Abstract
We present experimental studies of both local and macroscopic electrical effects in uniform single- (1LG) and bi-layer graphene (2LG) devices as well as in devices with non-uniform graphene coverage, under ambient conditions. DC transport measurements on sub-micron scale Hall bar devices were used to show a linear rise in carrier density with increasing amounts of 2LG coverage. Electrical scanning gate microscopy was used to locally top gate uniform and non-uniform devices in order to observe the effect of local electrical gating. We experimentally show a significant level of electric field screening by 2LG. We demonstrate that SGM technique is an extremely useful research tool for studies of local screening effects, which provides a complementary view on phenomena that are usually considered only within a macroscopic experimental scheme.
Highlights
Graphene has received much attention in recent years due to its unique electronic properties
As EF for 1LG and 2LG are aligned, the position of the Dirac point (ED) is shifted down for 2LG (Figure 5A top inset). This increases the density of states (DOS) in the 2LG system, which is observed as an increase in the carrier density with bulk transport measurements (Figure 5A)
In summary, we investigated the effects of electrical screening in uniform and non-uniform 1-2LG graphene devices using a combination of macroscopic DC transport measurement and the local Scanning Gate Microscopy (SGM) technique
Summary
Graphene has received much attention in recent years due to its unique electronic properties. Transformations in the band structure lead to a work function difference of ∼120 ± 15 meV between 1LG and 2LG [5,6,7], which in general depends on the growth conditions, substrate, environmental doping, etc. These differences in the work function, reflecting the variation in the carrier concentrations in 1LG and 2LG, can significantly affect the transport properties of graphene devices and, their performance in electronic applications. A possibility to open a band gap on applying of an out-of-plane electric field has been experimentally and theoretically explored in AB-stacked 2LG [8, 9]
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