Full text loading...
STM images and apparent height of stacked graphene flakes on the graphene/Ru substrate. (a) A flake sitting on top of the first graphene layer shows a STM apparent height of ∼1.8 Å, obtained with sample bias voltage V s = −15 mV and tunneling current I t = 0.5 nA. The inset shows an expanded view of the atomic lattice structure of the first layer, and the second layer is in registry with it. 24 Adapted with permission from Ref. 24 . Copyright 2013 American Chemical Society. (b) Similar result is observed for another flake with V s = −1.5 V and I t = 5 pA, which presents the same apparent height. (c) A bilayer stacking of flakes shows a total height of 4.5 Å, the third layer flake adding 2.7 Å. (d) A trilayer stacking of flakes shows a total height of 7.8 Å, indicating that the fourth layer adds another 3.3 Å. The first to fourth graphene layers are labeled “1 L” to “4 L,” respectively.
(a) Sketch showing the measurement of apparent height of each successive layer in stacked graphene flakes. (b) Schematic plot of the derived doping level in the graphene flakes on Ru, where E F is the Fermi level and E D is the Dirac point. The strong doping effect in the first layer by Ru is attenuated in the second one, and almost eliminated in the third and fourth layer.
Graphene flakes on a graphene/Cu(111) substrate. (a) STM image, obtained with V s = −380 mV and I t = 15 pA, showing flakes sitting on thefirst graphene layer on Cu. 23 Adapted with permission from Ref. 23 . Copyright 2012 American Chemical Society. (b) Expanded view of the area encircled by rectangle in (a), revealing the atomic structure of the graphene layer. (c) Height profile along the line in (a), indicating an apparent height of ∼1.9 Å for the second-layer flake.
A water layer intercalated between the graphene and Ru effectively blocks the charge transfer from Ru. (a) STM image showing a flake sitting on the water-intercalated graphene area (the smooth region without Moiré pattern). (b) Height profile along the traced line in (a), indicating an apparent height of ∼3.3 Å for the second-layer flake. (c) Schematic illustration showing the profile of the water-intercalated graphene region.
Article metrics loading...