Effect of oxygen on electric conductivities of C60 and higher fullerene thin films (original) (raw)

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Dark- and photo-conductivity measurements on films of fullerene C60

Il Nuovo Cimento D, 1998

Thin-film samples have been prepared by evaporating a commercial fullerene C 60 powder from a tungsten crucible, at a pressure of 10-5 Pa on to quartz or Corning glass substrates. Samples were equipped with coplanar Cr-Au electrodes evaporated onto the surface of the film. Dark-conductivity measurements in the range 300-600 K evidence the existence of hysteresis phenomena. Thermal annealing influences photoconductivity and changes the power coefficient in the power law illumination-intensity dependence of photoconductivity. The influence of oxygen adsorbed in the film matrix on the electrical properties and on the density of states is discussed. A tentative for explaining the photoconductivity-light-intensity dependence has been done assuming a continuous density-of-state distribution in the energy gap of the semiconductor. PACS. 72.40 -Photoconduction and photovoltaic effects. PACS 72.20. -Conductivity phenomena in semiconductors and insulators.

Linear electronic and optical processes in Fullerene thin films

2005

The electrical properties of C60 have been extensively studied in both the solid and solution phases. The vibrational spectroscopy of C60 is predominantly molecular in character. However electronic spectroscopy reveals features, which are specific to the solid. These features have been attributed to intermolecular charge transfer states. The relative importance of these inter- and intramolecular processes in terms of their contribution to the electronic transport is discussed. Cyclic voltammetry is employed to generate charged molecular species, which also contribute to the conduction process and comparisons to optical excited states species are drawn. The cyclic voltammetry was monitored in situ with vibrational spectroscopy so as to observe any shifts in the C60 spectrum due to charging. The current voltage characteristics of thin film sandwich structures fabricated by vacuum are then presented and discussed. A strongly non-linear behaviour is observed, a sharp increase in the device conductance being observed at relatively low voltages at both room temperature and at 20K. The room temperature IV curves confirm a lattice collapse upon charging. The high conductivity state is however observed to be stable at low temperature.

Transport and dielectric properties of thin fullerene (Cā‚†ā‚€) films

1996

Dielectric behavior of pristine and modified fullerene (C 6 0) films was investigated over the frequency range of 0.5 mHz to 100 kHz. The presence of mobile ions in the large interstitial spaces of the C 6 0 lattice compromises the breakdown voltage and makes pure C 60 unsuitable for applications requiring high-quality dielectric films (such as microelectronic applications). However, various immobile ions or neutral species (e.g., oxygen) can be made to fill the interstitial volume, changing the characteristics of the 2.

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