The simulation of SIMS measurements of light element profiles in diamond

Information about concentrations and profiles of impurities on or near surf aces is commonly obtained from secondary ion mass spectroscopy (SIMS) measu rements. These may, however, yield misleading results when sharp profiles a re measured. In this work, the results of computer simulations of SIMS meas urements of light impurities (hydrogen, deuterium and lithium) on diamond a re presented, using a modified version of the transport of ions in matter ( TRIM) computer code which has been extended to include the continuously cha nging material during the SIMS profiling. The simulations show that elastic recoils, induced by the probing beam used in SIMS, can broaden an initiall y sharp profile and thus induce an apparent diffusion profile. The changes in matrix composition caused by the implantation of the probing beam can mo dify the depth scale. These are demonstrated by performing detailed computations for the technolo gically important cases of (i) a hydrogen-passivated diamond surface and (i i) a thin Li layer on top of a diamond surface. The results show that the e xponential tail, experimentally measured by SIMS and interpreted as being d ue to diffusion of Li into diamond, can be fully explained by the art-effec t of the SIMS measurement. Very good agreement between the simulated and me asured SIMS profiles is obtained when it is assumed that Li is present only on the surface as a thin layer. (C) 2000 Elsevier Science B.V. All rights reserved.