurements that reveal heterointerface formation and quality. Finally, we identify areas of technical and conceptual progress that can contribute to the development of functional nanowire heterostructures.

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PubMed2002

Epitaxial core-shell and core-multishell nanowire heterostructures.

Semiconductor heterostructures with modulated composition and/or doping enable passivation of interfaces and the generation of devices with diverse functions. In this regard, the control of interfaces in nanoscale building blocks with high surface area will be increasingly important in the assembly of electronic and photonic devices. Core-shell heterostructures formed by the growth of crystalline overlayers on nanocrystals offer enhanced emission efficiency, important for various applications. Axial heterostructures have also been formed by a one-dimensional modulation of nanowire composition and doping. However, modulation of the radial composition and doping in nanowire structures has received much less attention than planar and nanocrystal systems. Here we synthesize silicon and germanium core-shell and multishell nanowire heterostructures using a chemical vapour deposition method applicable to a variety of nanoscale materials. Our investigations of the growth of boron-doped silicon shells on intrinsic silicon and silicon-silicon oxide core-shell nanowires indicate that homoepitaxy can be achieved at relatively low temperatures on clean silicon. We also demonstrate the possibility of heteroepitaxial growth of crystalline germanium-silicon and silicon-germanium core-shell structures, in which band-offsets drive hole injection into either germanium core or shell regions. Our synthesis of core-multishell structures, including a high-performance coaxially gated field-effect transistor, indicates the general potential of radial heterostructure growth for the development of nanowire-based devices.

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PubMed2002

Growth of nanowire superlattice structures for nanoscale photonics and electronics.

The assembly of semiconductor nanowires and carbon nanotubes into nanoscale devices and circuits could enable diverse applications in nanoelectronics and photonics. Individual semiconducting nanowires have already been configured as field-effect transistors, photodetectors and bio/chemical sensors. More sophisticated light-emitting diodes (LEDs) and complementary and diode logic devices have been realized using both n- and p-type semiconducting nanowires or nanotubes. The n- and p-type materials have been incorporated in these latter devices either by crossing p- and n-type nanowires or by lithographically defining distinct p- and n-type regions in nanotubes, although both strategies limit device complexity. In the planar semiconductor industry, intricate n- and p-type and more generally compositionally modulated (that is, superlattice) structures are used to enable versatile electronic and photonic functions. Here we demonstrate the synthesis of semiconductor nanowire superlattices from group III-V and group IV materials. (The superlattices are created within the nanowires by repeated modulation of the vapour-phase semiconductor reactants during growth of the wires.) Compositionally modulated superlattices consisting of 2 to 21 layers of GaAs and GaP have been prepared. Furthermore, n-Si/p-Si and n-InP/p-InP modulation doped nanowires have been synthesized. Single-nanowire photoluminescence, electrical transport and electroluminescence measurements show the unique photonic and electronic properties of these nanowire superlattices, and suggest potential applications ranging from nano-barcodes to polarized nanoscale LEDs.

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