Assuming that the lanthanum is distributed evenly throughout the depth of the film.
Since La3d and La3p are both lines with rather high cross sections, it sounds counterintuitive that they are not seen.
How certain are you regarding the distribution homogeneity?
How thick is the film you are analyzing
By drawing a comparison between the EDX and XPS analyses, It is crystal clear that the XPS data has a more acceptibility than the EDX data. Indeed, the EDX has so many errors and it often show some element which does not exist in your samples. While, the XPS analysis provides a convincing and reliable results.
@Jürgen Weippert thickness is about 800 nm. EDX shows good homogeneity. ??!!
OK, the depth of XPS is in the 1-10nm range, so your film definitely has a thickness at which results may differ.
Do you have access to an XPS which allows for (admittedly destructive) depth profiling? Then you could exclude or verify homogeneity as the reason.
If the lanthanum is distributed evenly throughout the depth of the film, it is still possible that the element is not detected by XPS. In this case, the limitation of XPS detection depth could still play a role. Since XPS can only probe the surface layers of a sample, it may not be able to detect the lanthanum that is buried deeper within the film.
Additionally, the concentration of the lanthanum in the thin film could be below the XPS detection limit. XPS is a technique that requires a certain minimum concentration of the element of interest to produce a detectable signal. If the concentration of lanthanum is too low, the XPS measurement may not be sensitive enough to detect it.
It is also possible that the lanthanum is present in a chemical state that is not detectable by XPS. The chemical state of an element can affect the binding energy of its electrons, which in turn can affect the signal produced by XPS. If the lanthanum is present in a chemical state that produces a weak or no signal in XPS, it may not be detected even if it is present in the film.
Overall, XPS and EDX are complementary techniques, and it is always recommended to use multiple analytical methods to confirm the composition and structure of the sample.
If the thickness of the film is about 800 nm and the lanthanum is distributed evenly throughout the depth of the film, it is less likely that the limited detection depth of XPS is the cause of the issue. However, it is still possible that the lanthanum concentration in the film is too low to be detected by XPS, or that the lanthanum is in a chemical state that does not produce a detectable signal in XPS.
Another possibility is that there could be an issue with the XPS measurement itself. For example, there could be sample charging or contamination that is affecting the XPS signal. It is important to carefully prepare the sample for XPS measurement to ensure reliable results.
If the EDX analysis shows good homogeneity of the lanthanum in the sample, it suggests that the lanthanum is present in a detectable concentration and that the XPS measurement conditions should be optimized to improve the detection of lanthanum. You could try adjusting the XPS instrument parameters, such as the excitation energy, measurement angle, or detector sensitivity, to see if this improves the detection of lanthanum in the XPS spectra. Additionally, it is always recommended to use multiple analytical methods, such as XRD, TEM, or SIMS, to confirm the composition and structure of the sample.
Jürgen Weippert yes the only possibility is the inhomogeneous distribution of La along the thickness of the film. so I am going to investigate the depth profile of the film. But with the contamination with Carbon reduce the peak's intensity???
Khaled Abdelkarem
hi Kkahed , I hope you are ok in the USA
regarding your suggestion about the detection limit, what EDX can detect, XPS must detect, and more. So the detection limit is not the issue of this undetectable La.
the same machine can detect La-into Co3O4 and other compounds so I think it will already calibrate.
anyhow thanks for trying to help with this issue.
Ahmed A. Aboud
Hi Dr. Ahmed, I'm doing well, thank you.
If the same XPS instrument can detect lanthanum in other compounds, then it is likely that the issue is not with the instrument's calibration or sensitivity. In this case, it could be that the lanthanum in your thin-film sample is in a chemical state that is not detectable by XPS, or that there is an issue with the sample preparation or measurement conditions that is affecting the XPS signal.
XPS is a technique that is sensitive to the chemical state of the elements in the sample. The binding energy of the electrons in an element can vary depending on its chemical environment, and this can affect the XPS signal. Therefore, it is possible that the lanthanum in your thin-film sample is present in a chemical state that is not detectable by XPS.
Another possibility is that there is an issue with the sample preparation or measurement conditions that is affecting the XPS signal. For example, sample charging or contamination could be affecting the XPS signal, or the XPS measurement conditions could be suboptimal for detecting the lanthanum in your sample.
It is also worth noting that EDX and XPS are complementary techniques with different detection limits and sensitivities. While EDX can probe a larger volume of the sample and has a higher detection limit, XPS is more surface-sensitive and can provide more detailed information about the chemical environment of the elements in the sample. Therefore, it is possible for EDX to detect an element that is not detected by XPS, or vice versa.
Overall, it is recommended to carefully review the sample preparation and XPS measurement conditions, and to consider using complementary analytical techniques to confirm the composition and structure of the sample.
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