Oral Graphene and carbon nanotube thermoelectric transducers

Abstract

Basic understanding of fundamental mechanisms the thermal and electric transport on nanoscale is required for newapproaches and methodologies. Thermoelectric phenomena have a strong potential for the local cooling on the nano-scale,enabling to exploit the low-temperature phenomena at room temperatures with no needs in bulky and expensive refrigeratingequipment. Thermoelectric cooling is observed in the carbon nanotube (CNT), whose opposite ends contain the charge carriersof opposite sign, either electrons or holes, created by doping with using of the local gate electrodes. Finite source-drain electricbias voltage DV causes change of the local effective electron temperature Te at the middle of CNT, owing to the Peltier effect,whilst the magnitude is deduced from the change in the position and width of spectral singularities, which is manifested in theexperimental curves of the source-drain electric conductance. Depending on the sign of DV, the thermoelectric effect causeseither cooling or heating of the electron subsystem inside CNT, with the Te change ~70 K. The value of deduced figure of meritis ZT~10 and the cooling power density is ~ 80 kW/cm2.The thermal flux Q propagating along the graphene ribbon is determined by the frequency of the electron-restricted phononscattering and depends on concentration of the electric charge carriers nC. By using the electrode doping, nC increases, causinga sharp rise of both the electric conductivity and Seebeck coefficient, while the thermal conductivity tumbles. Such the effect ofthermal transistor improves the figure of merit of the thermoelectric transducing circuits.