N A Pradhan | PubMed Health

PubMed2005

Atomic scale conductance induced by single impurity charging.

A scanning tunneling microscope was used to probe electron transport through an alkali doped C(60) monolayer crystal on Al(2)O(3) grown by the oxidation of NiAl(110). Each individual alkali atom forms a localized complex with the neighboring C(60) molecules. Charging of the complex induces a substantial rise in the current that persists outside the physical dimensions of the complex. This induction of the current rise is characterized by spatially resolved spectroscopy and mapping of the differential conductance (dI/dV) in the vicinity of the complex.

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PubMed2004

Vibronic states in single molecules: C60 and C70 on ultrathin Al2O3 films.

Vibronic states are observed in single C(60) and C(70) molecules by scanning tunneling microscopy. When single fullerene molecules are adsorbed on a thin layer of Al(2)O(3) grown on a NiAl(110) substrate, equally spaced features are observed in the differential conductance (dI/dV), which are clearly resolved in d(2)I/dV(2) spectra. These features are attributed to the vibronic states of the molecule. The vibronic progressions are sensitive to the molecular orientations and can have different spacings in different electronic bands of the same molecule. For C(60,) these vibronic states are associated with the intramolecular A(g) and H(g) vibrational modes. Vibronic states are not resolved in molecules adsorbed on the metal surface. However, inelastic electron tunneling spectroscopy exhibits a vibrational mode at 64 meV for C(60) and 61 meV for C(70) adsorbed on NiAl(110).

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