ELF dielectric functions for various materials.
Authors/Creators
- 1. Université libre de Bruxelles, Service de Métrologie Nucléaire , 50 av. F. D. Roosevelt, Belgium
- 2. Inst. de Ciencia de Materiales de Sevilla, Isla de la Cartuja, E-41092 Sevilla, Spain
- 3. Dept of Physics, Chemistry, and Pharmacy, University of Southern Denmark, DK-5230 Odense M, Denmark
Description
Data for the energy loss function (ELF) of selected materials compiled from various publications.
The imaginary part of the inverse of the dielectric function, Im{−1/ε(k,hω)}, denoted the energy loss function (ELF), is the leading function that describes the material response to account for energy losses of swift electrons in matter. For this reason, it is a practical advantage to express the dielectric function in the form of a parametrized ELF, instead of the dielectric function itself, as input for the calculation of inelastic scattering cross sections. Here the ELF is expressed as a sum of Drude-Lindhard type oscillators (see e.g. Yubero F, Sanz JM, Ramskov B, Tougaard S. Model for quantitative analysis of reflection-electron-energy-loss spectra: Angular dependence. Phys Rev B. 1996;53:9719-9727)
The ELF data describe the dielectric properties of materials.
It may be applied to calculate energy loss processes of fast electrons moving in a material as well as in geometries met in REELS, XPS and AES where the effect of the surface and a static core hole are included (see e.g. QUEELS-software that can be downloaded at: doi: 10.5281/zenodo.6022426)
The data structure is:
For each material, a reference to the data for each material is given
After a line with @ , the ELF data follows in lines with the following meaning
1. Excitation parameters ac, bc to model core excitations (see Penn, J. Elec. Spectr., 9(1976)29).
When ac = 0.001 and bc = -2: no data was available.
2. Energy gap (eV)
3. Refractive Index
in the next lines, are the parameters for the oscillators: one line for each oscillator
4. energy position (eV), intensity (eV^2), width (eV), alpha
5.
6.
.
.
Examples of data files that can be directly read by QUEELS for Au and Si are seen in the files ELF_Au.txt and ELF_Si.txt respectively.