The role of a top oxide layer in cavities formed by MeV He implantation into Si C. Liu, E. Ntsoenzok, R. Delamare, D. Alquier and G. Regula Eur. Phys. J. AP, 23 1 (2003) 45-48 Published online: 12 June 2003 DOI: 10.1051/epjap:2003038