Biography
Biography: Serhii Shafraniuk
Abstract
Conversion of the heat energy directly into electricity and vice versa attracts a significant attention nowadays. Systematic study of thermoelectric phenomena allows for better understanding of the intrinsic mechanisms of the energy transformation and dissipation on the nanoscale. A bias electric voltage ï„V, applied to a conducting sample, pulls the charge carriers, thereby inducing a finite electric current Ie ï€½ï€ Geï„V , where Ge is the electric conductance. Since the bias voltage ï„V also induces an inhomogeneity of charge carrier density along the sample, it leads to a finite temperature difference hot cold ï„T  Thot ï€Tcoldï€ , where T hot(cold) is the temperature of the hot (cold) part of the sample. The thermoelectric effect is described as ï„V  Sï„T where S is a linear-response, two-terminal property known as Seebeck coefficient. Thermoelectric effect is measured using two sequentially-connected carbon nanotube (CNT) field-effect transistors (FETs), each with charge carriers of opposite sign, either electrons or holes, whose concentration is controlled by the side gate electrodes. A change ï„T of the intrinsic temperature is determined from the change of the position and width of spectral singularities manifested in the experimental curves of the source-drain electric conductance. We deduce an impressive Peltier effect ï„T = 57 K inside the CNT associated with cooling and heating, depending on the direction of the electric current. The effect can be utilized for building thermoelectric devices having a figure of merit up to cold ZT ï€½ï€ 7.5  1 and the cooling power density Pcooling~80 kW/cm2.