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

A. L’hoir , Charbel Koumeir (1) , S. Della Negra (2) , P. Boduch (3) , P. Roussel-Chomaz (4) , A. Cassimi (3) , Marius Chevallier (5) , C. Cohen (6) , D. Dauvergne (7) , M. Fallavier (7) , D. Jacquet (8) , B. Manil (9) , J.-C. Poizat , C. Ray , H. Rothard (3) , D. Schmaus , M. Toulemonde (3)

1 SUBATECH - Laboratoire SUBATECH Nantes
2 IPNO - Institut de Physique Nucléaire d'Orsay
3 CIMAP - UMR 6252 - Centre de recherche sur les Ions, les MAtériaux et la Photonique
4 CEA - Commissariat à l'énergie atomique et aux énergies alternatives
5 GEOLAB - Laboratoire de Géographie Physique et Environnementale
6 INSP - Institut des Nanosciences de Paris
7 IPNL - Institut de Physique Nucléaire de Lyon
8 Repmus - Représentations musicales
9 LPL - Laboratoire de Physique des Lasers

A thin germanium crystal has been irradiated at GANIL by Pb beams of 29 MeV/A (charge state Qin = 56 and 72) and of 5.6 MeV/A (Qin = 28). The induced ion emission from the sample entrance surface was studied, impact per impact, as a function of Qin, velocity vin and energy loss DE in the crystal. The Pb ions transmitted through the crystal were analyzed in charge (Qout) 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 DE in Ge and hence peculiar Pb ion trajectories close to the emitting 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 of the number of detected species per incoming Pb ion (multiplicity) varies as (Qin/vin)^p, with p values in agreement with previous results. We have clearly observed an influence of the energy deposition DE in Ge on the emission from the top contamination layer. When selecting increasing values of DE, we observed a rather slow increase of . On the contrary, the probabilities of high multiplicity values, that are essentially connected to fragmentation after emission, strongly increase with DE.

Keywords: material modification in semiconductors; ion sputtering; Channeling; ion emission

Domains: Atomic Physics [physics.atom-ph]

A. L’hoir, Charbel Koumeir, S. Della Negra, P. Boduch, P. Roussel-Chomaz, et al.. Study of ion emission from a germanium crystal surface under impact of fast Pb ions in channeling conditions. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2009, 267 (6), pp.876-880. ⟨10.1016/j.nimb.2009.02.041⟩. ⟨hal-00257795⟩