Thermal Transport in Disordered Materials

ABSTRACT

We review the status of research on thermal/phonon transport in disordered materials. The term disordered materials is used here to encompass both structural and compositional disorder. It includes structural deviations ranging from an ideal crystal with disordered arrangements of defects all the way to fully amorphous materials, as well as crystals with impurities up through multi-component random alloys. Both types of disorder affect phonons by breaking the symmetry of an idealized crystal and changing their character/mode shapes. These effects have important implications with regard to phonon–phonon interactions, phonon transport and phonon interactions with other quantum particles, which are being actively investigated. Herein, we synthesize the current theoretical understanding, identify the aspects of the problem that require more work, and pose open questions. Abbreviations: BTE: Boltzmann transport equation; DFT: Density functional theory; EPP: Eigenvector periodicity parameter; FAFDTR: Fiber-aligned frequency domain thermoreflectance; GK: Green–Kubo; GKMA: Green–Kubo modal analysis; HCACF: Heat current autocorrelation function; IXS: Inelastic X-ray scattering; LD: Lattice dynamics; LJ: Lennard–Jones; MD: Molecular dynamics; MFP: Mean free path; NEMD: Non-equilibrium molecular dynamics; NMD: Normal-mode dynamics; PDL: Propagon, diffuson, locon; PGM: Phonon gas model; PR: Participation ratio; SCLD: Supercell lattice dynamics; SED: Spectral energy density; TDTR: Time-domain thermoreflectance; VCA: Virtual crystal approximation;     

Thermal convection of MHD Blasius and Sakiadis flow with thermal convective conditions and variable properties

Microsystem Technologies - A theoretical study on the effect of magnetohydrodynamic field on the classical Blasius and Sakiadis flows of heat transfer characteristics with variable conditions and...     

Reliability of fine-pitch through-vias in glass interposers and packages for high-bandwidth computing and communications

Glass is an ideal substrate material to enable 2.5D and 3D packaging of ICs at low cost and high performance. However, it is a brittle material and is prone to failures during fabrication and operation. Large coefficient of thermal expansion (CTE) mismatch between copper and glass leads to thermomechanical stresses that can lead to glass cracking and delamination from glass interfaces. This paper focuses on modeling and reliability characterization of copper-plated through-package-vias (TPV) in glass packages. Thermomechanical simulations were carried out to obtain design guidelines for reliable TPVs in glass. Test-vehicles with different glass thicknesses and copper TPV fabrication conditions were fabricated for thermal cycling tests, resistance monitoring and failure analysis. The reliability characterization results showed good thermomechanical reliability of TPVs in ultra-thin glass panels.     

On the Role of Contact Resistance and Electrode Modification in Organic Electrochemical Transistors

Contact resistance is renowned for its unfavorable impact on transistor performance. Despite its notoriety, the nature of contact resistance in organic electrochemical transistors (OECTs) remains unclear. Here, by investigating the role of contact resistance in n‐type OECTs, the first demonstration of source/drain‐electrode surface modification for achieving state‐of‐the‐art n‐type OECTs is reported. Specifically, thiol‐based self‐assembled monolayers (SAMs), 4‐methylbenzenethiol (MBT) and pentafluorobenzenethiol (PFBT), are used to investigate contact resistance in n‐type accumulation‐mode OECTs made from the hydrophilic copolymer P‐90, where the deliberate functionalization of the gold source/drain electrodes decreases and increases the energetic mismatch at the electrode/semiconductor interface, respectively. Although MBT treatment is found to increase the transconductance three‐fold, contact resistance is not found to be the dominant factor governing OECT performance. Additional morphology and surface energy investigations show that increased performance comes from SAM‐enhanced source/drain electrode surface energy, which improves wetting, semiconductor/metal interface quality, and semiconductor morphology at the electrode and channel. Overall, contact resistance in n‐type OECTs is investigated, whilst identifying source/drain electrode treatment as a useful device engineering strategy for achieving state of the art n‐type OECTs.     

An information supply chain system view for managing rare infectious diseases: The need to improve timeliness

Timely reporting of rare infectious disease cases to the public health system, especially after identification at laboratories, is essential to initiate quick and effective public health response. To ensure that the public health reporting system is appropriately monitoring the rare infectious diseases under surveillance, it is recommended to have a regular assessment of timeliness, especially after the rare infectious case is confirmed. This study aimed to evaluate the timeliness of data reported to the Ohio Disease Reporting System (ODRS), a public health reporting system in Ohio, for managing rare infectious diseases. In a cross-sectional analysis of rare infectious disease reporting data in four local health jurisdictions (LHJs) in the state of Ohio, wide delays were found between various reporting steps, particularly when the laboratories were not using the electronic method of reporting, and the delay observed was mainly at the hospital level and at the LHJ level. This study highlights the supply chain nature of information transfer and calculates the delay at various interacting points of the information supply chain system. The results establish that a centralized approach with an electronic disease reporting system conveys information faster than traditional reporting channels (decentralized approach). Delays of the decentralized approach are isolated at various stakeholder levels and with respect to various types of rare infectious diseases for better understanding of the information supply chain system for managing rare infectious diseases.     

Contact-Barrier Free,High Mobility,Dual-Gated Junctionless Transistor Using Tellurium Nanowire

The gate-all-around nanowire transistor, due to its extremely tight electrostatic control and vertical integration capability, is a highly promising candidate for sub-5 nm technology nodes. In particular, the junctionless nanowire transistors are highly scalable with reduced variability due to avoidance of steep source/drain junction formation by ion implantation. Here a dual-gated junctionless nanowire p-type field effect transistor is demonstrated using tellurium nanowire as the channel. The dangling-bond-free surface due to the unique helical crystal structure of the nanowire, coupled with an integration of dangling-bond-free, high quality hBN gate dielectric, allows for a phonon-limited field effect hole mobility of 570 cm² V⁻¹ s⁻¹ at 270 K, which is well above state-of-the-art strained Si hole mobility. By lowering the temperature, the mobility increases to 1390 cm² V⁻¹ s⁻¹ and becomes primarily limited by Coulomb scattering. The combination of an electron affinity of ≈ 4 eV and a small bandgap of tellurium provides zero Schottky barrier height for hole injection at the metal-contact interface, which is remarkable for reduction of contact resistance in a highly scaled transistor. Exploiting these properties, coupled with the dual-gated operation, we achieve a high drive current of 216 μA μm⁻¹ while maintaining an on-off ratio in excess of 2 × 10⁴. The findings have intriguing prospects for alternate channel material based next-generation electronics.     

Engineering Aggregation-Resistant MXene Nanosheets As Highly Conductive and Stable Inks for All-Printed Electronics

MXenes are interesting 2D materials that have been considered as attractive frontier materials for potential applications in the fields of energy and electronic devices due to their excellent optoelectronic properties including metallic conductivity and high optical transparency. However, it is still challenging to achieve compatibility for the as-synthesized MXene nanosheets with simple solution-deposition and patterning processes because of their limited solubility in many solvents. Here, a promising strategy is developed for obtaining alcohol-dispersible MXene nanosheets suitable for all-printed electronics while enhancing their electrical conductivity. This strategy includes a trifluoroacetic acid treatment—applied in order to contribute to the modification of intercalants between the MXene nanosheets—and achieves long-term dispersion of the MXene in alcoholic media and balanced jetting conditions during the electrohydrodynamic printing process. Furthermore, the high conductivity levels of the treated MXenes allow their printed patterns to be applied as gate and source/drain electrodes in all-printed logic circuits, displaying good and robust operation in transistors, inverters, and NAND, and NOR logic gates. This study provides a promising approach for modifying MXene nanosheets with the purpose of achieving desirable properties suitable for large-area printing processes, suggesting the feasibility of using MXene in practical applications involving all-printed electronics.