Dilute isovalent sulfur doping simultaneously increases electrical conductivity and Seebeck coefficient in Bi2 Te2 Se nanoplates, and bulk pellets made from them. This unusual trend at high electron concentrations is underpinned by multifold increases in electron effective mass attributable to sulfur-induced band topology effects, providing a new way for accessing a high thermoelectric figure-of-merit in topological-insulator-based nanomaterials through doping.
We report a 13-fold increase in electrical contact conductivity Σc upon introducing a 1,8-octanedithiol (ODT) monolayer at Cu-Bi2Te3 interfaces. In contrast introducing ODT at Ni-Bi2Te3 interfaces results in a 20% decrease in Σc. Rutherford backscattering spectrometry, X-ray diffraction and electron spectroscopy analyses indicate that metal-sulfur and sulfur-Bi2Te3 bonds at metal-Bi2Te3 interfaces inhibit chemical mixing, curtail metal-telluride formation, and suppress oxidation. Suppressing p-type Cu2Te favors electrical transport across Cu-metallized n-type Bi2Te3, whereas inhibiting the formation of Ohmic-contact-promoting NixTey compromises the electrical conductance at Ni-Bi2Te3 interfaces. Our findings illustrate that molecular nanolayers could be attractive for manipulating interface chemistry and phase formation for tailoring electrical transport across metal-thermoelectric interfaces for solid-state refrigeration applications.
Ab initio predictions indicating that alloying RuO2 with La, Eu, or Lu can increase the Seebeck coefficient α manifold due to quantum confinement effects are validated in sputter-deposited La-alloyed RuO2 films showing fourfold α increase. Combinatorial screening reveals that α enhancement correlates with La-induced lattice distortion, which also decreases the thermal conductivity twentyfold, conducive for high thermoelectric figures of merit. These insights should facilitate the rational design of high efficiency oxide-based thermoelectrics through quantum-guided alloying.
Tailoring electrical and thermal contact conductivities (Σc and Γc) across metallized pnictogen chalcogenide interfaces is key for realizing efficient thermoelectric devices. The authors report that Cu, Ni, Ti, and Ta diffusion and interfacial telluride formation with n-Bi2Te3 and p-Sb2Te3 influence both Σc and Γc. Cu metallization yields the highest Γc and the lowest Σc, correlating with maximal metal diffusion and copper telluride formation. Ni diffuses less and yields the highest Σc with Sb2Te3 due to p-type nickel telluride formation, which diminishes Σc improvement with n-Bi2Te3 interfaces. Ta and Ti contacts yield the lowest properties similar to that in Ni-metallized structures. These correlations between interfacial diffusion and phase formation on electronic and thermal transport properties will be important for devising suitable metallization for thermoelectric devices.
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