Ultralow Thermal Conductivity Minimum in Silicon Supercrystals with Weakly and Strongly Bonded Germanium Nanodots for Thermoelectrics

作者：Gillet Jean Numa^*

来源：ACS Sustainable Chemistry & Engineering, 2013, 1(6): 611-618.

DOI：10.1021/sc400020c

• Molecular modeling
• Green energy materials
• Nanomaterials
• Thermoelectrics
• Alternative energy

An ultralow thermal conductivity, showing a minimum of the order of 0.01 W/(m K) is predicted at T = 300 K in a Si/Ge quantum dot crystal with a Ge nanodot spacing d = +/- 30 nm. This theoretical result is obtained when all Ge nanodot interfaces are assumed to be weakly bonded with respect to the Si matrix. The thermal conductivity is a decreasing functional of the weakly bonded nanodot density q, defined as the number of weakly bonded dots divided by the total number of dots in the Si/Ge supercrystal. The thermal conductivity minimum for a given q is reached when d is increased to the optimal period d*. When only one nanodot out of six is weakly bonded (case of q = 1/6), the thermal conductivity of air (+/- 0.025 W/(m K)) is already reached. A high thermoelectric figure of merit ZT is envisioned. Indeed, ZT depends on the inverse of the thermal conductivity, which may present +/- 15 000-fold reduction compared with that of bulk Si (case of q = 1). The +/- 1 W/(m K) mark could not be significantly beaten using nanomaterials with phonon blocking properties presenting a low dimensionality than 3, in contrast to the supercrystal weak bonds.

• 出版日期2013-6