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ABSTRACT: We investigated the inner-sphere reorganization of ferrocene ((Cp) 2Fe ( n+ )) and tris(2,2'-bipyridine) iron ((bpy) 3Fe ( n+ )) in a single-molecule-transistor geometry. In (Cp) 2Fe ( n+ ) ( n = 0 and 1), almost no vibrations were excited during single-electron transport, whereas in (bpy) 3Fe ( n+ ) ( n = 1, 2, and 3), many distinct vibrations appeared, consistent with its larger reorganization energy. The observed excitation intensities varied significantly across devices, however, and could not be accounted for by "Franck-Condon" factors. This observation indicates that a quantitative account of electron-vibration coupling in single-electron tunneling requires further investigation.
Nano Letters 09/2008; 8(9):2963-7. · 13.20 Impact Factor
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ABSTRACT: We report the observation of a current-driven metal (M)-insulator (I) phase oscillation in two-terminal devices incorporating individual WxV1-xO2 nanobeams connected to parallel shunt capacitors. The frequency of the phase oscillation reaches above 5 MHz for approximately 1 mum long devices. The M-I phase oscillation, which coincides with the charging/discharging of the capacitor, occurs through the axial drift of a single M-I domain wall driven by Joule heating and the Peltier effect.
Nano Letters 03/2007; 7(2):363-6. · 13.20 Impact Factor
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ABSTRACT: We investigated the effect of substrate-induced strain on the metal-insulator transition (MIT) in single-crystalline VO(2) nanobeams. A simple nanobeam-substrate adhesion leads to uniaxial strain along the nanobeam length because of the nanobeam's unique morphology. The strain changes the relative stability of the metal (M) and insulator (I) phases and leads to spontaneous formation of periodic, alternating M-I domain patterns during the MIT. The spatial periodicity of the M-I domains can be modified by changing the nanobeam thickness and the Young's modulus of the substrate.
Nano Letters 11/2006; 6(10):2313-7. · 13.20 Impact Factor
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ABSTRACT: We report the synthesis of single-crystalline GeTe nanowires (NWs) and nanohelices (NHs) using a vapor transport method assisted by metal catalysts. The NWs have typical diameters of 65 +/- 20 nm and lengths reaching up to 50 mum, while NHs have an average helix diameter of 135 +/- 30 nm, with widely varying pitches. Electron microscopy and diffraction measurements show that these NWs and NHs are single crystalline and exhibit a rhombohedral structure. The devices incorporating individual GeTe NWs exhibit nonvolatile resistance changes associated with voltage-driven crystalline-amorphous transitions, suggesting that these NWs can be the basis of an electrically driven nonvolatile memory.
Journal of the American Chemical Society 07/2006; 128(25):8148-9. · 9.91 Impact Factor
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ABSTRACT: 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.
Journal of the American Chemical Society 01/2005; 127(2):498-9. · 9.91 Impact Factor
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ABSTRACT: We report a simple and reproducible method to fabricate two metallic electrodes made of different metals with a nanometer-sized gap. These electrodes are fabricated by defining a pair of gold electrodes lithographically and electrodepositing a second metal onto one of them. The method enables the fabrication of pairs of metallic electrodes that exhibit distinct magnetic properties or work functions. The utility of this technique is demonstrated by making single-electron tunneling devices incorporating 2-nm gold nanocrystals.
10/2003;
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ABSTRACT: We report the solution-based synthesis of single-crystalline nanorods composed of barium titanate (BaTiO3) and strontium titanate (SrTiO3), which yields well-isolated nanorods with diameters ranging from 5 to 60 nm and lengths reaching up to >10 mum. Electron microscopy and diffraction measurements show that these nanorods are composed of single-crystalline cubic perovskite BaTiO3 and SrTiO3 with a principal axis of the unit cell preferentially aligned along the wire length. These BaTiO3 and SrTiO3 nanorods should provide promising materials for fundamental investigations on nanoscale ferroelectricity, piezoelectricity, and paraelectricity.
Journal of the American Chemical Society 03/2002; 124(7):1186-7. · 9.91 Impact Factor
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ABSTRACT: We report scanned probe investigations on the ferroelectric properties of individual single-crystalline barium titanate nanowires. We show that nonvolatile electric polarization can be reproducibly induced and manipulated on these nanowires, thereby demonstrating that nanowires as small as 10 nm in diameter retain ferroelectricity. The coercive field for polarization reversal is determined to be 7 kV/cm, and the retention time for the induced polarization exceeds 5 days. These nanowires should provide promising materials for fundamental investigations on nanoscale ferroelectricity, and they may also be useful in nanoscale nonvolatile memory applications.
02/2002;
