Highly conductive ion tracks in tetrahedral amorphous carbon by irradiation with 30 MeV C<sub>60</sub>projectiles

Krauser, J.; Nix, Anne-Katrin; Gehrke, Hans-Gregor; Hofsäß, H.; Trautmann, C.; Weidinger, A.

doi:10.1088/1367-2630/13/8/083023

Cited by 7 publications

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“…16 The onset of conducting track formation occurs around 20-30 keV/nm and the highest track conductivities are obtained for maximum achievable electronic energy loss of about 40 keV/nm for 1GeV 238 U ions or 72 keV/nm for 30 MeV C 60 cluster ions. 17 Until now, beside ta-C conductive ion track formation was only observed in fullerene films.…”

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confidence: 99%

Tuning the conductivity of vanadium dioxide films on silicon by swift heavy ion irradiation

et al. 2011

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We demonstrate the generation of a persistent conductivity increase in vanadium dioxide thin films grown on single crystal silicon by irradiation with 1 GeV 238U swift heavy ions at room temperature. VO2 undergoes a temperature driven metal-insulator-transition (MIT) at 67 °C. After room temperature ion irradiation with high electronic energy loss of 50 keV/nm the conductivity of the films below the transition temperature is strongly increased proportional to the ion fluence of 5·109 U/cm2 and 1·1010 U/cm2. At high temperatures the conductivity decreases slightly. The ion irradiation slightly reduces the MIT temperature. This observed conductivity change is persistent and remains after heating the samples above the transition temperature and subsequent cooling. Low temperature measurements down to 15 K show no further MIT below room temperature. Although the conductivity increase after irradiation at such low fluences is due to single ion track effects, atomic force microscopy (AFM) measurements do not show surface hillocks, which are characteristic for ion tracks in other materials. Conductive AFM gives no evidence for conducting ion tracks but rather suggests the existence of conducting regions around poorly conducting ion tracks, possible due to stress generation. Another explanation of the persistent conductivity change could be the ion-induced modification of a high resistivity interface layer formed during film growth between the vanadium dioxide film and the n-Silicon substrate. The swift heavy ions may generate conducting filaments through this layer, thus increasing the effective contact area. Swift heavy ion irradiation can thus be used to tune the conductivity of VO2 films on silicon substrates

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Section: Introductionmentioning

confidence: 99%

Tuning the conductivity of vanadium dioxide films on silicon by swift heavy ion irradiation

et al. 2011

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“…However, even the distribution around the equilibrium charge state values leads to a distribution in electronic energy loss possibly resulting in significant distribution of individual track conductivities an may also influence the hillock formation process. [20][21][22][23][24] Additional irradiations were performed at CSNSM Orsay with 12 and 30 MeV C 60 cluster projectiles.…”

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Nano-hillock formation in diamond-like carbon induced by swift heavy projectiles in the electronic stopping regime: Experiments and atomistic simulations

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et al. 2012

Applied Physics Letters

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The formation of surface hillocks in diamond-like carbon is studied experimentally and by means of large-scale molecular dynamics simulations with 5 Â 10 6 atoms combined with a thermal spike model. The irradiation experiments with swift heavy ions cover a large electronic stopping range between $12 and 72 keV/nm. Both experiments and simulations show that beyond a stopping power threshold, the hillock height increases linearly with the electronic stopping, and agree extremely well assuming an efficiency of approximately 20% in the transfer of electronic energy to the lattice. The simulations also show a transition of sp 3 to sp 2 bonding along the tracks with the hillocks containing almost no sp 3 contribution. V

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“…However, the doping also increases the zero-field conductivity resulting in a weaker contrast between the track and matrix. The data are interpreted within the socalled 'barrier model' where the electrons are assumed to move fairly freely in well-conducting sp 2 regions but encounter barriers in track sections consisting of more sp 3 -like bonds.Earlier experimental work focussed mainly on the improvement of the track conductivity by changing experimental conditions (Zollondz et al 2006, Nix et al 2007, Krauser et al 2011, 2013. The most important parameter for high conductance is the specific energy loss of the ions.…”

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confidence: 99%

“…Earlier experimental work focussed mainly on the improvement of the track conductivity by changing experimental conditions (Zollondz et al 2006, Nix et al 2007, Krauser et al 2011, 2013. The most important parameter for high conductance is the specific energy loss of the ions.…”

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Electrical conduction of ion tracks in tetrahedral amorphous carbon: temperature, field and doping dependence and comparison with matrix data

et al. 2015

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This paper gives an extended overview of the electrical properties of ion tracks in hydrogen-free tetrahedral amorphous carbon (ta-C) with a sp 3 bond fraction of about 80%. The films were grown by mass selected ion beam deposition of 100 eV 12 C + ions. The ion tracks are generated by irradiation of ta-C films with uranium ions of 1 GeV kinetic energy. Along the ion path a conversion from diamondlike (sp 3 ) carbon to graphite-like (sp 2 ) carbon takes place. Topography and current measurements of individual ion tracks were performed by atomic force microscopy at ambient temperature. The temperature dependence of the electric conductivity was studied between 15 and 390 K by means of 0.28 mm 2 large contact pads averaging over about 10 7 tracks. For each sample and at each temperature the conductivity as a function of the applied electrical field (non-ohmic behaviour) was measured separately and the data were extrapolated to field zero. In this way, the zero-field conductivity was determined independent from the field dependence. In spite of large differences in the absolute values, the temperature dependence of the zero-field conductivities is found to be very similar in shape for all samples. The conductivities follow a T 1 4 -/ law up to temperatures slightly below room temperature.At higher temperatures a transport mechanism based on over-barrier hopping dominates with an activation energy of about 220 meV for tracks and 260 meV for the ta-C matrix. The field dependence measurements show that the deviation of the I-V characteristics from ohmic behaviour decreases with increasing zero-field conductivity. We also tested Cu-doped ta-C samples and found that they conduct significantly better than pure ta-C. However, the doping also increases the zero-field conductivity resulting in a weaker contrast between the track and matrix. The data are interpreted within the socalled 'barrier model' where the electrons are assumed to move fairly freely in well-conducting sp 2 regions but encounter barriers in track sections consisting of more sp 3 -like bonds.Earlier experimental work focussed mainly on the improvement of the track conductivity by changing experimental conditions (Zollondz et al 2006, Nix et al 2007, Krauser et al 2011, 2013. The most important parameter for high conductance is the specific energy loss of the ions. Only very heavy ions with energies of several 100 MeV create well-conducting tracks. Controlled doping of the ta-C matrix yielded also some improvement of the tracks (Nix 2010, Krauser et al 2012). The highest track conductivity (10 3 S m −1 ) measured so far was obtained in a 1 at.% Fe-doped ta-C film irradiated with C 60 cluster ions (Krauser et al 2013). Among the monoatomic projectiles 1 GeV uranium ions are the most suited particles due to their high energy loss in ta-C of dE/dx∼40 keV nm −1 . This ion beam was also used in the present study.An important aspect is the behaviour of the conducting ion tracks under an applied electrical field. In most cases (see references in the preceding ch...

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Highly conductive ion tracks in tetrahedral amorphous carbon by irradiation with 30 MeV C₆₀projectiles

Cited by 7 publications

References 26 publications

Tuning the conductivity of vanadium dioxide films on silicon by swift heavy ion irradiation

Tuning the conductivity of vanadium dioxide films on silicon by swift heavy ion irradiation

Nano-hillock formation in diamond-like carbon induced by swift heavy projectiles in the electronic stopping regime: Experiments and atomistic simulations

Electrical conduction of ion tracks in tetrahedral amorphous carbon: temperature, field and doping dependence and comparison with matrix data

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Highly conductive ion tracks in tetrahedral amorphous carbon by irradiation with 30 MeV C60projectiles

Cited by 7 publications

References 26 publications

Tuning the conductivity of vanadium dioxide films on silicon by swift heavy ion irradiation

Tuning the conductivity of vanadium dioxide films on silicon by swift heavy ion irradiation

Nano-hillock formation in diamond-like carbon induced by swift heavy projectiles in the electronic stopping regime: Experiments and atomistic simulations

Electrical conduction of ion tracks in tetrahedral amorphous carbon: temperature, field and doping dependence and comparison with matrix data

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Highly conductive ion tracks in tetrahedral amorphous carbon by irradiation with 30 MeV C₆₀projectiles