Ultrahigh thermal isolation across heterogeneously layered two-dimensional materials

phys.org | 8/1/2019 | Staff
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Heterogeneous nanomaterials can now facilitate advanced electronics and photonics applications, but such progress is challenging for thermal applications due to the comparatively shorter wavelengths of heat carriers (known as phonons). In a new study, now published on Science Advances, Sam Vaziri and co-workers at Theiss Research and the departments of Electrical Engineering, Materials Science and Engineering at the National Institute of Standards and Technology (NIST), and the Precourt Institute of Energy at Stanford University, Stanford California, demonstrated unusually high thermal isolation across ultra-thin heterostructures.

They achieved this by layering atomically thin, two-dimensional (2-D) materials to form artificial stacks of monolayer graphene (Gr), molybdenum disulfide (MoS2)and tungsten diselenide (WSe2), with thermal resistance greater than silicon dioxide (SiO2). Alongside effective thermal conductivity lower than air at room temperature. Using Raman thermometry, the scientists simultaneously identified the thermal resistance between any 2-D monolayers in the stack to form thermal metamaterials as examples in the emerging field of phononics. Vaziri et al. propose applications of the metamaterials in ultrathin thermal insulation, thermal energy harvesting and to route heat within ultracompact geometries.

Advanced - Devices - Mobility - Transistors - Quantum

Advanced electronic and photonic devices such as high-electron mobility transistors, quantum cascade lasers and photonic bandgap crystals take advantage of the fermionic nature of charge carriers during voltage gating or confinement. Then they make use of long photon wavelengths during their interference. Nevertheless, thermal nanoengineering and the emerging field of phononics only offer a few examples, despite the existing demand for heat management applications. This discrepancy results from the short wavelengths of heat-carrying vibrations in solids, where the bosonic nature of phonons can also contribute to the challenge of actively controlling heat transport in solids where it cannot be voltage-gated like charge carriers.

Physicists had previously attempted to manipulate the thermal properties of solids using non-laminate films and superlattices to reduce thermal conductivity below the constituent...
(Excerpt) Read more at: phys.org
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