The implantation of 49BF2+ ions into evaporated amorphous films was investigated by using energies which ranged from 20 to 140keV. The implanted profiles were characterized by means of secondary ion mass spectrometry, and quantitative data on the first 4 moments of the profiles were gathered. The Pearson IV distributions and profiles which were calculated by using an Edgeworth expansion were fitted to the measured distributions by using an iterative procedure which used the profile moments as fitting parameters. The optimum set of parameter values was extracted for all of the implantation energies which were investigated, and both types of analytical function were found to provide an excellent fit to the experimental profiles at low energies. However, the Edgeworth expansion became less applicable above 100keV; where the stopping was predominantly electronic. The effect, upon the secondary ion mass spectrometry profiles, of primary sputtering O2+ ions was studied. In particular, a shallow distribution at 20keV was investigated. It was found that an energy of less than 5.5keV was required in order to minimize the broadening of the B tails towards greater depths. Monte Carlo simulations were performed by using 3 different versions of ion transport in matter, and various estimates for the electronic stopping cross-section. A comparison of the simulations and the secondary ion mass spectrometry profiles revealed large deviations from a velocity-proportional dependence of the electronic stopping cross-section at energies of less than 100keV. It was concluded that an improved theoretical model was required for the electronic interaction of low-velocity ions.

J.Tirén, B.G.Svensson: Journal of the Electrochemical Society, 1991, 138[2], 571-6