Stopping powers and inelastic mean free path of 200Â eV-50Â keV electrons in polymer PMMA, PE, and PVC

The stopping power (SP) and inelastic mean free path (IMFP) of three polymers: polymethyl methacrylate (PMMA), polyethylene (PE), and polyvinyl chloride (PVC) for electron energies from 200 eV to 50 keV have been determined based on dielectric models. The energy loss function (ELF) is the main input in the calculation of the SP and IMFP for the dielectric models. ELF in this study was determined from a previously published quantitative analysis of reflection electron energy loss spectroscopy (REELS) spectra. The SP of PMMA, PE and PVC decreases and the IMFP increases with increasing electron energies up to 50 keV. For comparison, data from the National Institute of Standards and Technology (NIST) database for electron energies from 10 to 50 keV were used and show that SP in this study is lowered by 10-15%. The obtained IMFP for PE was compared with those calculated using the TPP2M predictive equations and shows that a reasonable agreement with a root-mean-square (rms) is 7.01 Å. The present approach has high potential for the experimental determination of SP and IMFP from the REELS spectra.