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The application of graphene in high-performance thermal management has received a lot of attention in recent years, which still needs further exploration and development. Here, based on first-principles calculations, the thermal transport is found to be efficiently modulated by enhancing interlayer interactions in bilayer graphene (BLG), showing a different trend compared to graphite. The results of our work suggest that, by enhancing the interlayer force, the "in-plane" anharmonic phonon transport of BLG while the "out-of-plane" harmonic phonon transport of graphite can be effectively tuned. By manipulating interlayer interactions, a controllable and directed parameter (6% out-of-plane compressing deformation of BLG can achieve more than 25% decrement of in-plane thermal conductivity; 10% out-of-plane compressing deformation of graphite can increase out-of-plane thermal conductivity by more than 5 times) for tuning the thermal conductivity can be achieved. The difference in the effect of the interlayer force on thermal conductivity for low-dimensional and bulk materials emphasizes the significance of the anharmonic phonon transport properties of low-dimensional materials with interlayer interaction and thereby provides an important insight for promoting the future application of bilayer graphene and graphite. [ABSTRACT FROM AUTHOR]

HfO2, as a kind of high dielectric ceramic material, has important applications in microelectronic devices. With device miniaturization, the intrinsic thermal conductivity and thermal boundary resistance of ultrathin HfO2 films on Si substrate are becoming increasingly important in thermal management related to heat conduction for gate dielectrics on a few nanometer scales. To study the thickness and temperature dependences of the thermal properties, a series of ultrathin HfO2 films with thickness of 2 nm, 6 nm, 10 nm and 20 nm are grown on Si substrates. The intrinsic thermal conductivities and the thermal boundary resistances are simultaneously measured by the two-color femtosecond pump–probe technique between 300 and 500 K. The intrinsic thermal conductivity of the 2 nm film is about 0.13 Wm−1·K−1, and the thermal conductivity of HfO2 is positive correlated to the thickness. The measured thermal boundary conductance is positive correlated to the temperature. The contributions of elastic and inelastic scattering is determined through the anharmonic inelastic model, and the results show that the inelastic scattering plays a nonnegligible role in interfacial thermal transport. [ABSTRACT FROM AUTHOR]

Full Heusler compounds have long been discovered as exceptional n-type thermoelectric materials. However, no p-type compounds could match the high n-type figure of merit (ZT). In this work, based on first-principles transport theory, we predict the unprecedentedly high p-type ZT = 2.2 at 300 K and 5.3 at 800 K in full Heusler CsK2Bi and CsK2Sb, respectively. By incorporating the higher-order phonon scattering, we find that the high ZT value primarily stems from the ultralow lattice thermal conductivity (κL) of less than 0.2 W mK−1 at room temperature, decreased by 40% compared to the calculation only considering three-phonon scattering. Such ultralow κL is rooted in the enhanced phonon anharmonicity and scattering channels stemming from the coexistence of antibonding-induced anharmonic rattling of Cs atoms and low-lying optical branches. Moreover, the flat and heavy nature of valence band edges leads to a high Seebeck coefficient and moderate power factor at optimal hole concentration, while the dispersive and light conduction band edges yield much larger electrical conductivity and electronic thermal conductivity (κe), and the predominant role of κe suppresses the n-type ZT. This study offers a deeper insight into the thermal and electronic transport properties in full Heusler compounds with strong phonon anharmonicity and excellent thermoelectric performance. [ABSTRACT FROM AUTHOR]

Correction for 'First-principles calculations of interfacial thermal transport properties between SiC/Si substrates and compounds of boron with selected group V elements' by Zhehao Sun et al., Phys. Chem. Chem. Phys., 2019, 21, 6011–6020, https://doi.org/10.1039/C8CP07516F. [ABSTRACT FROM AUTHOR]

Zintl phase Mg3Sb2, which has ultra-low thermal conductivity, is a promising anisotropic thermoelectric material. It is worth noting that the prediction and experiment value of lattice thermal conductivity (κ) maintain a remarkable difference, troubling the development and application. Thus, we firstly included the four-phonon scattering processes effect and performed the Peierls–Boltzmann transport equation (PBTE) combined with the first-principles lattice dynamics to study the lattice thermal transport in Mg3Sb2. The results showed that our theoretically predicted κ is consistent with the experimentally measured, breaking through the limitations of the traditional calculation methods. The prominent four-phonon scatterings decreased phonon lifetime, leading to the κ of Mg3Sb2 at 300 K from 2.45 (2.58) W m−1 K−1 to 1.94 (2.19) W m−1 K−1 along the in (cross)-plane directions, respectively, and calculation accuracy increased by 20%. This study successfully explains the lattice thermal transport behind mechanism in Mg3Sb2 and implies guidance to advance the prediction accuracy of thermoelectric materials. [ABSTRACT FROM AUTHOR]

Accurately and directly characterizing the thermal properties of graphene and thin-graphite films (GFs) is of fundamental importance for understanding the heat transport mechanism and of practical interest in possible applications of thermal management. However, due to the lack of experiment data, the mechanism of the thickness dependence of GFs thermal properties has not been fully understood yet. In this study, a 90-nm-thick GF is characterized by the time-domain thermoreflectance method, and the obtained GFs in-plane thermal conductivity and interfacial thermal conductance between GFs and gold are (1354±297) W/(m·K) and (38±6) MW/(m2·K), respectively. Two theoretical models are also applied for comparison and discussion, and we conclude that the influence from the surface perturbation by supporting materials on the phonon transport of graphite nano-films will beyond the near surface layers to the more inner ones. This work not only provides a better understanding of the fundamental mechanisms of the thermal transport size effect in GFs, but also facilitates the possible applications of GFs as heat spreaders in the future. [ABSTRACT FROM AUTHOR]