Thermal Properties of Graphene and Carbon Based Materials: Prospects of Thermal Management Applications
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Thermal Properties of Graphene and Carbon Based Materials: Prospects of Thermal Management Applications Suchismita Ghosh1 and Alexander A. Balandin2 1 Intel Corporation, Hillsboro OR 97124, U.S.A. 2 Nano-Device Laboratory, Electrical Engineering Department and Materials science and Engineering Program, University of California Riverside, Riverside, CA 92521, U.S.A. ABSTRACT In recent years, there has been an increasing interest in thermal properties of materials. This arises mostly from the practical needs of heat removal and thermal management, which have now become critical issues for the continuing progress in electronic and optoelectronic industries. Another motivation for the study of thermal properties at nanoscale is from a fundamental science perspective. Thermal conductivity of different allotropes of carbon materials span a uniquely large range of values with the highest in graphene and carbon nanotube and the lowest in amorphous or disordered carbon. Here we describe the thermal properties of graphene and carbon-based materials and analyze the prospects of applications of carbon materials in thermal management. INTRODUCTION As the electronic device feature size approaches a few-nanometer length scale, the increased power densities and high chip temperature hinders reliable performance of integrated circuits [12, 3]. While this is an issue at the chip level and posing a problem for the circuit designers, device designers have started facing problems within individual transistors and this gives rise to thermal management issues. For a wide range of devices such as complementary metal-oxide silicon CMOS and high electron mobility transistors, excessive heating severely impedes the operations. One of the main reasons behind this is the nanoscale device feature size approaching the phonon mean free path (MFP). At such a length scale, phonon boundary scattering starts dominating the three phonon Umklapp scattering. Acoustic phonons having large group velocities are the ones which contribute mostly to thermal conductivity as opposed to optical phonons with smaller group velocity. When conventional design is power constrained, in order to maintain optimum device performance, one has to take into account engineering of material parameters or structural geometry so that heat can be removed efficiently. One possible solution to the thermal issues is to find a material with very high thermal conductivity so that it can be integrated with Si based complementary metal-oxide-semiconductor (CMOS) technology and three-dimensional (3D) electronics for efficient heat removal [4]. There has been a growing interest in the thermal transport of individual nanostructures as well as nanostructure-based devices. A material’s heat conduction ability is ingrained in its atomic structure and study of thermal properties of nanostructures can elucidate basic materialcharacteristics. Thermal transport at nanoscale is significantly different from that as macroscale [5]. Owing to increased phonon boundary scattering and changes in phonon
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