SiO2/Si is the substrate used by default in the investigation of two-dimensional materials such as MoS2. I understand the advantages this substrate has such as its flatness, chemical inertness, and the good optical contrast for optical inspection of single layers due to light interference. But I wonder if someone has investigated alternatives to SiO2/Si and why.
Dear G. G. Yao
Is it possible to identify monolayer on mica sheet and Raman study?
Very often we use few layers of 2D h-BN as a substrate on top of SiO2/Si to reduce trap charge (in SiO2) induced carrier scattering in 2D TMD channel. If SiO2 trap charge induced scattering is critical for your 2D TMDs, then the above strategy would be helpful.
@ Chandan Biswas
i used h-BN as dielectric substrate and study FL-ReS2 photo detector characteristics but the results are good in increase in photo responsivity and EQE as compared to SiO2 substrate. But i have seen increase in rise time on h-BN substrate however the decay time for FL-ReS2 is low on h-BN substrate as compared to SiO2 substrate. Please if you have any knowledge or relative paper, recommend me . Thanks
@Ghazanfar Nazir
Fortunately, I checked this post again and just saw your Q. It seems like ur trap charge may be effecting photodetector behavior. However, with this little information in can not comment it for sure.. If the time constant is in ns/ms range then it could be active layer induced trap charge. If its in the order of sec then may be substrate induced trap charge. Photogenerated trap charge in the active layer (different from substrate induced trap charge) also can effect as well as photogenerated trap charge in the substrate. Photogatting effect also you can see. So there are many factors here and u need to find more appropriate info accordingly.. I dont know if it will help, I had a NanoLetter paper Article Negative and Positive Persistent Photoconductance in Graphene
: talking about trap charge induced photoconductivity in Graphene. Check if you get any info from there. Also dont rely solely on my comments, I have very little info to think, but may be give u some direction.. Good luck..
Dear Raul D. Rodriguez and the other followers,
From the optical point of view, also Si3N4 is a good candidate if deposited by LPCVD. We observed a very high contrast at least for graphene to make it clearly visible. Furthermore, we also calculated the contrast for other 2D materials and considered Al2O3, too, in the calculation and were able to count graphene layers with a very simple measurement equipment. You can read our papers regarding this things:
dx.doi.org/10.1063/1.4973968
dx.doi.org/10.1021/acs.jpcc.9b00957
I hope it is helpful. However, we did not study the influence of electrical properties of the dielectrics including interface defect states etc., yet.
Best regards
Christian
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