A.S. Nemov

Study of near surface layer of graphite produced by nitrogen ion bombardment at high doses

To study the modified surface layers of graphites and deposited films of sputtered material, the dependences of sputtering yield Y , and ion-electron emission coefficient γ on ion incidence angle and target temperature under high dose 30 keV N+ 2 ion irradiation have been measured. In the angular range θ=0-80° Y and γ increase approximately as inverse cosθ, Y of POCO-AXF-5Q are 1.5 times larger than of MPG-LT. The dependences of γ (T) manifests a step-like behaviour typical for the radiation induced phase transitions. EPR analysis shows that at near room temperatures the point electron defects are typical of carbon and the defects due to carbon atoms interacting with 14 N nuclei. At elevated temperatures (≥ 300°C) there are the defects typical of graphite-like structures. The films deposited on glass collectors shows for cold targets only the defects typical of carbon, for the heated graphites - also the defects associated with C-14N nuclei interaction.

Regularities of Ion-Electron Emission of One-Dimensional Carbon-Based Composite Material

The temperature dependences of the ion-electron emission yield γ(T), the crystal structure, and morphology of a surface layer of a carbon-based KUP-VM composite material under high-dose irradiation with N2+ 30 keV ions have been investigated. The complex two-stage nature of the dependence γ(T) is caused by the processes of dynamic annealing of radiation damage in structural components of a composite material.

Effect of the ion current density on the temperature dependences of ion-induced electron emission from carbon-based materials

The effect of ion current density j on the temperature dependences of the ion-induced electron emission yield γ(T) of carbon-based materials (polycrystalline graphite MPG-8, highly oriented pyrolytic graphite UPV-1T, and some glassy carbons) under irradiation by atomic and molecular nitrogen ions with energies of several tens of keV has been experimentally studied. The most significant effect of the density j on the dependences γ(T) is observed for low-temperature glassy carbons.

Temperature dependences of the ion-electron emission of glassy carbons under 30-keV argon ion irradiation

The temperature dependences (−200°C < T ≤ 350°C) of the ion-induced electron emission yield γ and the structures of modified surface layers have been studied experimentally for SU-850, SU-1000, SU-1300, SU-2000, and SU-2500 glassy carbons under high-dose 30-keV Ar+ and N2+ ion irradiation. Glassy carbons manufactured using a relatively high heat-treatment temperature Tht exhibit a stepwise increase in the electron yield at certain annealing temperatures Ta. The same behavior is observed for graphitized carbon materials. For low-temperature glassy carbons, the electron yield exhibits a monotonic increase with increasing irradiation temperature. The observed differences are related to the occurrence of different structural types of fullerene-like nanoparticles in the low-and high-temperature glassy carbons.