Environmental Engineering Reference
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3.4.3.4 Connection angle
Experimentally graphene junctions formed by GNRs with different
connection angles can be produced [56, 59]. We investigate the
influence of connection angle on thermal transport in single-
interface graphene junctions. For convenience, we label these
junctions according to the edge shape and connection angle of the
composedGNRsasshowninFig.3.17a.Forinstance,“ZA90”denotes
asingle-interfacejunctionconstructedbyconnectingZGNRtoAGNR
with the connection angle of 90 . Their thermal conductance as
a function of temperature is presented in Fig. 3.17b. Generally,
the larger the connection angle, the higher thermal conductance.
As the temperature increases, the change in the connection angle
of graphene junctions gives rise to larger differences in thermal
conductance. To evaluate the influence of the connection angle,
we further compare their thermal conductance ratio (
σ 0 ) that
is comparable between different materials and transport systems.
As shown in Fig. 3.17c,
σ
/
σ 0 only slightly increases from 100 K to
500 K. Larger connection angle leads to higher
σ
/
σ
σ 0 . For instance,
/
σ
σ 0 of the “ZZ120” junction is 78% at room temperature, 1.7
times that of “ZZ60”. Our results clearly demonstrate that graphene
junctions with larger connection angles exhibit better thermal-
transport properties. In contrast, the effect of connection angle
on electronic transport is much more complicated [55], because
electrons have more localized distribution and their transport is
sensitiveto the detailed structure.
/
3.4.3.5 Graphene quantum dots
Graphene QDs are believed to offer a new approach to quantum
nanoelectronics. For considering more realistic models of graphene
QDs as proposed in Ref. [53] (Fig. 3.13), we construct graphene QDs
by carving narrow constrictions onto a GNR as shown in Fig. 3.18a.
Their calculated thermal conductance is presented in Fig. 3.18b.
The results show that thermal conductance of graphene QDs is
limited by the width of the narrow constriction. Narrowing the
connecting region of graphene QDs will strongly suppress thermal
conductance of the whole system. The suppression becomes larger
 
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