Nuclear Instruments & Methods in Physics Research B vol:261 issue:1-2 pages:512-515
With the implementation of low-energy time-of-flight Elastic Recoil Detection Analysis (ERDA), routine analysis of thin films with high depth resolution becomes possible. The optimization of the measurement conditions is a key issue for an accurate sample characterization and is normally a compromise among depth resolution, mass resolution and sensitivity, for a given sample. In this work, we focus on the depth resolution optimization, presenting an extensive study of two different materials, SiO2) and TiN, representative of light and medium mass targets. The film thickness varies between 10 and 50 nm. The samples were measured with different beams (Cl-35, Cu-63, Br-79 and I-127), energies (from 2 to 16 MeV) and incident angles. The experimental results are supported and generalized by simulations run with the Monte Carlo code MCERD. The different contributions of the system resolution, straggling and multiple scattering are evaluated and discussed. The best surface resolution is obtained in the low-energy limit. On the other hand, at low-energy the resolution deteriorates rapidly and better results for thicker films are obtained with higher incident energies. The loss of resolution with increasing depth is dominated by multiple scattering and becomes more relevant for heavy ions and heavy target atoms. In order to maintain a good depth resolution throughout the film, reducing the incident angle is more efficient than acting on the beam energy. (c) 2007 Elsevier B. V. All rights reserved.