  Atomically thin monolayers of graphene show excellent electronic properties
which have led to a great deal of research on their use in nanoscale devices.
However, heat management of such nanoscale devices is essential in order to
improve their performance. Graphene supported on hexagonal boron nitride (h-BN)
substrate has been reported to show enhanced (opto)electronic and thermal
properties as compared to extensively used SiO2/Si supported graphene.
Motivated by this, we have performed temperature- and power-dependent Raman
Spectroscopic measurements on four different types of (hetero)structures: (a)
h-BN (BN), (b) graphene (Gr), (c) h-BN on graphene (BG), and (d) graphene
encapsulated by h-BN layers from both top and bottom (BGB), all supported on
SiO2/Si substrate. We have estimated the values of thermal conductivity
(\k{appa}) and interfacial thermal conductance per unit area (g) of these four
(hetero)structures to demonstrate the structure-activity (thermal)
relationship. We report here the values of \k{appa} and g for h-BN supported on
SiO2/Si as 280.0
  +-58.0 Wm-1K-1 and 25.6+-0.4 MWm-2K-1, respectively. More importantly, we
have observed an improvement in both thermal conductivity and interfacial
thermal conductance per unit area in the heterostructures which ensures a
better heat dissipation in devices. The \k{appa} and g of h-BN encapsulated
graphene on SiO2/Si (BGB) sample was observed to be 850.0+-81.0 Wm-1K-1 and
105+-1 MWm-2K-1, respectively, as opposed to 600.0+-93.0 Wm-1K-1 and 1.15+-0.40
MWm-2K-1, respectively, for graphene on SiO2/Si substrate. Therefore, we
propose that for graphene-based nanoscale devices, encapsulation with h-BN is a
better alternative to address heat management issues.
