The structural, electronic, and vibrational properties of graphene oxide are studied by employing a particle swarm optimization search along with density functional theory calculations. We report a novel low-energy semiconducting configuration for the C 2 O phase of graphene oxide that consists of a combination of 1,2 and 1,3-epoxides as well as carbonyl functional groups running along the armchair direction. A detailed analysis of the corrugation and bonding reveals unique features of the new conformation in conformity with experimental observations. Our findings shed light on structural and electronic characteristics that are essential for future improvement of graphene-based nanodevices.
CVD graphene growth typically uses commercially available cold-rolled copper foils, which includes a rich topography with scratches, dents, pits, and peaks. The graphene grown on this topography, even after annealing the foil, tends to include and reflect these topographic features. Further, the transfer of such CVD graphene to a flat substrate using a polymer transfer method also introduces wrinkles. Here, we examine an electropolishing technique for reducing native foil defects, characterize the resulting foil surface, grow single-crystal graphene on the polished foil, and examine the quality of the graphene for such defects.
A metallic state with a vanishing activation gap, at a filling factor $$\nu = 8/5$$
ν
=
8
/
5
in the untilted specimen with $$n= 2 \times 10^{11} cm^{-2}$$
n
=
2
×
10
11
c
m
-
2
, and at $$\nu = 4/3$$
ν
=
4
/
3
at $$n=1.2 \times 10^{11} cm^{-2}$$
n
=
1.2
×
10
11
c
m
-
2
under a $$\theta = 66^{0}$$
θ
=
66
0
tilted magnetic field, is examined through a microwave photo-excited transport study of the GaAs/AlGaAs 2 dimensional electron system (2DES). The results presented here suggest, remarkably, that at the possible degeneracy point of states with different spin polarization, where the 8/5 or 4/3 FQHE vanish, there occurs a peculiar marginal metallic state that differs qualitatively from a quantum Hall insulating state and the usual quantum Hall metallic state. Such a marginal metallic state occurs most prominently at $$\nu =8/5$$
ν
=
8
/
5
, and at $$\nu =4/3$$
ν
=
4
/
3
under tilt as mentioned above, over the interval $$1 \le \nu \le 2$$
1
≤
ν
≤
2
, that also includes the $$\nu = 3/2$$
ν
=
3
/
2
state, which appears perceptibly gapped in the first instance.
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