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Transient thermal response of a nanoscale hot-spot in a film with alternating materials

An alternative model stemmed from the Boltzmann transport equation, the lattice Boltzmann method (LBM), is developed to successfully capture the transient thermal profile in a sub-continuum domain at a reduced computational cost. A film with alternating materials with different thermal characteristics is chosen to examine the transient thermal profile under the influence of a nanoscale hot-spot. For non-equilibrium conditions, the conventional definition of temperature breaks done so an equivalent temperature at which the total equilibrium energy of system is equal to the actual thermal energy. In order to efficiently formulate boundary effects which are useful in generalizing isolated domain to an alternating film, ghost particles are introduced. To simulate metallic solids, multi-grid simulation technique is used to simultaneously solve couple lattice Boltzmann equation for electrons and phonons. Simulation results show that reduction of the system size from the continuum to the sub-continuum domain, Fourier equation increasingly under-predict the peak temperature rise at the center of the hot-spot. Reducing the characteristic length, the sub-continuum effect of hot-spot confinement and high temperature rise is captured by LBM simulation while Fourier equation fails to capture these phenomena. For an alternating film case, the hot-spot in one domain interfere with the neighboring domains in a complex manner and domain interfaces strongly affect the thermal profile of the system.