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Angular accuracy and the comparison of two methods for determining the surface normal in a Kratos Axis Ultra X-ray photoelectron spectrometer.

Seah, M P; Spencer, S J (2009) Angular accuracy and the comparison of two methods for determining the surface normal in a Kratos Axis Ultra X-ray photoelectron spectrometer. Surf. Interface Anal., 41 (12-13). pp. 960-965.

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Abstract

An investigation of the calibration of the sample orientation with respect to the spectrometer input lens electron optical axis is reported using two proposed methods: the crystal axis method (CAM) and the overlayer thickness consistency method (OTCM). The study is conducted in a Kratos Axis Ultra X-ray photoelectron spectrometer. First, the emission angle settings of the sample holder are calibrated with respect to the mechanical axis. It is found, using a laser beam system, that there is a significant error in the instrument's sample stage tilt angle calibration which increases with the emission angle with a maximum error of 5°. This is attributed to the use of a low-torque magnetic rotary drive that is increasingly offset by the restoring torque from internal cooling coils. After calibration of the tilt scale, the zero angle of emission with respect to the electron optical axis, using the CAM, is found to be 0.26° ± 0.07°. Using the OTCM, it is found that it is more likely that the consistency should be homogenised around 0° emission rather than over the 10° - 40° range proposed. The exact emission angle for homogenisation is unclear and present calculations of electron transport are insufficiently accurate to define this. The precise way to use the OTCM method is, therefore, unknown. It is recommended that only the CAM be used, that analysts check that the sample stage tilts at a rate of 1° per 1° set by the user over the likely emission angle range to be used, and that manufacturers consider these angles carefully in instrument design.

Item Type: Article
Keywords: Angular accuracy, geometry, quantification, surface normal, XPS, X-ray photoelectron spectroscopy
Subjects: Nanoscience
Nanoscience > Surface and Nanoanalysis
Last Modified: 02 Feb 2018 13:15
URI: http://eprintspublications.npl.co.uk/id/eprint/4522

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