Ultraviolet photoelectron spectroscopy (UPS) and Kelvin probe both yield the surface work-function of a sample.
Suppose the following conditions:
- The Kelvin probe and UPS are in the same environment of ultra-high vacuum;
- They are measuring the same sample with a homogeneous surface property.
Could the work-function values obtained from UPS and Kelvin probe be different? If so, what may have caused the difference?
Both methods are used to measure the workfunction of a material. Theoretically speaking both methods will give the same value, most probable value, but they may differ in the expected errors or the standard deviation of the measuring error.
The Kelvin probe may give more accurate results as it is a zero detection method
where one makes the current in the circuit eqaul to zero at the state of full compensation of the workfunction. But the kelvin can not work for all materials where the UPS may be applicable for all materials.
Best wishes
Dear Zhanhao,
the Kelvin probe gives the work function difference. You need a well calibrated reference sample. The UPS-method allows absolute measurements. I attach 2 tutorials.
With regard
R. Mitdank
Sir, can you please let me know that for which material KPFM does not work ??
Dear Pinki,
For your question, I would say Kelvin probe works for most materials, including those that are proper to be measured by UPS and those aren’t proper due to e.g. low conductivity. The underline here is how to interpret the result. For example, if your kelvin probe is installed in ambient air, there will be surface adsorption or oxidation on your sample which could be removed if using UPS ( e.g. metals). On the other hand though, the sample surface could be damaged if the material is sensitive to high energy UV under the UPS (e.g. the halide perovskites).
So I would say there is no easy answer to this question. One can only refer to the literatures or do trial and error through comparison experiment if there is no references. The effort itself though is not a waste of time, it may turn into a small publication of your bigger study.
Hope it helps.
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