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- Popok, Vladimir, 1966, et al.
(författare)
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Conductance and EPR study of the endohedral fullerene Li@C60
- 2005
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Ingår i: Solid State Communications. ; 133:8, s. 499-503
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Tidskriftsartikel (refereegranskat)abstract
- Thin films and bulk samples of endohedral fullerenes Li@C60 are studied using current-voltage (I-V) measurements and electron paramagnetic resonance (EPR). Electrical measurements show a linear behaviour for the I-V curves and give an average resistivity of ca. 1.5 kOhmcm for thin Li@C60 films deposited in vacuum, four orders of magnitude lower than C60 samples. A drastic effect on the conductance, lowering it to the values typical for C60, is observed when the Li@C60 samples are exposed to ambient atmosphere. No additional paramagnetic centres (PCs) are found for the Li@C60 compared to C60 that can be related to the formation of dimers or trimers of the endohedral fullerene molecules. However, the presence of the Li atoms in the fullerene cages contributes to a change of the spin-spin and spin-lattice relaxation times. The spin-lattice relaxation time becomes 4 orders of magnitude longer compared to the spin-spin relaxation time.
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| 2. |
- Popok, Vladimir, 1966, et al.
(författare)
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Radiation-induced change of polyimide properties under high-fluence and high ion current density implantation
- 2004
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Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; A78:7, s. 1067-72
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Tidskriftsartikel (refereegranskat)abstract
- Polyimide (PI) films were implanted with 40-keV Ar+ and 80-keV Ar(2+) ions in a fluence range of 5.0*10^14-1.5*10^17 cm-2 at ion-current densities of 1-16 uA*cm2. It is shown that the conductivity of the samples rises with the ion-current density at a fixed fluence. Electrophysical parameters of the polyimide change stepwise with the implantation fluence when it exceeds a certain value. The change of electrical parameters of the implanted PI correlates with that of the optical and paramagnetic characteristics. The phenomenon of complete volatilisation of argon implanted with an energy of 40 keV due to surface heating and disordering under the high-power beam is found. It is shown that the change of ion charge and energy at constant beam-power density causes only a quantitative change in the polymer characteristics. A model of PI alteration and carbonised phase formation, taking into account the action of the high-power ion beam and the peculiarities of PI chemical structure, is developed to explain the observed effects. Implantation at high ion-current density can be suggested as an efficient practical means to control polymer conductivity and other parameters
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