Complementary and beneficial effects of Sb and Bi codoping in GeTe are shown to generate high thermoelectric figure of merit, zT, of 1.8 at 725 K in Ge1‑x‑y Bi x Sb y Te samples. Sb and Bi codoping in GeTe facilitates the valence band convergence enhancing the Seebeck coefficient as supported by density functional theoretical (DFT) calculations. Further, Sb and Bi codoping in GeTe releases the rhombohedral strain and increases its tendency to be cubic in structure, which ultimately enhances the valence band degeneracy. At the same time, Bi forms nanoprecipitates of size ∼5–20 nm in GeTe matrix and Sb doping increases solid solution point defects greatly, which altogether scatter low-to mid wavelength phonons and result in reduced lattice thermal conductivity down to 0.5 W/mK in the 300–750 K range.

M-N-C centers have garnered tremendous research attention due to a potential replacement to the Pt- group metal based cathode catalysts and is expected to be the integral part of the...

Rational design of efficient electrode materials for fuel cell, water oxidation, and the metal-air battery is now cutting–edge activity in renewable energy research. In this regard, tuning the activity at...

Combining atomically thin layers of van der Waals (vdW) materials in a chosen vertical sequence is an emerging route to create devices with desired functionalities. While this method aims to exploit the individual properties of partnering layers, strong interlayer coupling can significantly alter their electronic and optical properties.Here we explored the impact of the vdW epitaxy on electrical transport in atomically thin molybdenum disulfide (MoS 2 ) when it forms a vdW dimer with crystalline films of hexagonal boron nitride (hBN). We observe a thermal history-dependent long-term (over ∼40 h) current relaxation in the overlap region of MoS 2 /hBN heterostructures, which is absent in bare MoS 2 layers (or homoepitaxial MoS 2 /MoS 2 dimers) on the same substrate. Concurrent relaxation in the low-frequency Raman modes in MoS 2 in the heterostructure region suggests a slow structural relaxation between trigonal and octahedral polymorphs of MoS 2 as a likely driving mechanism that also results in inhomogeneous charge distribution in the MoS 2 layer. Our experiment yields an aspect of vdW heteroepitaxy that can be generic to electrical devices with atomically thin transition-metal dichalcogenides.