Inderjeet - yes of course. There are several reasons for such a "misinterpretation":

First of all it could be that you dopant accumulates / segregates at the surface, so the results are not wrong but physically sound.

Second, XPS analysis relies on homogeneity of your sample. If you have a layered, inhomogeneous distribution of the elements within the sample, you clearly need to have an appropriate model that accounts for such deviations - otherwise the output of an XPS quantification is wrong.

You may check if your sample is homogeneous or not by angle-resolved measurements, i.e. by a variation of the exit angle of your photoelectrons and measuring the intensity ratios of the relevant elements! Check the literature on this, I can recommend the publications by Peter Cumpson in J. Electron Spectr. Related Phenom 73 (1995) 25 (DOI: 10.1016/0368-2048(94)02270-4, https://www.researchgate.net/publication/223785855_Angle-resolved_XPS_and_AES_Depth-resolution_Limits_and_a_General_Comparison_of_Properties_of_Depth-profile_Reconstruction_Methods) - although this article is already more than 20 years old, I personally feel that it contains the most important features to be considered for XPS data analysis!

good luck, Dirk

Article Angle-resolved XPS and AES: Depth-resolution Limits and a Ge...

Inderjeet - yes of course. There are several reasons for such a "misinterpretation":

First of all it could be that you dopant accumulates / segregates at the surface, so the results are not wrong but physically sound.

Second, XPS analysis relies on homogeneity of your sample. If you have a layered, inhomogeneous distribution of the elements within the sample, you clearly need to have an appropriate model that accounts for such deviations - otherwise the output of an XPS quantification is wrong.

You may check if your sample is homogeneous or not by angle-resolved measurements, i.e. by a variation of the exit angle of your photoelectrons and measuring the intensity ratios of the relevant elements! Check the literature on this, I can recommend the publications by Peter Cumpson in J. Electron Spectr. Related Phenom 73 (1995) 25 (DOI: 10.1016/0368-2048(94)02270-4, https://www.researchgate.net/publication/223785855_Angle-resolved_XPS_and_AES_Depth-resolution_Limits_and_a_General_Comparison_of_Properties_of_Depth-profile_Reconstruction_Methods) - although this article is already more than 20 years old, I personally feel that it contains the most important features to be considered for XPS data analysis!

good luck, Dirk

Article Angle-resolved XPS and AES: Depth-resolution Limits and a Ge...

I would also question the homogeneity of your sample. You can try angle resolved measurements and measurements at different spots across your sample, also sample to sample variability to get an idea about how homogeneous the samples are.

XPS analysis relies on homogeneity of your sample so analyse at different spot across your sample..

The previous comments are correct. But I would phrase it differently: XPS is a surface sensitive technique. So you only measure the concentration of your dopant in the top few unit cells (if the material is crystalline). Angle resolved XPS would indeed give you ideas of the accumulation of the dopant towards the surface, but you would still not get bulk dopant concentrations...

I think there are two ways of getting better and more detailed information on the distribution of your dopant through your sample:

(1) cutting and polishing your sample so you get a cross section of your oxide material. But this depends on the size of your sample and there's a large possibility of contaminating your sample during the whole process.

(2) using Arong ion etching to get a depth profile of your sample.

Argon etching (sputter depth profiling) might however also suffer from preferrential sputtering (especially if the masses of the elements of interest are very different), and thus an influence on the determined elemental contributions if also afflicted with some uncertainties.