Professor Shengying Yue from Xi'an Jiaotong University, along with Researcher Lin Yang from the School of Engineering at Peking University, Professor Peng Gao from the School of Physics at Peking University, Engineer Jinlong Du, and others, have collaborated on a study proposing a new strategy to explore the impact of non-uniform stress on thermal conductivity modulation. The recent research findings have been published in "Nature."
The team induced a non-uniform strain field by bending individual silicon nanoribbons (SiNRs) on a homemade suspended microdevice. They utilized scanning transmission electron microscopy electron energy loss spectroscopy (STEM-EELS) with sub-nanometer resolution to characterize the local lattice vibrational spectra. The results revealed that a strain gradient of 0.112% per nanometer led to a significant 34±5% reduction in thermal conductivity (κ), more than three times the modulation achieved under uniform strain in previous literature. This discovery unveiled a unique phonon spectrum broadening effect caused by strain gradients, which resulted in an anomalous suppression of thermal conductivity not observed under uniform stress.
By developing experimental characterization techniques spanning microscale to atomic scale and combining them with first-principles theoretical simulations, this work provides crucial insights into the long-standing challenge of understanding the impact of non-uniform strain on phonon transport. Consequently, this study not only elucidates the modulation mechanism of solid-state thermal conductivity under non-uniform strain but also offers important insights for the innovative design of functional devices based on strain engineering. Furthermore, the modulation of thermal conductivity through non-uniform strain enables the realization of functional thermal switch devices for dynamically controlling heat flux.
For more information on the research paper, visit: https://doi.org/10.1038/s41586-024-07390-4
