Quasi continuous wave laser sintering of Si-Ge nanoparticles for thermoelectrics

摘要

Silicon-germanium is an important thermoelectric material for high temperature applications. In this study, thin films composed of SiGe nanoparticles were synthesized in a plasma reactor and sintered by a millisecond pulse width, quasi continuous wave, near infrared laser of wavelength 1070 nm. We demonstrate that laser sintered SiGe thin films have high electrical and low thermal conductivity, dependent on the surface morphology and dopant concentration. Substrate wetting of laser heating induced molten SiGe was found to play an important role in the final surface morphology of the films. Interconnected percolation structures, formed when proper substrate wetting occurs, were found to be more conductive than the balling structure that formed with insufficient wetting. Laser power was adjusted to maximize dopant reactivation while still minimizing dopant evaporation. After optimizing laser sintering process parameters, the best electrical conductivity, thermal conductivity, and Seebeck coefficient were found to be 70.42 S/cm, 0.84 W/m K, and 133.7 mu V/K, respectively. We demonstrate that laser sintered SiGe thin films have low thermal conductivity while maintaining good electrical conductivity for high temperature thermoelectric applications. Published by AIP Publishing.