Electron spectroscopy with Cr Kβ photons: high energy XPS and X-AES

Abstract

High energy XPS was used to measure electron attenuation lengths over a kinetic energy range of ∼2500 to ∼5900 eV. For these measurements the substrate overlayer method has been employed in conjunction with Cr K β ( hν =5946.7 eV) and synchrotron radiation ( hν =1800–4600 eV) excited XPS. Polyparaxylylene films were deposited ‘in situ’ on a gold substrate and the attenuation of the photoelectron signals from the Au 3s, 3d, 4p, 4d and 4f levels was monitored. The results were confirmed with similar measurements of the attenuation of the Au 4f substrate peaks excited by synchrotron radiation. It was found that the typical attenuation length at 5900 eV is 7.5 nm and over the measured energy range it follows an E 0.5 dependence in line with previous expectations. A set of 14 atomic sensitivity factors of a range of elements important for polymers and substrate standards as well as Auger parameters of several metals and alloys were measured using Cr K β radiation. The values of the sensitivity factors obtained showed broad similarities to those employed for low energy sources. Auger parameter studies of metals and alloys require excitation of photoelectrons and Auger electrons from the core atomic levels of the elements of interest, as well as an increased analysis depth since the results are often interpreted in relation to the bulk rather the surface properties of the material. This paper shows that these requirements are met when Cr K β is used as an excitation source. The characterisation of the Cr K β source in terms of achievable resolution and sensitivity is also briefly discussed.