The data treatment influence on the spectra decomposition in positron lifetime spectroscopy Part 1: On the interpretation of multi-component analysis studied by Monte Carlo simulated model spectra

We investigate the decomposability of multi-component positron lifetime spectra generated by Monte Carlo simulations. For improving the stability of the decomposition of lifetime spectra, it is better to collect more counts instead of reducing the size of the scintillators or narrowing the energy windows, i.e. improving the resolution of the spectrometer. Good statistics improves the decomposability for small trapping rates, i.e. small intensities, of the defect lifetimes. Decompositions consisting of too few components lead to intermediate lifetimes. These lifetimes are not present in the original spectrum but give the best fit in non-linear regression. From the difference in variance between, e.g., two- and three-component fits together with a comparison between the bulk lifetime measured as a reference spectrum and that calculated from experimental data one can decide which number of components should be right. In the case of shallow traps in semiconductors we verified that the decrease of the longer lifetime τ2 with lower temperature is an artifact of the two-component decomposition of real three-component spectrum.