Seminar at the Accelerator - Matter transformation induced by swift heavy ions ...
03.12.2012 - 03.12.2012
CMAM - Madrid
Informal seminars at the Accelerator


Speaker:  Marcel Toulemonde, IMAP-GANIL, Caen (Francia)

Title:  Matter transformation induced by swift heavy ions: Synergy between electronic and nuclear energy loss

Abstract: Experimental investigations with energetic heavy projectiles of sputtering of Ti and ion track formation in SiO2 whatever it is in crystalline or amorphous phase are examined in a beam energy range where nuclear and electronic energy losses are in competition. Using the catcher technique the total sputtering yield of Ti are measured in UHV apparatus leading to a sputtering rate larger than the TRIM-cascade [1]. It will be shown that it is an effect of the electronic energy loss but the quantification cannot be done without invoking that the inelastic thermal spike model acts in combination with the elastic collisions spike [2]. SiO2 quartz in its crystalline or amorphous phase was irradiated by Au ions between 500 keV and 10 MeV. For the crystalline phase channeling Rutherford Backscattering were used to characterize the induce damage and the damage versus fluence is fitted using an Avrami function (1-exp(-sFt)n), where s is the cross section, F the flux and t the time. The exponent n varies from 3.5 when the irradiation is performed in the pure nuclear energy regime to 1 for pure electronic energy regime. The deduced damage cross section seems to be constant within the beam energy range [3]. For the vitreous silica infra-red absorption is used to quantify the transformation of the vitreous quartz. The damage cross section is extracted using a Poisson law and the track radius is deduced, varying from 4.9 to 2.6 nm for Au beam energy from 0.5 MeV to 15 MeV [4]. Based on previous data where vitreous SiO2 was irradiated with much higher energy Au ions, the damage zone radius increases from 2.4 nm at 22.7 MeV to 5.4 nm at 168 MeV, and a U-shaped dependence on energy is observed is observed in the energy region from 0.3 to 168 MeV. In the transition regime where both nuclear and electronic energy loss are significant, a unified thermal spike model consisting of a coherent synergy of the elastic collision spike model with the inelastic thermal spike model is suggested to interpret and describe the radius evolution from the nuclear to the electronic energy regime in vitreous SiO2. This interpretation is confirmed by molecular dynamics calculation [5].

[1] J. P. Biersack and L. G. Haggmark Nucl. Instr. Meth 174 (1980) 257

[2] P. Sigmund and C. Claussen, J. Appl. Phys. 52 (1981) 990

[3] M. Toulemonde, S.M.M. Ramos, H. Bernas, C. Clerc, B. Canut, J. Chaumont and C. Trautmann Nucl. Instr. Meth. B 178 (2001) 331

[4] M. Toulemonde, W. J. Weber, G. Li, V. Shutthanandan, P. Kluth, T. Yang, Y. Wang and Y. Zhang Phys. Rev. B 83 (2011) 054106

[5] M. Backman, F. Djurabekova, O. H. Pakarinen, K. Nordlund, Y. Zhang, M. Toulemonde and W. J. Weber (2012) submitted


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