Effect of molecular length on the electrical conductance across metal-alkanedithiol-Bi_2Te_3 interfaces

摘要

Controlling electronic transport across metal-thermoelectric interfaces is important for realizing high-efficiency solid-state refrigeration and waste-heat harvesting devices. We report up to 34-fold increase in electrical contact conductivity Σ_c across Cu-alkanedithiol-Bi_2Te_3 interfaces. Longer chain dithiols are more effective in curtailing Cu diffusion, telluride formation, and reducing inter-facial oxides of Bi and Te, leading to higher Σ_c. In contrast, Σ_c is insensitive to the alkanedithiol chain length at Ni-alkanedithiol-Bi_2Te_3 interfaces due to weak Ni-S bonding. These results indicate that interfacial bonding and phase formation are primary determinants of Σ_c rather than charge transport through the alkanedithiol molecules. Our findings provide insights for tuning electronic transport across metal-thermoelectric interfaces using an interfacial nanolayer comprising molecules with suitably chosen chemical termini and molecular length.