Computer simulations of positron-lifetime spectroscopy on thermally generated vacancies in copper and comparison with experimental results.

Abstract

Computer simulations of positron-lifetime spectra on thermally generated vacancies in copper have been carried out in order to separate possible artifacts of the analysis procedure from physical effects. We use experimental results of absolute vacancy concentration measurements and the conventional two-state trapping model to generate input parameters for the simulation. The computed spectra are analyzed by means of the programs positronfit and patfit/(hy88. The comparison of the input parameters with the fitted parameters demonstrates the validity of the fitting procedure for lifetimes greater than 40 ps. We have applied the simulation to the analysis of recent positron-lifetime measurements, which have shown a nonlinear temperature dependence of the calculated bulk lifetime in the vacancy region. It has been suggested that this nonlinearity could be an artifact of the fitting procedure. However, this study shows clearly that application of these fitting procedures to our simulated spectra produces no artifacts here; the output agrees with the input.