Is it possible to characterize monolayer WSe2 or MoS2 by XRD? XRD is a good way to check the crystal structure of the material, but I am not sure whether it is suitable for the sample which is very thin (only 1 layer).
Yanan,
If you mean one mono atomic layer, the answer about XRD application is "no".
What is the best method for you, one can say if you specify what kind of characterization you need.
Regards.
Low beam energy SEM or TEM might be useful. Both can give you X-ray analysis as well as Auger (SEM). However, the sample might need special handling to prevent beam damage.
I hope it helps.
What do you mean when you say "only 1 Layer". If it is 1 atomic layer, as said Yuriy, the answer is no even you use the grazing angle.
No! The penetration depth of x-rays at XRD energies corresponding to a few Angstrom to get a diffraction pattern is is a few hundred monolayer. I f you put it on a single crystal substrate and deposit on top and you get some order LEED might help you. If you just want to measure composition and chemical states you can try XPS preferrable with synchrotron radiation so you can optimise probing depths and cross sections. It must surely be something in the literature on this. MoS2 has been a lubricant for avery long time-
Actually, the best way to analyze the structure of very thin materials is Grazing Incidence Fast Atom Diffraction (GIFAD). This is a new technique that we have developed; it so surface sensitive that it only sees the last atomic plane. In fact it probes the surface electron density just as an AFM does, but in the reciprocal space. We recently measured the structure of monolayer Graphene on SiC by determining both the electronic corrugation of (pristine) graphene and the Moiré-like geometric corrugation (see attached publications)...
there are many studies for TMDCs (Transition metal dichalcogenides). but to growing is hardship because of while bulk TMDC is indirect bangap, monolayer TMDC have direct bandgap. and monolayer TMDC have weak Van der Waals forces hold the sandwich
together resulting in interlamellar mechanical weakness. so, before metarial characterization is determination, you should determination suitable growing conditions. I sure that also XRD characterization technique is useful when TMDCs are generated under the suitable growin conditions.
have a nice working..
Yanan,
Raman is useful for characterizing monolayer. If you want to characterize MoS2 use raman for monolayer at 100X. You will get sharp E1g and A2g peak blue and red shifted accordingly. Grazing angle is difficult for monolayer but long time(4 to 5 hrs) exposure from 8 to 15o (2thetha) can help. Recently I tried and got a faint peak of MoS2 within 13.5 to 14. Hope it helps.
In my Lab, we use Raman, and sometimes MEV, i'm trying to use XRD in some cases, when I do not know if I have cystal MoS2 or monolayer MoS2, but with no success yet
I wonder that some researchers think about XRD for one atomic thick 2D-like shape materials. Of course it is impossible, because The XRD idea depends on Bragg's diffraction law which indicated that to get diffraction you need at least two layers to verify Bragg's diffraction law.
To be sensitive to the in plane crystallography you need to use XRD at grazing incidence, this is called GIXRD. In this case, you can be sensitive to one monolayer. But this technique require a high flux (total reflection condition), so it is often performed at synchrotron radiation facilities.
Dear Yanen,
I think XRD has some limitations for peak observation for WSe2. For peak observation, Raman spectroscopy to characterize monolayer may be advisable.
Refer this site:
https://www.researchgate.net/publication/321821897_In-Plane_X-ray_Diffraction_for_Characterization_of_Monolayer_and_Few-Layer_Transition_Metal_Dichalcogenides_Films
Ashish
- Badges
- Science topic