Study of ion emission from a germanium crystal surface under impact of fast Pb ions in channeling conditions

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS

卷:267

Article; Proceedings Paper

L'Hoir, A.¹  Koumeir, C.²  Della Negra, S.³  Boduch, P.⁴  Roussel-Chomaz, P.⁵  Cassimi, A.⁴  Chevallier, M.²  Cohen, C.¹  Dauvergne, D.²  Fallavier, M.²  Jacquet, D.³  Manil, B.⁴  Poizat, J. -C.²  Ray, C.²  Rothard, H.⁴  Schmaus, D.¹  Toulemonde, M.⁴ 

[1] Univ Paris 06, Inst NanoSci Paris, UMR CNRS 7588, F-75015 Paris, France

[2] Univ Lyon 1, Inst Phys Nucl Lyon, CNRS, IN2P3, F-69622 Villeurbanne, France

[3] Univ Paris 11, Inst Phys Nucl Orsay, CNRS, IN2P3, F-91406 Orsay, France

[4] CEA, Ctr Rech Ions Mat & Photon, UMR 6637, CNRS, F-14040 Caen, France

[5] GANIL, F-14076 Caen 5, France

关键词: Channeling;    Sputtering;    Ion emission;    Heavy ions;    Electronic energy deposition;    Charge state;   

DOI  :  10.1016/j.nimb.2009.02.041

来源: Elsevier

【 摘 要 】

A thin germanium crystal has been irradiated at GANIL by Pb beams of 29 MeV/A (charge state Q(in) = 56 and 72) and of 5.6 MeV/A (Q(in), = 28). The induced ion emission from the sample entrance surface was studied, impact per impact, as a function of Q(in) velocity v(in) and energy loss Delta E in the crystal. The Pb ions transmitted through the crystal were analyzed in charge (Q(out),) and energy using the SPEG spectrometer. The emitted ionized species were detected and analyzed in mass by a time-Of-flight multianode detector (LAG). Channeling was used to select peculiar Delta E values in Ge and hence peculiar Pb ion trajectories close to the emitting entrance surface. The experiment was performed in standard vacuum. No Ge emission was found. The dominating emitted species are H+ and hydrocarbon ions originating from the contamination layer on top of the crystal. The mean value (M) of the number of detected species per incoming Pb ion (multiplicity) varies as (Q(in)/v(in))(p), with p values in agreement with previous results. We have clearly observed an influence of the energy deposition Delta E in Ge on the emission from the top contamination layer. When selecting increasing values of Delta E, we observed a rather slow increase of M). On the contrary, the probabilities of high multiplicity values, which are essentially connected to fragmentation after emission, strongly increase with Delta E. (C) 2009 Elsevier B.V. All rights reserved

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