Attenuation of photoelectrons and Auger electrons leaving nickel deposited on a gold surface

Abstract

AbstractAttenuation lengths of signal electrons are very important in surface metrology. Contrary to inelastic mean free paths (IMFP), the attenuation length is determined by both inelastic and elastic scattering events of the signal electrons in the solid. Therefore, application of attenuation lengths leads to improved accuracy in measurements of length on a nanometer scale. In the present work, photoelectron and Auger‐electron spectra (AES) in regions of Au 4f, Ni 3p, Ni 2p, and Au MNN were recorded from nickel overlayers deposited in situ, step by step, on a gold surface. The experiment was coupled with advanced calculations of electron transport for the nickel/gold system. An overlayer growth mode has been elucidated by a line‐shape analysis of the Ni 2p spectra with the QUASES‐Tougaard software and from extensive Monte Carlo calculations of electron transport in the overlayer/substrate system with the SESSA software. The QUASES‐Tougaard analysis indicated three‐dimensional island growth followed by a continuous nickel overlayer for thicknesses exceeding 2 nm. The attenuation of electron intensities described by the effective attenuation length (EAL), calculated with the NIST SRD 100 database [Simulation of Electron Spectra for Surface Analysis (SESSA) software] and the NIST SRD 82 database, was found in close agreement for all electron transitions considered. The measured EAL values compared well with EALs calculated for Au 4f, Ni 3p, and Ni 2p photoelectrons, whereas the EAL derived from the measured Au MNN intensity–thickness plot was found to be about 20% less than the predicted values. Copyright © 2007 John Wiley & Sons, Ltd.