The relation between the electron energy loss spectra of hafnia and its dielectric function

Recently two papers have been published deriving the dielectric function from hafnia from electron energy loss data (Jin et al. Applied Physics Letters 100 083713 (2006), Behar et al. Phys. Rev A. 80 062901 (2009)). The obtained dielectric functions are compared in their optical limit and differ considerably. Here we try to clarify the situation by presenting new experimental data and review the analysis procedure used in the earlier work. We conclude that the discrepancy is most likely caused by a shortcoming in the way that the momentum-dependence of the dielectric function is modelled.