Thermal conductivity measurements of ultra-thin single crystal silicon layers

Self-heating in deep submicron transistors (e.g., silicon-on-insulator and strained-Si) and thermal engineering of many nanoscale devices such as nanocalorimeters and high-density thermomechanical data storage art strongly influenced by thermal conduction in ultra-thin silicon layers. The lateral thermal conductivity of single-crystal silicon layers of thicknesses 20 and 100 nm at temperatures between 30 and 450 K are measured using joule heating and electrical-resistance thermometry in suspended microfabricated structures. In general, a large reduction in thermal conductivity resulting front phonon-boundary scattering is observed. Thermal conductivity of the 20 nm thick silicon layer at room temperature is nearly 22 W m(-1) K-1, compared to the bulk value, 148 W m(-1) K-1. The predictions of the classical thermal conductivity theory that accounts for the reduced phonon mean free paths based oil a solution of the Boltzmann transport equation along a layer agrees well with the experimental results.