EDX method is only a qualitative method. we can not quantify by EDX method. oxygen, Nitrogen, carbon peak can be obtained by these peaks may be from atmospheric or carbon tape. for hydrogen, EDS cannot detect the lightest elements, typically below the atomic number of Na for detectors equipped with a Be window. Polymer-based thin windows allow for detection of light elements, depending on the instrument and operating conditions.

The reason is very simple. EDX is related to the K-shells which are not the valence shell. H does not have a K shell, or , better to say, it has only a K shell in convalent bonding and this only electron is shared. In energy dispersive SEM you can be reliabele signal from about Na on, in wavelength dispersive SEM you can see the second row elements too.

Hi,

Gyorgy gave the correct answer.

Here is my reply to a previous related question: Why we are unable to detect Hydrogen and Helium by x-rays? (https://www.researchgate.net/post/Why_we_are_unable_to_detect_Hydrogen_and_Helium_by_x-rays)

"There is an excellent paper on this topic by Nenad Stojilovic, Why Can’t We See Hydrogen in X-ray Photoelectron Spectroscopy? J. Chem. Educ., 2012, 89 (10), pp 1331–1332. DOI: 10.1021/ed300057j.

Below is just the last paragraph of this stimulating paper: "Hydrogen has no core electrons and, therefore, core−electron XPS is impossible. The H 1s electrons are valence electrons and as such participate in chemical bonding. Any signal from hydrogen would overlap with signals from excitation of valence electrons from other surface atoms. Namely, photoionization cross sections for valence electrons are also small and their binding energies significantly change with chemical environment. Also, the valence orbitals often appear in the spectra as broad bands. It is generally not possible to distinguish between H 1s valence electrons and valence electrons of other elements. Therefore, H 1s valence electrons are not useful in elemental identification using XPS method."

Hope this helps.

Best,

Yang

Hello Dr. Gyorgy Banhegyi and Dr. Yang Gan,

What could be the reason for not getting reliable data for Boron detection in EDAX, despite the fact that its K shell electron are not valence electron.

Dear Raeesh,

You raised a very good point about problems in EDX analyses of light elements including B. I recommend this nice document which gives explanations and how to overcome the problem. Here is some parts of except from it.

SEM/EDX ANALYSIS OF BORON, by Linda Ingemarsson & Mats Halvarsson of High Temperature Corrosion Centre (HTC), Chalmers University of Technology

Link:http://fy.chalmers.se/~f10mh/Halvarsson/EM_intro_course_files/SEM_EDX%20Boron.pdf

"Why is light element difficult to analyze (with SEM/EDX)?

Analysis of the light elements, i.e. Be, B, C, N, O and F, is difficult because of their low photon energies. Low photon energy leads to many complications such as:

1. a high absorption in the specimen and in the detector

2. the low energy peaks is positioned close to the electronic noise of the detection system (which can be seen at about 0 keV)

3. with light element this gives a low yield of X-rays

When having a higher atomic number element this gives a spectra with more peaks and permits the use of an alternate peak if overlap in spectrum occurs in the specimen.

The high absorption in the detector results in a incorrectly measurement of photons and consequently a shift in the peak position.

Conclusions (of their study):

This study has shown that it is possible to analyze boron by the use of SEM/EDX. The EDX quantification was based on the following principles:

1. optimizing the accelerating voltage so that a strong boron peak, and a high spatial resolution, is achieved

2. check that there is no overlap between peaks of boron and other elements in the EDX  spectrum

3. performing the drift control manually since the sample exhibited charging

The EDX quantification provided a rough estimate of the composition of the boron containing silica and for this study that was an acceptable result. For a more precise value of the composition, a reference material would be required."

Again hope this helps.

Best,

Yang

Dear Prof Yang,

Thank you so much for explanation.

regards

raeesh

However, you can get EELS spectrum of hydrogen (Gatan digital micrograph).

Hi Ayan,

Thanks for your follow-up.

I do not think TEM (or STEM)/EELS has been used routinely for H analysis. It is by no means straightforward; instead, it is a challenging project for each this kind of analysis.

There are indeed reports about EELS study of the metal-hydrogen systems by comparing plasmon shifts without/with H by EELS measurements of valence electron density. But this is a very challenging task. Here is the other example of the controversy about EELS study of H in solids—Laurence A.J. Garvie, Can electron energy-loss spectroscopy (EELS) be used to quantify hydrogen in minerals from the O K edge? Am. Mineral. 95 (2010) 92-97.

In principle, for routine elemental or chemical bonding analysis from Li to U, usually signals from high energy loss region (ΔE > 50 eV) are used (the so-called core-shell EELS). Usually, low energy loss region (ΔE < 50 eV) is used for thickness determination, valence electron density study or dielectric function study (then for refractive index and extinction coefficient determination).

Below is the official notice from the GATAN website for their EELS/EFTEM system (link: http://www.gatan.com/techniques/eelseftem): “Core level EELS is sensitive to all elements in the periodic table (with the exception of atomic hydrogen) but is particularly sensitive to light elements.”

However, in the very low loss energy range where H edge (~10 eV) lies, bulk materials’ plasmon peaks may overlap strongly with H edges if not considering the background noise.

(Note: Gatan DigitalMicrograph, mentioned by Ayan, is not a hardware update or attachment, but one of Gatan’s Microscopy suite software for quick and advanced analysis with built-in scripting language and plug-in applications, like for micrograph analysis as well as EELS/EDS analysis using hydrogenic or H-F models, etc.)

Lastly, of course, it is well established to study gas molecules (like hydrogen) adsorption and solids using special low energy EELS (HR-EELS with excellent energy resolution but no spatial resolution) with ΔE less than 0.5 eV. But, this is completely the other story.

Hope this helps.

Best,

Yang

Limitations of quantitative analysis

Some of the limitations of quantitative EDS analysis are listed below:

Light elements (Z < 11) cannot be routinely analysed by EDS.

Hydrogen (Z = 1) and He (Z = 2) do not have Characteristic X-rays, and the Li (Z = 3) K X-rays are of too low energy to be detected by EDS.

Beryllium (Z = 4) to Ne (Z = 10) X-rays can be detected by EDS, but there are two problems. Firstly, they are low energy X rays subject to strong absorption by the specimen. Secondly, the electrons involved in generating the Characteristic X-rays are also the valence electrons involved in the chemical bonding of the element, therefore the shapes and positions of the peaks may change in different compounds. The samples and the standards must be closely matched for best results.

for further details

http://www.ammrf.org.au/myscope/analysis/eds/quantitative/

Hi Ganapathi, 

This is a very good link—plenty of useful information, even for experienced users. Strongly recommended!!!

Best,

Yang

Gregory, Yang and Ganapathi have already provided a good set of explanations and references to answer the original question posed by B. Neelakantaprasad.

If I may add a consideration on the detection of light elements by EDS (or devices based on a similar principle), the most recent advancements consist of:

- A new SDD-based windowless wide area EDS detector by one of the main manufacturers of these equipments, which has demonstrated the capability of analyzing light elements such as lithium, nitrogen and oxygen as well as the low energy lines of heavier elements, hence providing a new device for use with low voltage operation of FEG-SEM’s.

- A new “Soft X-ray Emission Spectrometer” (SXES) which uses an aberration corrected grating system and a high sensitivity X-ray CCD for the simultaneous collection of a full energy spectrum (within the range of the grating). Conceptually this device is somewhat in between an EDS and a WDS system and it’s claimed to provide a superb sensitivity for light elements (e.g.: a few 10s of ppm B in steel) and an energy resolution of 0.3eV in the energy range 50eV – 210eV. The spectrometer can easily detect Lithium and can provide a chemical state analysis (valence bond) comparable to that of XPS or EELS.

Dear Dr. B. Neelakantaprasad

Regards

Yes, the light elements cannot be easily detected by EDX. Therefore researcher resort to use XPS to identify such elements.

Greeting

Dear Dr.  Yang,  

Is it possible to differentiate residual oxygen present on the carbon tape from the oxidized sample using EDX?

for the preparation of samples, sample is pasted with carbon tape so carbon is present in the sample.

Hi all. Does EDX can detect presence of gas trapped in metal oxide amorphous layer? for instance, Ar gas trapped in Si oxide layer.