I always think that the substrate has enormous effect on the graphene.
It is not difficult to imagine because the vast area of graphene have contacted with substrate, and the substrate has long been considered as major source of charge impurities. (though no one knows where they came from)The clues can be found from the previous work done by Andrei group in Rutgers, they reported that they could approach ballistic transport by suspending the graphene and measured the highest mobility ever in low-temperature about 200,000 cm2/ Vs.
http://www.nature.com/nnano/journal/v3/n8/full/nnano.2008.199.html
And the work related to Raman Spectroscopy
http://pubs.acs.org/doi/abs/10.1021/nn900130g
And the work that focus on the doping effect of the substrate
http://prb.aps.org/abstract/PRB/v79/i11/e115402
Since the previous work I focused is the surface modification of silica surface.
One of the various kinds modification I did is that I capped the silanol groups with HMDS which make silica to be hydrophobic.
And I analyzed the sensing signal change when I injected the buffer with stepwise concentration.
I found that the influence of surface silanol groups is quite important, since they are greatly responsible for the surface potential change in SiNW-FET biosensor. Moreover, I think the ionic behavior is quite different when we replaced the surface groups or capped them.
So, a question has now appeared--
If the so called "charge impurity" mainly came from the ions or ion-like molecules that associated with substrate, what would happen if I capped the surface silanol groups of SiO2 substrate with trimethylsilane?
I think it would be better, at least the mobility should increase, since the ion-like charge impurities would reduce the amount of them which associated with silica prior to the graphene attaching.
