Ultra-low thermal conductivity in nanoscale, epitaxial SnS grains

Thermally insulating nanoscale building blocks enable efficient routes to both passive and active heat management in miniaturized architectures. However, identifying suitable nanomaterials by computational and experimental means is difficult as critical dimensions reach the scale of thermal carriers and thermal interfaces become dominant. In this work, we propose epitaxially grown layered SnS as an outstanding thermal insulator at the thin film limit. The challenge of measuring heat transport at the nanoscale was tackled by locally probing out-of-plane thermal transport on grains of varying thickness utilizing scanning thermal microscopy. We consistently find an ultra-low thermal conductivity value of 45 mWm−1K−1, which is among the lowest reported for dense solids to date. This finding challenges previous predictions of the SnS system and opens up promising prospects for its integration into heat management components.