Quick Overview #
overlayer film and substrate are different (for example Rh on a Si substrate) [1].
- Any uniform surface contamination is not important (i.e. advantageous carbon can be
neglected) - Instrumental factors (which may be unknown), would be common to overlayer and
substrate and so cancel out - Works over a range of film thicknesses, from small to large
- Applicable to a wide range of kinetic energies above ca.500 eV
- Simple equation and graphical method with error of ±10% based on accuracy of
attenuation lengths obtained by calculation
The Cumpson-Lee Thickogram by DaveXPS #
HarwellXPS technical director, Dr. David Morgan, has developed an open source modeller for the graphical ‘Thickogram‘ method, developed by Peter Cumpson. Gwilherm Kerherve has incorporated this into KherveFitting, including it as part of the suite of tools in this free and open source software.
Using the Thickogram #
The thickogram can be used by input, or peak selection. Binding energy and intensity (area) can be obtained from your peak fitting models, in the peak fitting parameters section.
In this case, we are looking at a silicon dioxide overlayer on a silicon wafer, and so our RSF is the same for both systems – we can just put this as one.
We have found our IMFP (λ) from TPP-2M already, so we can input that, and hit calculate – and the thickogram plotter will give our overlayer thickness!!
Using the Thickogram #
To use the automatic peak selection tool, first, right click on your peak models and export them to the results section. Then, when you are in the thickogram menu you can brings those peaks in directly, without inputting any numbers yourself.
Here we just use the 2p3/2 peaks, since the ratio between them will be the same as the sum of the entire doublet.
References #
1
Cumpson, Peter J. “The Thickogram: a method for easy film thickness measurement in XPS.” Surface and Interface Analysis: An International Journal devoted to the development and application of techniques for the analysis of surfaces, interfaces and thin films 29.6 (2000): 403-406.
