Supplementary material
Thermoelectric Figure of Merit Calculations for Semiconducting
Nanowires
Jane E. Cornett1, Oded Rabin1,2†
1
Department of Materials Science and Engineering, University of Maryland, College Park, MD
20742, USA
2
Institute for Research in Electronics and Applied Physics, University of Maryland, College
Park, MD 20742, USA
FIG. S1
FIG. S1. Room temperature thermoelectric figure of merit (ZT) values calculated assuming
radius-dependent lattice thermal conductivity values from Ref. [1].
In order to calculate ZT, the lattice contribution to thermal conductivity is considered. Due to
limited experimental data on the  l of NWs, we utilize values for  l (r ) calculated by Mingo in
Ref. [1,2]. The authors first derive the full phonon dispersion relations assuming a StillingerWeber potential. Then, considering the effects of impurity, Umklapp and diffuse boundary
scattering, the phonon mean free path and lattice thermal conductivity are calculated as a
function of NW radius. Over the radius range 10 < r < 100 nm,  l increases from 0.8 W/m-K to
3.9 W/m-K – well below the bulk value of 18 W/m-K 1. Using this model for  l , calculations of
ZT(r) result in a monotonic decreasing function (Fig. S1). In the limit of large r, the calculated
ZT value approaches 0.03, the ZT of bulk n-type InSb 3. Though the method of Ref. [2] for
calculating  l (r ) has been verified experimentally for silicon NWs, no experimental evidence for
InSb has yet confirmed the validity of this assumed radius-dependence.
REFERENCES
1
2
3
N. Mingo and D. A. Broido, Phys. Rev. Lett. 93 (24), 246106 (2004).
N. Mingo, Phys. Rev. B 68 (11), 113308 (2003).
Shigeo Yamaguchi, Takayuki Matsumoto, Jun Yamazaki, Nakaba Kaiwa, and Atsushi
Yamamoto, Appl. Phys. Lett. 87 (20), 201902 (2005).