7 research outputs found
Effect of charged impurities on graphene thermoelectric power near the Dirac point
In graphene devices with a varying degree of disorders as characterized by
their carrier mobility and minimum conductivity, we have studied the
thermoelectric power along with the electrical conductivity over a wide range
of temperatures. We have found that the Mott relation fails in the vicinity of
the Dirac point in high-mobility graphene. By properly taking account of the
high temperature effects, we have obtained good agreement between the Boltzmann
transport theory and our experimental data. In low-mobility graphene where the
charged impurities induce relatively high residual carrier density, the Mott
relation holds at all gate voltages
Spin Relaxation in Single Layer Graphene with Tunable Mobility
Graphene is an attractive material for spintronics due to theoretical
predictions of long spin lifetimes arising from low spin-orbit and hyperfine
couplings. In experiments, however, spin lifetimes in single layer graphene
(SLG) measured via Hanle effects are much shorter than expected theoretically.
Thus, the origin of spin relaxation in SLG is a major issue for graphene
spintronics. Despite extensive theoretical and experimental work addressing
this question, there is still little clarity on the microscopic origin of spin
relaxation. By using organic ligand-bound nanoparticles as charge reservoirs to
tune mobility between 2700 and 12000 cm2/Vs, we successfully isolate the effect
of charged impurity scattering on spin relaxation in SLG. Our results
demonstrate that while charged impurities can greatly affect mobility, the spin
lifetimes are not affected by charged impurity scattering.Comment: 13 pages, 5 figure