Figure 2: Factors contributing to ZT for various Si nanowires. All nanowires are 20 nm in height.
From: Silicon nanowires as efficient thermoelectric materials
a, The temperature dependence of the thermal conductivity κ, presented as κbulk / κnanowire to highlight the improvement that the reduction of κ in nanowires lends to ZT. κbulk values, which are slightly below the true bulk value for Si, are taken from an identically measured 520 nm × 35 nm-sized film. The inset scanning electron microscope micrographs show the region of the device containing the nanowires before (top) and after (bottom) the XeF2 etch to remove the nanowires. b, The temperature dependence of S2 for 20-nm-wide Si nanowires at various p-type doping concentrations (indicated on the graph). Note that the most highly doped nanowires (pink line) yield a thermopower similar to that of bulk Si doped at a lower level. For nanowires doped at slightly higher and slightly lower concentrations than the bulk, S peaks near 200 K. This is a consequence of the one-dimensional nature of the Si nanowires.
