FeCl₃‐Based Few‐Layer Graphene Intercalation Compounds: Single Linear Dispersion Electronic Band Structure and Strong Charge Transfer Doping

Abstract

Graphene has attracted much attention since its first discovery in 2004. Various approaches have been proposed to control its physical and electronic properties. Here, it is reported that graphene‐based intercalation is an efficient method to modify the electronic properties of few‐layer graphene (FLG). FeCl3 intercalated FLGs are successfully prepared by the two‐zone vapor transport method. This is the first report on full intercalation for graphene samples. The features of the Raman G peak of such FLG intercalation compounds (FLGIC) are in good agreement with their full intercalation structures. The FLGICs present single Lorentzian 2D peaks, similar to that of single‐layer graphene, indicating the loss of electronic coupling between adjacent graphene layers. First principle calculations further reveal that the band structure of FLGIC is similar to single‐layer graphene but with a strong doping effect due to the charge transfer from graphene to FeCl3. The successful fabrication of FLGIC opens a new way to modify properties of FLG for fundamental studies and future applications.

Theory and synthesis of bilayer graphene intercalated with ICl and IBr for low power device applications

“…29 Such a large upshift of the G-peak cannot be due to charge-transfer doping from ICl adsorption alone, but must be due to intercalation of ICl into the BLG flake. 30 Using work done by Das et al, 31 we estimate the Fermi level shift of the BLG-GIC to be ∼ 0.7 eV. This agrees very well with our theoretical predictions using DFT.…”

Theory and synthesis of bilayer graphene intercalated with ICl and IBr for low power device applications

“…29 Such a large upshift of the G-peak cannot be due to charge-transfer doping from ICl adsorption alone, but must be due to intercalation of ICl into the BLG flake. 30 Using work done by Das et al, 31 we estimate the Fermi level shift of the BLG-GIC to be ∼ 0.7 eV. This agrees very well with our theoretical predictions using DFT.…”

Charge transfer doping of graphene without degrading carrier mobility

“…For FeCl 3 doping, our calculations suggest there is no C site puckering, so there will be no Raman D peak and no extra carrier scattering. This is consistent with experiment 26,[35][36][37][38][39][40][41] although a small D peak does appear in some cases. 39,40 The absence of a Raman D peak at 1350 cm À1 in the experimental works for FeCl 3 , 26 confirms that FeCl 3 , MoO 3 , and HNO 3 do not give rise to basal plane defects, 17,20,35 and thus should not increase carrier scattering.…”

Intercalation of Few-Layer Graphite Flakes with FeCl3: Raman Determination of Fermi Level, Layer by Layer Decoupling, and Stability

“…Pos(G) of our FeCl 3 -doped SLG is very close to that reported in Ref. 26, where double G peaks, at∼1612 and∼1623cm −1 were also observed for 3 and 4L samples. Ref.…”

“…If FeCl 3 is only present on a single (inner) side of these layers, we expect the amount of charge transfer to reach at most that of stage-2 GICs. In this case, the corresponding Pos(G) can only shift to ∼1612 cm −1 , i.e ., Pos(G) of FeCl 3 -intercalated stage-2 GICs. − In Figure , the Pos(G) of our FeCl 3 -doped 2 L flakes is ∼1615 cm −1 , very close to that (∼1612 cm −1 ) reported in ref , where double G peaks, at ∼1612 and ∼1623 cm −1 , were also observed for 3 and 4 L samples. Reference argued that FeCl 3 does not adsorb on the top and bottom of their flakes.…”

“…In this case, the corresponding Pos(G) can only shift to ∼1612 cm −1 , i.e ., Pos(G) of FeCl 3 -intercalated stage-2 GICs. − In Figure , the Pos(G) of our FeCl 3 -doped 2 L flakes is ∼1615 cm −1 , very close to that (∼1612 cm −1 ) reported in ref , where double G peaks, at ∼1612 and ∼1623 cm −1 , were also observed for 3 and 4 L samples. Reference argued that FeCl 3 does not adsorb on the top and bottom of their flakes. We note that Pos(G) of the lower energy G band in our 3−4 L FeCl 3 -intercalated flakes (∼1618 cm −1 ) is higher than previously reported for FeCl 3 intercalated stage-2 GICs. − Furthermore, in Figure , Pos(G) of intercalated 2−3 L is ∼1623 and ∼1625 cm −1 , much larger than ∼1615 cm −1 in Figure and ∼1612 cm −1 observed for stage-2 GICs. ,, Therefore, we argue that the top and bottom layers of our FeCl 3 -intercalated 2−4 L have double-face doping.…”

Theory and synthesis of bilayer graphene intercalated with ICl and IBr for low power device applications

“…29 Such a large upshift of the G-peak cannot be due to charge-transfer doping from ICl adsorption alone, but must be due to intercalation of ICl into the BLG flake. 30 Using work done by Das et al, 31 we estimate the Fermi level shift of the BLG-GIC to be ∼ 0.7 eV. This agrees very well with our theoretical predictions using DFT.…”

Charge transfer doping of graphene without degrading carrier mobility

“…For FeCl 3 doping, our calculations suggest there is no C site puckering, so there will be no Raman D peak and no extra carrier scattering. This is consistent with experiment 26,[35][36][37][38][39][40][41] although a small D peak does appear in some cases. 39,40 The absence of a Raman D peak at 1350 cm À1 in the experimental works for FeCl 3 , 26 confirms that FeCl 3 , MoO 3 , and HNO 3 do not give rise to basal plane defects, 17,20,35 and thus should not increase carrier scattering.…”

Intercalation of Few-Layer Graphite Flakes with FeCl3: Raman Determination of Fermi Level, Layer by Layer Decoupling, and Stability

“…Pos(G) of our FeCl 3 -doped SLG is very close to that reported in Ref. 26, where double G peaks, at∼1612 and∼1623cm −1 were also observed for 3 and 4L samples. Ref.…”

“…If FeCl 3 is only present on a single (inner) side of these layers, we expect the amount of charge transfer to reach at most that of stage-2 GICs. In this case, the corresponding Pos(G) can only shift to ∼1612 cm −1 , i.e ., Pos(G) of FeCl 3 -intercalated stage-2 GICs. − In Figure , the Pos(G) of our FeCl 3 -doped 2 L flakes is ∼1615 cm −1 , very close to that (∼1612 cm −1 ) reported in ref , where double G peaks, at ∼1612 and ∼1623 cm −1 , were also observed for 3 and 4 L samples. Reference argued that FeCl 3 does not adsorb on the top and bottom of their flakes.…”

“…In this case, the corresponding Pos(G) can only shift to ∼1612 cm −1 , i.e ., Pos(G) of FeCl 3 -intercalated stage-2 GICs. − In Figure , the Pos(G) of our FeCl 3 -doped 2 L flakes is ∼1615 cm −1 , very close to that (∼1612 cm −1 ) reported in ref , where double G peaks, at ∼1612 and ∼1623 cm −1 , were also observed for 3 and 4 L samples. Reference argued that FeCl 3 does not adsorb on the top and bottom of their flakes. We note that Pos(G) of the lower energy G band in our 3−4 L FeCl 3 -intercalated flakes (∼1618 cm −1 ) is higher than previously reported for FeCl 3 intercalated stage-2 GICs. − Furthermore, in Figure , Pos(G) of intercalated 2−3 L is ∼1623 and ∼1625 cm −1 , much larger than ∼1615 cm −1 in Figure and ∼1612 cm −1 observed for stage-2 GICs. ,, Therefore, we argue that the top and bottom layers of our FeCl 3 -intercalated 2−4 L have double-face doping.…”

Theory and synthesis of bilayer graphene intercalated with ICl and IBr for low power device applications

“…29 Such a large upshift of the G-peak cannot be due to charge-transfer doping from ICl adsorption alone, but must be due to intercalation of ICl into the BLG flake. 30 Using work done by Das et al, 31 we estimate the Fermi level shift of the BLG-GIC to be ∼ 0.7 eV. This agrees very well with our theoretical predictions using DFT.…”

Charge transfer doping of graphene without degrading carrier mobility

“…For FeCl 3 doping, our calculations suggest there is no C site puckering, so there will be no Raman D peak and no extra carrier scattering. This is consistent with experiment 26,[35][36][37][38][39][40][41] although a small D peak does appear in some cases. 39,40 The absence of a Raman D peak at 1350 cm À1 in the experimental works for FeCl 3 , 26 confirms that FeCl 3 , MoO 3 , and HNO 3 do not give rise to basal plane defects, 17,20,35 and thus should not increase carrier scattering.…”

Intercalation of Few-Layer Graphite Flakes with FeCl3: Raman Determination of Fermi Level, Layer by Layer Decoupling, and Stability

“…Pos(G) of our FeCl 3 -doped SLG is very close to that reported in Ref. 26, where double G peaks, at∼1612 and∼1623cm −1 were also observed for 3 and 4L samples. Ref.…”

“…If FeCl 3 is only present on a single (inner) side of these layers, we expect the amount of charge transfer to reach at most that of stage-2 GICs. In this case, the corresponding Pos(G) can only shift to ∼1612 cm −1 , i.e ., Pos(G) of FeCl 3 -intercalated stage-2 GICs. − In Figure , the Pos(G) of our FeCl 3 -doped 2 L flakes is ∼1615 cm −1 , very close to that (∼1612 cm −1 ) reported in ref , where double G peaks, at ∼1612 and ∼1623 cm −1 , were also observed for 3 and 4 L samples. Reference argued that FeCl 3 does not adsorb on the top and bottom of their flakes.…”

“…In this case, the corresponding Pos(G) can only shift to ∼1612 cm −1 , i.e ., Pos(G) of FeCl 3 -intercalated stage-2 GICs. − In Figure , the Pos(G) of our FeCl 3 -doped 2 L flakes is ∼1615 cm −1 , very close to that (∼1612 cm −1 ) reported in ref , where double G peaks, at ∼1612 and ∼1623 cm −1 , were also observed for 3 and 4 L samples. Reference argued that FeCl 3 does not adsorb on the top and bottom of their flakes. We note that Pos(G) of the lower energy G band in our 3−4 L FeCl 3 -intercalated flakes (∼1618 cm −1 ) is higher than previously reported for FeCl 3 intercalated stage-2 GICs. − Furthermore, in Figure , Pos(G) of intercalated 2−3 L is ∼1623 and ∼1625 cm −1 , much larger than ∼1615 cm −1 in Figure and ∼1612 cm −1 observed for stage-2 GICs. ,, Therefore, we argue that the top and bottom layers of our FeCl 3 -intercalated 2−4 L have double-face doping.…”