[7a-C22-1~12] 22.1 Joint Session M "Phonon Engineering"

▲ [7a-C22-5] Enhancement of Thermoelectric Performance of Si Film by Al Ultrathin Layer Deposition

〇(M2C)Anthony Fracasso George¹, Ryoto Yanagisawa¹, Masahiro Nomura^1,2,3 (1.University of Tokyo, IIS, 2.Nanoquine, 3.JST PRESTO)

Keywords:silicon thermoelectrics, ultra-thinfilm, energy harvesting

With increasing public interest in alternative energy sources, research and development groups are seeking thermoelectric (TE) applications with a low environmental load. Since the TE efficiency of bulk Si is quite low, nanoscale modifications are required to increase ZT and thus its potential use in commercial TE devices. However, many modifications rely on expensive lithography techniques which cannot yield an affordable commercialized TE device. This work demonstrates a low-cost method for increasing the ZT value of doped Si membranes over a large area by the deposition of Al thin films on the Si surface. Suspended bridge structures and isolated Si regions were fabricated in an n-doped SOI wafer for thermal conductivity and electrical conductivity measurements respectively. After fabrication, electron-beam evaporation was used to apply ultra-thinfilms onto the entire silicon surface of two sample sets. A third sample set, with no Al, was left as a reference structure. Within the range of typical operating temperature, thermal conductivity measurements were taken by using the micro-time domain thermalreflectance setup and electrical conductivity was measured using a four-probe technique. Al depositied samples show a ~25% decrease in thermal conductivity and with a minimal reduction in electrical conductivity compared to plain doped membranes. This yields a ~33% increase in the σ / κ ratio in both 0.5 nm and 1.0 nm Al deposited membranes at all measured temperatures.