Influence of ESCA analyser acceptance angle on measured thickness of thin oxide layers

A theoretical model that takes the influence of the photoelectron take-off angle and the acceptance angle of the ESCA analyser on the photoelectron intensity into account is outlined. From a known oxide thickness, theoretical oxide and metal intensities are estimated for take-off angles ranging from 10° to 90°. The model shows good agreement with experimental values recorded from thin aluminium oxide layers of thickness 15 and 23 A. The model further shows that the oxide thickness estimated from the intensities is lower than the nominal value for the smallest take-off angles. This behaviour is more pronounced for the larger acceptance angles and is confirmed by experimental results. To compensate for the influence of the acceptance angle on the calculated oxide thickness, an experimentally determined effective take-off angle must be introduced at the lowest take-off angles. The ESCA spectrometer used was a PHI 5500 with acceptance angles of ±2°, ±5° and ±7°. Copyright © 2002 John Wiley & Sons, Ltd.