The high carbon and oxygen intensity is probably due to surface contamination. As a starting point, look at the ratios of the elements of interest.

EDX is generally good for confirmation and identification of elements. It gives approximate estimation of the ratio of elements present in the materials. Oxidation and surface contamination should be avoided for good quantification.

You have very good EM facilities at your university and I believe you can discuss your results with an operator face to face, in detail. For sure results you were given are not good, not up to the level I would expect for your EM lab. For beginning I would ask these questions:

- Why C content was so high? Was specimen coated with C (but who need it for a metallic specimen?) or SEM is just very dirty, with high level of carbon contamination?

- Where O and F came from? Wrong identification?

- Why quantification was performed without utilization of standards (standardless quantification is prone to errors)?

- In how many spots analysis was performed (test for homogeneity and/or presence of a second phase)?

For beginning you can discard results for C and O and normalize the rest of elements. It will give you some insight, but results will be still poor. For example you have too high concentration of S, possibly because its peak was superimposed with Nb L peaks.

For sure, a C and O contamination in you SM chamber. I had this problem in mine 15 years ago ans now I do regular clean-up of the detector's window and calibration checks on my system. Contact the maintenance service of the manufacturer could help you to properly answer this question...