Toward a better reliability in the deconvolution of SIMS depth profiles

In this paper, the problem of the deconvolution of SIMS depth profiles is a ddressed. In particular, the hypotheses that are necessary for the deconvol ution to be possible (in the actual state of the art) in the case of the SI MS signal are reviewed. Then, the principle of regularization, which is a m andatory step in the resolution of an id-posed problem, is clarified. Two r egularization methods used in the held of SIMS analysis are compared: Mille r regularization and maximum entropy regularization. In a second part the study of a possible deconvolution, using a depth resol ution function (DRF) that is not the DRF that has experimentally convolved the profile, is justified and theoretically addressed Two cases arise: the DRF used in tbe deconvolution process is either thinner than the experiment al DRF or it is thicker. It is shown that deconvolution using a DRF that is wider than the DRF that actually convolved tbe profile is possible, and mu st be taken into consideration. Some examples of simulated deconvolutions w ith a false DRF are given, and some tools are proposed that are theoretical ly able to detect a problem when the DRF used in the deconvolution process is wider than the real DRF. In the last section, an example of experimental deconvolution shows that th e deconvolution process is able to provide reliable information, In particu lar, deconvolution of a SIMS analysis conducted at 5.5 keV O-2(+) and 42.4 degrees incidence (in a Cameca IMS 3/4f) reveals some features of the sampl e that require at least 1 keV O-2(+) and 60 degrees primary beam incidence to be detected experimentally. (C) 1998 John Wiley & Sons, Ltd.