Growth of Dense, Vertical and Horizontal Graphene and Its Thermal Properties

We have grown an extremely dense nanocarbon structure on a Si substrate at a temperature of 450 °C, in which vertical graphene layers were formed densely below horizontal graphene layers. We named this carbon structure "dense, vertical, and horizontal graphene (DVHG)". The density of this structure was an extremely high at 1.4 g/cm3, which is 63% of that of graphite (2.2 g/cm3). Although DVHG showed poor thermal properties, we confirmed that vertical thermal conductivity increased by a factor of 10 by removing the horizontal graphene layers from the top of DVHG. This result indicates that the thermal conductivity parallel to the graphene plane is several orders of magnitude higher than that perpendicular to the graphene plane.