  One of the greatest issues of nanoelectronics today is how to control the
heating of the components. Graphene is a promising material in this area and it
is essential to study its thermal properties. Here, the effect of heating a
bilayer structure was investigated using in situ Raman spectroscopy. In order
to observe the effects on each individual layer, an isotopically labelled
bilayer graphene was synthesized where the two layers are composed of different
carbon isotopes. Therefore, the frequency of the phonons in the Raman spectra
is shifted in relation to each other. This technique was used to investigate
the influence of different stacking order. It was found that in bilayer
graphene grown by chemical vapor deposition (CVD) the two layers behave very
similarly, for both Bernal stacking and randomly oriented structures, while for
transferred samples the layers act more independently. This highlights a
significant dependence on sample preparation procedure.
