Thermoelectric properties of SiGe thin films prepared by laser sintering of nanograin powders

Abstract

Silicon-germanium is an important high-temperature thermoelectric material for thermal to electric energy conversion. This paper focuses on the study of nanograin thermoelectric Si80Ge20 thin films. The nanograin Si80Ge20 thin films were prepared by a novel method of ball milling to generate nanoparticles and sintered by a quasi-continuous wave, near-infrared laser of wavelength 1070 nm. The electrical and thermal properties variations with different laser sintering power were measured, and the sintering mechanism is discussed. The Si/Ge wetting to substrate for a percolation morphology and the control of carrier concentration are found to be the key factors for good electrical conductivity. The stoichiometric ratio of Si and Ge was found to be unchanged in the ball milling and laser sintering process. We demonstrate that the laser sintering was capable of creating well alloyed thermoelectric materials while minimizing grain growth. The thermoelectric parameters like electrical conductivity, thermal conductivity, and figure of merit were measured, and the results are compared with other reported bulk and thin-film studies, and the advantages of our method are discussed. We demonstrate that low-cost nanograin SiGe thin films prepared by ball milling and laser sintering process have a comparable thermoelectric figure of merit to other SiGe thermoelectric materials and which can be further improved.