Gayatri, although you have mentioned that you're essentially interested in the structural characterization (btw.: atom probe microscopy mentioned above might really be interesting in this respect - do check it out!), I would also go for the consequences of low-dimensionality.

You did not spell out (or I overlooked it) just how low-dimensional your system is. In principle it could be as little as a single dichalcogenide sandwich layer. In the bulk, these systems have little but finite band dispersion along the direction perpendicular to the layers. Also, in case of AB-type sandwich stacking (2H-polytype) the non-symmorphicity of the corresponding space group imposes specific symmetry properties onto the electronic states. (A single layer would rather correspond to a quantum well system with standing waves along the surface normal and hence no dispersion, ideally.)

These things can very well be observed with photoelectron spectroscopy, though not XPS (mentined above) but ARPES (VUV photon energies). For the band dispersion and symmetry properties perpendicular to the layers, angular variation is not required (angular resolution is, though) but variable photon energy is a must and thus synchrotron radiation is required. Of course, your specimens must somehow conform to the requirements of this highly surface sensitive technique which is performed in ultrahigh vacuum. If you are interested, the following article might be a starter: http://prb.aps.org/abstract/PRB/v55/i16/p10400_1 .

Well, XRD and XRR come to mind. Is that what you want to do? I've got difficulties to imagine from your question what exactly it is you want to know.

You dont have mentioned what type of layered structure you want to characterize. However XRR can be used with another complementary technique scanning probe microscopy.

Thank you Dieter. I have nanopowder of bismuth chalcogenide and I want to find out if it shows layered structure similar to bulk material.

I also work with layered structures, but mainly Clay materials. If you have small degree of layered structure, XRD patters should show the same d-spacing as bulk; but, it could be less in intensity

To identify the layered structure you may use XRD, XRR and SEM!

EDS technique may be useful as well to obtain a composititon profile and location of the different layers.

Thanks everyone!

If you want to characterize atomically layered structure, you need local probe techniques such as TEM or STM. SEM is good only for a limited range of resolution. EDS can probe individual layers only if they are wide around 1 micron otherwise you will have overlap across the beam-specimen interaction volume

In order to characterize materials of atomic layered structure, one can use X-ray scattering or diffraction techniques such as, for examples, XPS, TEM, SEM or EDX, XRD. with this technique one can study layers structure as well as materials chemical composition. Also you can use techniques such as LT STM or LT STM in AFM mode. Raman spectroscopy is also very useful in this context.

I think that SEM is a good technique in order to compare different layers structures. TEM is able to determinate what phases are present in each layer.

I am biased towards electron microscopy (since there is so much "direct" characterization that you can perform in your samples, often within the same instrument, and in the same session). However you did ask for methods other than EM… A fair question to ask is "What properties do you want to characterize?"

If you're interesred in the layer spacings, I'd first go with XRD for your powders. You can get info regarding the average sizes wihin your sample. (Then you'd have to sort out what measurements correspond to which spacings… )

Hi

The principle techniques are [*] Induced X-ray emission spectroscopy (IXES) and [**] backscattering (BS). Under IXES there are the techniques of PIXE and SEM. These are based on the same principle. (The P in PIXE is for ant particle, but normally proton are used). As said in PIXE the particles are proton and in SEM they are electrons. The principle is: the specimen is bombarded with the energetic particle (~3MeV). The electron in the atom is excited to a higher state. The bombardment is stopped (time equivalent of milli seconds). The electron returns to the previous state. X-ray energy is given off. This X-ray energy is specific to the atom. (The beauty is that) even if the atom is in a specimen such as industrial product or biological products, the x-rays of the atom that are emitted, are given of at the very same energy (measured in keV). That is, IXES is standardless. (Protons and electrons, so what's the differences.) there are a few of them.

[+] The detector for PIXE is sensitive. Backscattered particles can damaged it. So the window of the detector is thick (in the sense of micrometers).this means that the X-rays of light elements eg. C, N etc are absorbed in the window of the detector and do not reach the measuring parts. These elements cannot be detected with PIXE but with SEM.

[++] very important!!. The minimum amount that can be detected, minimum detection limit (MDL). A proton is ~2000 times the electron-do not bother in what, just 2000 times. Imagine the two collide! The effect of the electron is virtually nothing. (If the electron could shout, no-one would hear it in the background. More so, what if the speed of the proton increases, virtually zilts.) but is two electrons collide, the background noise would be orders of magnitude greater.

(So what's the moral of the story so far?)

With SEM I can analyze light elements, but not with PIXE, but for SEM MDL is 0.065% -my experience- for PIXE it is 0.00005% or 0.5 ppm. (Remember 100% = 1000000 ppm; 1% = 10000 ppm).

(Wow, let's continue).

Now for the layers in the structure. If the layers are micrometers thick then BS is the right one. (Oh yes, PIXE and BS CAN BE DONE AT THE SAME TIME.) as the proton penetrate through the layers it looses energy; oh and then all the equations. In the end you get the thickness and the element in the layer. MDL for BS not less than 1%. If the layers are thicker, cut a cross section, turn it on the side nd then do these analyses.

REMEMBER YOU CAN DO MAPPING WITH THESE TECHNIQUES, AND THE SOFTWARE ARE AVAILABLE. Most of all these techniques are non-destructive. You can analyze samples over and over and... Again.

And that is it; a layman's introduction. I did this for bth my specializing first year and masters and PhD students. I hope this helps. Let me know where you are since there will be facilities nearby.

I am interested in atomic structural characterization to study atomic layered structure and different stacking sequences between atomic layers and phase analysis. I do not have an access to XPS, STM, I will use other X-ray absorption and diffraction techniques. Johan, I am in the northeast part of USA.

I think XPS will be the best to characterize it specially using depth profiling !!!

The following reference may be helpful: John C. Vickerman (Ed.), Surface Analysis -- The Principal Techniques, 1st ed., John Wiley & Sons, Chichester (etc.), 1997; John C. Vickerman, Ian S. Gilmore (Eds.), Surface Analysis -- The Principal Techniques, 2nd ed., John Wiley & Sons, Chichester (etc.), 2009. Cf. http://www.wiley-vch.de/publish/en/books/bySubjectMS00/bySubSubjectMS80/0-470-01763-5/?sID=zemyeh5lb

Characterization technique of semiconductor materials with layered structure is the same as for bulk crystals of cubic (or other) symmetry. However, in the case of low-dimensional systems the appearence of the quantum-size effect (when size of nanoparticle is comparable with Bohr radius of exciton) is possible. This effect strongly affect on the energy structure of such systems. In particular, increase of band gap occurs. Effective methods of the study these changes are optical measurements (absorption and photoluminescence spectra). This also allows to determine the sizes of nanocrystallites and their size distribution. Then, these results can be comparated with data of the structural measurements. As an example of such complex studies for the layered nanoclusters may be found in work which attached.

TEM if you want to have a local idea, XRD if you want to have a more realistic information on your specimen.

However, HUGE warning: this is far from being easy. Layered materials (especially those that have some industrial application or enhanced properties) show stacking disorder and therefore the traditional analysis tools (based on a 3D periodic lattice) don't always work (I am currently working mainly on the analysis of layered materials using XRD). I can give you a reference:

https://www.researchgate.net/publication/230824183_Simultaneous_refinement_of_structure_and_microstructure_of_layered_materials

and I can provide the software if interested.. The software comes with a simulated example of an hypothetical powder made of a partly disordered ZnS-CuS interlayered structure

Article Simultaneous refinement of structure and microstructure of l...

Gayatri, although you have mentioned that you're essentially interested in the structural characterization (btw.: atom probe microscopy mentioned above might really be interesting in this respect - do check it out!), I would also go for the consequences of low-dimensionality.

You did not spell out (or I overlooked it) just how low-dimensional your system is. In principle it could be as little as a single dichalcogenide sandwich layer. In the bulk, these systems have little but finite band dispersion along the direction perpendicular to the layers. Also, in case of AB-type sandwich stacking (2H-polytype) the non-symmorphicity of the corresponding space group imposes specific symmetry properties onto the electronic states. (A single layer would rather correspond to a quantum well system with standing waves along the surface normal and hence no dispersion, ideally.)

These things can very well be observed with photoelectron spectroscopy, though not XPS (mentined above) but ARPES (VUV photon energies). For the band dispersion and symmetry properties perpendicular to the layers, angular variation is not required (angular resolution is, though) but variable photon energy is a must and thus synchrotron radiation is required. Of course, your specimens must somehow conform to the requirements of this highly surface sensitive technique which is performed in ultrahigh vacuum. If you are interested, the following article might be a starter: http://prb.aps.org/abstract/PRB/v55/i16/p10400_1 .

If you to have an idea about the ability of XPS to study layered structures, you may read the following reference: M. Raposo, J.M.C. Lourenço, A.M. Botelho do Rego, A.M. Ferraria, P.A. Ribeiro, Colloids and Surface A: Physicochemistry and Engineering Aspects 412, 1-10 (2012). (DOI:10.1016/j.colsurfa.2012.05.005).

I see I had previously missed the point that you have a powder. To do what I described above would require working on a single flake. Not impossible, maybe, in a suited PEEM instrument (photoelectron microscope of the kind allowing to measure photoelectron spectra with sufficient energy resolution), but definitely a challenge!!

I see you guys are discussing about characterizing samples that has not been described fully. One must know what that is. Is it a powder sample or thin film? Is it epitexial? If it is powder and of sufficient amount then X-ray and/or neutron diffraction are suitable techniques. If the system is inherently layered like for example, GeS, GeSe, SnS and SnSe (narrow band gap IV-VI semiconductors, then diffraction should be the proper technique. These structures do not change much even in thin film forms or in nanoparticle form, I guess. Gayatri, please describe your sample more precisely and then you get proper answers.

Thank you Tapan for your suggestion. As mentioned before, my samples are nanostructured powders. I have enough sample to run XRD.

You should then try first X-ray diffraction. Of course the diffraction peaks would be wider than the resolution of the instrument but that all depends on the particle size. Do you already know the average particle size? If the bulk structure is known then you can try to do Rietveld analysis by assuming the bulk structure remains more or less the same in your nanosamples. Once you have a reasonable fit with the model then you know hat the bulk structure is approximately right but the surface of the nanoparticles may have relaxed atomic coordinates. You may have different stacking of layers close to the surface. If you wish to go beyond this then you have to do PDF analysis and some modeling. I guess all these will be necessary if your particles have size less than about 10 nm. In this case you have to have good X-ray or neutron diffraction data up to a very high Q (two-theta) and the backgrounds (empty sample holder and sample environment) should be carefully measured. You must do some modeling of the nanoparticles and by fitting your model with the PDF data you can get the real structure of nanoparticles. This will be a hard job but you will be certainly rewarded for this work. Another approach is to try measure X-ray diffraction from a single nanoparticle at a synchrotron source like APS or ESRF in a microfocus beamline. But this is a hard job and so far one can measure do down to about 30 nm size at the ESRF on the ID11 beamline.

Gayatri! Hi! I guess I'm new to RG hence I've been missing out on all these juicy topics. I see the familiar cast of characters (experts) among the contributors and couldn't help jump in. Once again thanks for sharing all your intense thoughts freely. I haven't read all your comments yet. I will and then post my remarks.

If you think that your material can present some chemical gradients related to the layered strcutures; I recommand you to test GD-OES to reveal them. Some precautions have to be considered: perfect polish section parallell to the gradient and layered strcutures; conductive samples if not special conductive thin film can be recommanded; used pulse signal with GD and ablation rate have important and in few seconds you can get data so take care during test. To my point of view this is one of the fast accurate method for structural material with potential chemical gradient

I can add to the comment of Philippe Coustumer that GDOES is capable to detect most of the elements of the Periodic Table starting from hydrogen, with resolution as high as 1-2 nm if specimen is prepared properly. Further, it can also detect selected polyatomic species, e.g. OH groups, if configured properly. Related to the duration of the analysis, for example, anodic film on aluminium of 300-400 nm thickness is typically analysed for 20-30 s.

What range of periodicity are you interested in measuring Gayatri?

XRD would allow you to evaluate diffracting domain sizes from 10's of nm to 100's of nm depending on the technique used. NDE WAXS or SAXS. It would be easier for us to suggest the probable approach once we understand the dimensions involved. Please indicate the "domain sizes" that you are interested in evaluating. My expertise with the chemistry and Nano structure of the typical materials you are working with is limited. If you have some typical SEM or TEM micrographs of similar materials, that would be helpful. As Tapan mentioned, a better description of your sample would go a long way. Do you expect any presence of preferred orientation?

Glow-discharge optical emission spectroscopy (GD-OES)

X-ray photoelectron spectroscopy (XPS)

X-ray Powder Diffraction (XRD)

Just to document / keep it as record in this thread:

as for many other Q/A-threads, RG's statistics also for this Q/A aren't correct either :

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