DETERMINATION OF THE INELASTIC MEAN FREE-PATH OF ELECTRONS IN GAAS AND INP AFTER SURFACE CLEANING BY ION-BOMBARDMENT USING ELASTIC PEAK ELECTRON-SPECTROSCOPY

The inelastic mean free path (IMFP) of electrons is an important mater ial parameter needed for quantitative AES, EELS and non-destructive de pth profiling, The distinction between the terms for IMFP and the atte nuation length (AL) has been established by ASTM standards. A practica l experimental method for determining values of the IMFP is elastic pe ak electron spectroscopy (EPES). In this method, experimentally determ ined ratios of elastically backscattered electrons from test surfaces and from a Ni reference standard are compared with the values evaluate d theoretically, The present paper reports systematic measurements of the IMFP by EPES for GaAs and InP, They are carried out in two laborat ories using two different electron spectrometers: a CMA in Budapest an d DCMA in Warsaw, Prior to measurements, the samples were amorphized b y high-energy Ar+ ions (100-400 keV), and the surface composition was determined by quantitative XPS. Argon cleaning produces enrichment of samples in the surface layer in Ga (70%) and In (70%), respectively, T he experiments refer to a such modified sample surface that was consid ered in Monte Carlo calculations, The experimental data were analyzed using calibration curves from Monte Carlo calculations which account f or multiple elastic scattering events. This approach has been used pre viously for elemental solids and is now extended to amorphized binary compounds. The experimental values of IMFP obtained in both laboratori es exhibited a reasonable agreement with the available literature data in the 0.1-3.0 keV energy range. With respect to the information dept h of EPES, the experimental results refer to the bulk composition with in a reasonable extent. (C) 1998 Elsevier Science B.V.