Search

Abstract: This study investigates and demonstrates the enhancement in thermoelectric power factor for n-type AlZnO/InAlZnO multilayer quantum wells as compared to their counterpart bulk films. A 10–20% improvement is observed for operating temperatures <700°C. Fabricated structures are composed of 50 periods, with targeted individual layer thicknesses of 10nm. The best performing multilayer shows an electrical resistivity and Seebeck coefficient of 1000μV/K and at 700°C. In addition, a theoretical relationship is derived between the thermoelectric performance and correlating microstructure that demonstrates the deterioration of electronic transport properties at increased interface roughness levels. To determine the microstructure and interface roughness of the films, X-ray and spectroscopy techniques were used. The proposed model is based on how quantum well-width fluctuations caused by increased interface roughness leads to the localization of carriers and thus a decrease in electrical conductivity. [Copyright &y& Elsevier]

Abstract: An improvement in the thermoelectric power factor of Al doped ZnO has been achieved by means of co-doping with indium using a dual magnetron sputtering system. The concentration of indium in the film was varied from 0 to 10 atomic % by varying the RF power of the In target, with the ZnO:Al target fixed at 100W. It has been found that the films with In concentrations at or below 5at.% have no significant change in microstructure, and yet a marked improvement in thermopower. At higher doping levels, the Seebeck coefficient continues to increase, however poly-crystallinity is induced in the ZnO matrix which results in a considerable decrease in electrical conductivity. This factor ultimately has a negative impact on the materials power factor. Taking into account the films studied, (ZnO)Al.03In.02 exhibited the best thermoelectric properties with an electrical conductivity of 5.88×102 S/cm and a Seebeck coefficient of −220μV/K at 975K, resulting in a power factor is 22.1×10−4 Wm−1 K−2, which is three times greater than for the film with no In doping. Film microstructure, composition, and thermal stability were investigated using X-ray diffraction, scanning electron microscopy, and Auger electron spectroscopy. [ABSTRACT FROM AUTHOR]

The cross-plane thermal conductivity of 22 nm period Si/SiC amorphous multilayer films deposited by magnetron sputtering and measured using a differential 3ω method was found to decrease from 2.0 W/mK at 300 K to 1.1 W/mK at 80 K. Structural disorder in each of the constituent layers of the amorphous multilayer films was confirmed by high resolution transmission electron microscopy. Estimations of the relative contributions of interface and intrinsic layer thermal resistance based on microscopic phonon transport models indicate that mean free path reductions induced by the structural disorder within the multilayer films are responsible for the observed experimental trends. [ABSTRACT FROM AUTHOR]