Nanoscale novel devices have raised the demand for nanoscale thermal characterization that is critical for evaluating the device performance and durability. Achieving nanoscale spatial resolution and high accuracy in temperature measurement is very challenging due to the limitation of measurement pathways. In this review, we discuss four methodologies currently developed in nanoscale surface imaging and temperature measurement. To overcome the restriction of the conventional methods, the scanning thermal microscopy technique is widely used. From the perspective of measuring target, the optical feature size method can be applied by using either Raman or fluorescence thermometry. The near-field optical method that measures nanoscale temperature by focusing the optical field to a nano-sized region provides a non-contact and nondestructive way for nanoscale thermal probing. Although the resistance thermometry based on nano-sized thermal sensors is possible for nanoscale thermal probing, significant effort is still needed to reduce the size of the current sensors by using advanced fabrication techniques. At the same time, the development of nanoscale imaging techniques, such as fluorescence imaging, provides a great potential solution to resolve the nanoscale thermal probing problem. Keywords: nanoscale; scanning thermal microscopy; feature size; near-field; Raman spectroscopy; near-field; resistance thermometry (Published: 12 March 2012) Citation: Nano Reviews 2012, 3: 11586 - DOI: 10.3402/nano.v3i0.11586

Thermal transport in graphene and graphene nanostructures have been studied experimentally and theoretically. Methods and previous work to measure and calculate the thermal conductivities of graphene and related nanostructures are briefly reviewed. We demonstrate that combining Raman spectroscopy for thermometry and electrical transport for Joule heating is an effective approach to measure both graphene thermal conductivity and graphene-substrate interface thermal resistance. This technique has been applied to a variety of exfoliated or CVD-grown graphene samples (both suspended and substrate-supported), yielding values comparable with those measured using all-optical or all-electrical techniques. We have also employed classical molecular dynamics simulation to study thermal transport in graphene nanostructures and suggest such structures may be used as promising building blocks for nanoscale thermal engineering.

As the dimensions of nanocircuits and nanoelectronics shrink, thermal energies are being generated in more confined spaces, making it extremely important and urgent to explore for efficient heat dissipation pathways. In this work, the phonon energy transport across graphene and hexagonal boron-nitride (h-BN) interface is studied using classic molecular dynamics simulations. Effects of temperature, interatomic bond strength, heat flux direction, and functionalization on interfacial thermal transport are investigated. It is found out that by hydrogenating graphene in the hybrid structure, the interfacial thermal resistance (R) between graphene and h-BN can be reduced by 76.3%, indicating an effective approach to manipulate the interfacial thermal transport. Improved in-plane/out-of-plane phonon couplings and broadened phonon channels are observed in the hydrogenated graphene system by analyzing its phonon power spectra. The reported R results monotonically decrease with temperature and interatomic bond strengths. No thermal rectification phenomenon is observed in this interfacial thermal transport. Results reported in this work give the fundamental knowledge on graphene and h-BN thermal transport and provide rational guidelines for next generation thermal interface material designs.