TPP-2M formula EDAC

This "TPP-2M" formula for estimating electron inelastic mean free paths (IMFPs) has been proposed by Tanuma, Powell, and Penn (see Tanuma, Powell, and Penn, Surf. and Interface Anal. 17, 927 (1991); Tanuma, Powell, and Penn, Surf. Interface Anal. 21, 165 (1994); S. Tanuma, C. J. Powell, and D. R. Penn, Surf. Interface Anal. 21, 165 (1994); and C. J. Powell and A. Jablonski, J. Phys. Chem. Ref. Data 28, 19 (1999) and Surf. and Interface Anal. 29, 108 (2000)). The TPP-2M formula is derived from fits to IMFPs that were calculated for many solids from optical data. The formula can thus be used to estimate IMFPs for any solid material for which certain physical parameters are known or can be reasonably estimated.

The main parameters in this formula are

Note that the IMFP as appropriate to a photoelectron diffraction calculation is not necessarily equal to the effective attenuation length (EAL), with the latter also including elastic scattering effects such as those involved in photoelectron diffraction (see e.g. Jablonski and Powell, J. Electron Spect. 98-99, 1 (1999) and 100, 137 (1999)).

Lastly, IMFP and EAL data for solid elements and compounds can be obtained from databases available without charge from the National Institute for Standards and Technology via The IMFP data should be used whenever possible for the IMFP inputs to this program.