Figure 2
(a) Many graphene devices exhibited no sign of weak localization or antilocalization. Solid curves correspond to gate voltages shown by arrows in Fig. 1 (
, 20, and 50 V from top to bottom curve, respectively). The curves are shifted for clarity (
, 0.8, and
from top to bottom). The lowest curve corresponds to
. Notice magnification factors for the
scale against each of the curves. These factors were chosen so that the expected WL peak for all the curves would be of approximately the same size as the peak shown by the dashed curve calculated using the standard WL theory [
11,
12]. (b) Magnetoresistance behavior at zero
where
reaches its maximum
. For such high resistivity (i.e.,
per each type of carriers), a metal-insulator transition is generally expected but it does not occur in the case of graphene [
2]. Both absolute value of
and its magnetoresistance
are practically temperature independent below 100 K. (c) Multilayer films [
10] exhibited the standard weak-localization behavior. Shown is a device with
and mobility
(no gate voltage applied). A clear WL peak is seen at zero
. In higher fields, multilayer devices exhibit a large linear (
) magnetoresistance. All curves shown in Fig. 2 were measured at 4 K.
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