Cs+ depth profile analysis of Si at high incidence angles is plagued by additional transient effects which extend transient widths to values similar to10 x greater than that expected from those obtained at lower incidence angles. This study examines the conditions (primary ion energy and incidence angle) at which these enhanced, transient effects are first noted. This is carried out through measurement of Si-profiles (collected on both PHI Adept and PHI 6600 SIMS instruments) over the 250 eV to 5 keV primary ion energy range from Si wafers terminated with an similar to1 nm native oxide. The resulting data set allows for the conditions under which these effects occur to be mapped out and for an equation describing the dependence on the primary ion energy and incidence angle to be derived. (C) 2002 Elsevier Science B.V. All rights reserved.