Transport and dielectric properties of thin fullerene (C₆₀) films (original) (raw)
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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.
Effect of oxygen on electric conductivities of C60 and higher fullerene thin films
Thin Solid Films, 2003
The dark conductivities and photoconductivities of C and higher fullerene (C , C , C and C) thin films in oxygen gas 60 70 76 78 84 at room temperature have been investigated. It was found that the time dependences of both the dark conductivities and photoconductivities of higher fullerene films are of the same pattern as those of a C film in oxygen gas. These electric 60 conductivities quickly decrease after the films are exposed to oxygen gas or air. Both the dark and photoconductivities of C and 60 C films are much higher than those of higher fullerene (C , C and C) films in vacuum. However, the dark conductivities 70 76 78 84 of these fullerene films after 24-h treatment in oxygen gas become of the same order of magnitude. The degree of reduction and saturation times of the electric conductivities of higher fullerene films in oxygen gas are smaller and longer, respectively, than those of C and C films.
Fullerene-60 thin films for electronic applications
Synthetic metals, 1999
Following the discovery of C 60 [1] and the subsequent developments, to produce purified bulky materials of C 60 [2], many interesting researches to discover the physical, optical, chemical and electronic properties of the material were carried out [3, 4]. Currently, electronic ...
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.
Cathodoluminescence studies of C60 fullerene-based films and nanostructures
Semiconductors, 2007
The objects of investigation in this work are the submicron C 60 fullerene-based films and fullerene nanostructures fabricated by electron beam lithography. The set of techniques for studying the fullerenes is extended due to attraction the spectral cathodoluminescence (CL) to either of initial fullerene films and submicron net structures with period about 0.9 µm, wall height 0.6 µm and width about 0.4 µm.
Computer simulation of fullerene-based ultra-low k dielectrics
Microelectronic Engineering, 2005
Three-dimensional fullerene based networks are proposed as new candidates for ultra-low k dielectric materials. C60 fullerene molecules are used as the nodes of the network. The nodes are connected by hydrocarbon chain molecules forming skeletons of simple cubic, face-centred-cubic or diamond-like symmetry. The structural units of the models consisting of two fullerenes and a hydrocarbon bridge molecule are optimised by means of quantum chemical methods. The density of local dipoles and electronic effects are considered to estimate the effective dielectric constant of the models. It is shown that k values of about 1.4 can be obtained if C 6 H 12 chain molecules are used to connect C60 molecules on a network with diamond-like symmetry.
Comparative study of optical parameters of fullerene C 60 film at different temperatures
Optics Communications, 2010
FullereneC 60 thin films on glass substrate (around 2000 thickness) were prepared by thermal evaporation technique. The structural, Surface morphology and optical properties of the film were studied. Optical properties in the spectral range 200 nm to 900 nm of Fullerene C 60 film is investigated by spectrophotometer at different temperature i.e.; room temperature and liquid nitrogen temperature (77K). Optical band gap at room temperature is found to be 2.30 eV, which goes on decreasing and reaches to 2.27 at 77K. Result indicates that C 60 film become more conducting at low temperature. Thickness and refractive index of film was calculated by ellipsometry. From the X ray analysis we have calculated the grain size, dislocation density, number of crystallite per unit area, and strain of the film. The surface morphology of film was analyzed by scanning electron microscope (SEM).
Diffusion processes for doping of C60 (fullerene) thin films
Solar Energy Materials and Solar Cells, 2003
As part of our ongoing research program to produce a high-efficiency, low-cost, photovoltaic cell based on the fullerene C 60 , we report here on our first attempts at the intercalative doping of C 60 thin films by the electrodiffusion of metals. Semiconductor behavior with decreased values of conductivity activation energy has been demonstrated for the doped samples. The results are explained by electrodiffusion of Au from an electrode, dominated by grain boundary diffusion. r 0927-0248/03/$ -see front matter r 2002 Published by Elsevier Science B.V. PII: S 0 9 2 7 -0 2 4 8 ( 0 2 ) 0 0 1 9 1 -5
Monte Carlo simulation of electric conductivity for pure and doping fullerene (C60)
Physics Letters A, 2019
In this paper, we have used Monte Carlo (MC) method to simulate and study the temperature and doping effects on the electric conductivity of fullerene (C60). The results show that the band gap has reduced by the doping and the charge carrier transport is facilitated from valence band to conduction band by the temperature where is touched a 300 K. In this case, the conductivity reached a value of 4 × 10 −7 S cm −1. The electric conductivity of C60 can increase by the triphenylmethane dye crystal violet (CV) alkali metal to reach 4 × 10 −3 S cm −1 at 303 K. Our results of MC simulation have a good agreement with those extracted from literature [10,33].
Thin Solid Films, 2012
Among an extremely large number of possible fullerene applications in the field of electronics, optics and photovoltaics, C 60 -cages are also considered as a promising dopant for low dielectric constant (low-k) materials. In this study, we incorporated C 60 species into a 3aminopropyltrimethoxysilane (APTMS) based material. We prepared thin films by spin coating. Using X-ray photoelectron spectroscopy we analyzed the time-related interactions between the components of the prepared samples and the influence of the C 60 replacement by its better soluble derivative [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) on the chemical properties of the material. We applied atomic force microscopy to investigate the surface texture and thicknesses of the obtained films. In order to obtain information concerning the electrical properties of the material we performed capacitance-voltage characterization. We have proven that the increase of C 60 species realized by PCBM incorporation within the APTMS-based matrix reduces the dielectric constant of the examined films while preserving its homogeneity.