Power densities increase and physical dimension tend to shrink in modern integrated electronics. Cooling is also challenged by novel 3D architectures. Thermal management is a bottle-neck discipline where new technologies are urgently required.

Carbon nanotube and graphene have been subjects of investigations for this challenge as they have very high thermal conductivity along its axis and in-plane, respectively. A combination (a hybrid) of the two materials is potentially a very interesting possibility to increase thermal transport. However, the high contact thermal resistance of CNTs and the low through-plane thermal conductivity of graphene presents major roadblocks for their applications in electronics.

We present our recent progress in developing a graphene/CNT-based material with very good thermal properties. When commercial graphite was subjected to CVD multi-walled CNT growth, the thermal resistance between graphene and CNT was measured to be only 9x10-10 m2K/W indicating covalent bond (sp2 bond) between the materials. This is three orders of magnitude lower than the van der Waals contact resistance. The overall through-plane conductivity of the hybrid is at least two orders of magnitude higher than the graphene film itself. 

Experiments with hot-spot cooling and Joule heating showed that temperatures can be decreased significantly with the hybrid material. Pulsed photothermal reflectance measurements indicated a 40 % lower delta-temperature (T) on a chip transistor. Infrared spectroscopy showed a substantial decrease of the T in a Joule heating demonstration with a stand-alone graphene/multi-walled CNT hybrid film.

Power densities increase and physical dimension tend to shrink in modern integrated electronics. Cooling is also challenged by novel 3D architectures. Thermal management is a bottle-neck discipline where new technologies are urgently required.

Carbon nanotube and graphene have been subjects of investigations for this challenge as they have very high thermal conductivity along its axis and in-plane, respectively. A combination (a hybrid) of the two materials is potentially a very interesting possibility to increase thermal transport. However, the high contact thermal resistance of CNTs and the low through-plane thermal conductivity of graphene presents major roadblocks for their applications in electronics.

We present our recent progress in developing a graphene/CNT-based material with very good thermal properties. When commercial graphite was subjected to CVD multi-walled CNT growth, the thermal resistance between graphene and CNT was measured to be only 9x10-10 m2K/W indicating covalent bond (sp2 bond) between the materials. This is three orders of magnitude lower than the van der Waals contact resistance. The overall through-plane conductivity of the hybrid is at least two orders of magnitude higher than the graphene film itself. 

Experiments with hot-spot cooling and Joule heating showed that temperatures can be decreased significantly with the hybrid material. Pulsed photothermal reflectance measurements indicated a 40 % lower delta-temperature (T) on a chip transistor. Infrared spectroscopy showed a substantial decrease of the T in a Joule heating demonstration with a stand-alone graphene/multi-walled CNT hybrid film.