| This dissertation presents the experimental and theoretical investigation of thermal transport in the advanced engineered materials for thermal management of nanoscale devices. Heat dissipation in downscaled transistors became a major challenge for the high-performance microprocessors. It is important to understand the specifics of heat propagation in the nanostructured and disordered materials proposed for the use in the next generation of integrated circuits. The materials studied in this dissertation include epitaxially grown Ge/Si quantum dot superlattices (QDS), diamond-like carbon (DLC) thin films, undoped and nitrogen-doped nanocrystalline diamond (NCD) films. Thermal transport through silicon-on-insulator (SOI), poly-Si and silicide, as well as thermal crosstalk in SOI-based transistors have also been investigated. The thermal conductivity measurements presented in this dissertation have been performed in the temperature range from 10 K to 400 K using the 3o technique. The results show that the thermal conductivity in Ge/Si QDS can be reduced by ∼90% from its bulk value. While such reduction is desirable for the applications in the solid-state micro-cooling and thermoelectric energy conversion it is detrimental in conventional electronic devices. A comprehensive thermal study has been carried out for DLC films with a broad range of structural parameters, H content and thicknesses. The obtained results show that in DLC films, both the amount of sp3 and sp2 phases as well as their ordering play an important role in defining thermal conduction. In NCD films, the grain boundaries and the grain size radically affect the phonon conduction. Nitrogen incorporation affects the phonon transport both, directly through Rayleigh scattering and, indirectly, by changing the grain boundary, size and geometry. The experimental results obtained for Si/Ge QDS and nanocrystalline diamond films have been explained with the help of the phonon-hopping model. The effect of the material properties on thermal cross-talk has been investigated both experimentally and numerically on the example of the field-effect transistors implemented on SOI substrates. It was discovered that the thermal crosstalk is surprisingly high even for devices with the shallow-trench isolation (STI) structure. This effect has been explained with the help of the finite-elements calculations, which indicated heat shunting of STI through the substrate. |
