which technique is suitable to know the elemental composition in a 30-50nm thin film?
I heard that WDX (wavelength dispersive X-ray) could be used.
Is it good technique for this purpose?
please someone share your experiences.
Thank you
XPS is good. Not sure about WDX/EDX, but I think it will also work. I have typically used EDS attachements in tandem with SEM and I believe it is a decent surface analysis technique. You might also want to try looking into Auger electron spectroscopy.
I would also be careful when it comes to your substrates. Some are conductive or could be damaged by electron bombardment, so take care.
Actually it depends on what you need to know. You can use also EDX for the elemental analysis and chemical characterization. This technique gives you procentage estimation of compounds (mass or volume fraction). Accuracy depends on the measurements, calibration samples and other factors. But it helps you to understand what the sample is. If you whant to know elemental and atomic structure only of the thin solid film, TEM will help you. But it is not so easy as EDX and WDX and defenitely not cheap procedure.
I assume that you mean WDX performed in an SEM. WDX is great if you need good energetic resolution, i.e. in cases where the elements you're interested in have overlapping peaks. Otherwise, I'd suggest using EDS (a.k.a EDX, EDAX) which gives similar information but is much more convenient (and faster) to use (and it's also considerably more common to find).
30-50 nm is tricky though, and if you want to use SEM the signal depth/onion for x-rays would be in the order of 100s of nm for typical conditions. The big question becomes: does the substrate also contain the elements that you are trying to quantify? If not, you could try using EDS/WDX in the SEM; the majority of the signal would come from the substrate but you might get enough from the film. You could improve your signal by tilting the sample, and by lowering the interaction volume by lowering the beam energy - but you'll need to make sure that the electrons have enough energy to excite the transitions that you're looking for. If the substrate contains the elements of the films that you wish to quantify (e.g. 50nm Al2O3 over quartz), I wouldn't use SEM for that because you'd have a hard time convincing yourself that no signal is coming from the substrate.
Alternative methods to consider: RBS - should be quite accurate if employed and analyzed correctly (typically done in service labs, $500~1000 /sample).
Last, electron spectroscopies with depth profiling such as AES and XPS might work as well, but you risk possible artifacts caused by sputtering (preferential sputtering, reduction et al.). These can be worked out, but might take some tweaking (and expertise) to verify.
Dear Vikas Singh
Have a nice day and good times
To know the elemental composition of your thin films you can use energy dispersive analysis of X-ray (EDS or EDAX). This technique gives you the percentage of the element in the composition of your thin film sample. You can also use X-ray photoluminescence spectroscopy technique (XPS), It is good one and has high accuracy to appoint the proportion of the elements in your film sample. But using the wavelength dispersive X-ray (WDX) is used to get the energetic resolution of samples.
Good luck
Yours,
Ahmed Saeed Hassanien
Dear Vikas Singh
Have a nice day and good times
I used EDS technique many times to check up the elemental composition of my thin-film samples.
In the appended papers I used this technique. They may help you.
Good luck
https://www.researchgate.net/publication/281495242_Influence_of_composition_on_optical_and_dispersion_parameters_of_thermally_evaporated_non-crystalline_Cd50_S50-xSex_thin_films
https://www.researchgate.net/publication/277004252_Microstructure_and_crystal_imperfections_of_nanosized_CdS_x_Se_1-x_thermally_evaporated_thin_films?ev=prf_pub
Article Influence of composition on optical and dispersion parameter...
Article Microstructure and crystal imperfections of nanosized CdS x ...
Elemental composition and exact ionic state of each elements in the sample can be evaluated using X-ray photoluminescence spectroscopy (XPS).
Insulating samples may get charged during measurement, but that affects mostly the resolution and imaging parts of the SEM operation. If the beam's energy was too high you might be getting x-ray signal from many 100s of nm of the sample, making the signal of the film of interest negligible. What beam energy did you use?
Vikas, I believe that this voltage is way too high for your purpose. Look up the formula, the escape depth of x-rays from the specimen are proportional to ~E1.7 if I recall correctly. I believe that for 20kV you're getting signal from quite a few hundreds of nm, making the signal from the film insignificant.
For thin films, I would recomment grazing incidence XRF as you can control the penetration depth. If you carefully deconvolute your XRF data, then you may get the depth profile of all the elements you are interested in it. Also EDX only provides elemental information unlike the additional chemical informationyou will get by XPS analysis.
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology
- Nanostructures
- Thin Films