Thermal conductivity in radial and planar Si/SiOx hybrid nanomembrane superlattices
Although silicon has been widely used in modern electronic devices, its implementation in thermoelectric applications is still hindered due to its high intrinsic thermal conductivity, which leads to an extremely low energy conversion efficiency. Here, we report substantial reduction in planar thermal conductivities for both radial and planar Si/SiOx hybrid nanomembrane superlattices. By increasing the winding number of radial superlattices the in-plane thermal conductivity decreases continuously. Our results validate the thermal coupling effect among hybrid superlattice structures and shed light on a novel efficient way of managing phonon transport in Si-based devices.
Thermal conductivity of mechanically joined nanomembrane superlattices
Hybrid superlattices consisting of a large number of nanomembranes mechanically stacked on top of each other are fabricated by a roll-up and press-back technique. Measurements reveal a two orders reduction of the cross-sectional heat transport through this nanomembrane superlattice compared to a single nanomembrane layer. The low thermal conductivity has the potential to support on-chip solutions for energy harvesters in e.g. micro-autonomous systems.
When Silicon becomes a better thermal insulator than glass…
Silicon has a high room temperature thermal conductivity, which is important for efficient heat dissipation in microelectronics. At the same time this circumstance is a road-block for thermoelectric applications (which exploit thermal/electric energy conversion). We have now demonstrated that introducing Ge nanostructures in single-crystalline Si leads to thermal conductivities which are lower than any other SiGe alloy, amorphous Si and even glass. The perception of "Nano-Si" opens great opportunities towards development of Si compatible on chip cooling or power generation devices. This work was carried out in collaboration with Université Bordeaux-CNRS, CEA-Grenoble, Fraunhofer-IPM, Max-Planck-Institut für Festkörperforschung and The University of California at Santa Cruz.
G. Pernot et al., Nat. Mater. 9, 491 (2010) URL PDF