  Using a solid electrolyte to tune the carrier density in thin-film materials
is an emerging technique that has potential applications in both basic and
applied research. Until now, only materials containing small ions, such as
protons and lithium ions, have been used to demonstrate the gating effect.
Here, we report the study of a lab-synthesised sodium-ion-based solid
electrolyte, which shows a much stronger capability to tune the carrier density
in graphene than previously reported lithium-ion-based solid electrolyte. Our
findings may stimulate the search for solid electrolytes better suited for
gating applications, taking benefit of many existing materials developed for
battery research.
