Abstract
The thermal conductivity of silicon/germanium nanowires with different geometry and composition has beenstudied by using the nonequilibrium molecular dynamics method. The thermal conductivity of the Si1-xGexnanowire is shown to firstly decrease, reaches a minimum at x=0.4 and then to increase, as the germaniumcontent x grows. It was found that in the tubular Si nanowires the thermal conductivity decreases monotonouslywith increasing radius of the cylindrical void. The phonon spectra were calculated and the mechanisms of phononscattering in the investigated nanowires were analyzed.
Highlights
Semiconducting silicon nanowires have attracted a great attention in recent years because of their excellent electrical and mechanical properties and the potential applications in many areas including solar cells [1], field effect transistors [2], lithium-ion batteries [3]
We explore how the combination of Ge content and geometry modification may be used to reduce the conductivity of Si/Ge nanowires at room temperature
The initial Si nanowire is constructed from diamond-structured bulk silicon with 12 unit cells in the diameter DNW, and 100 unit cells in the longitudinal direction which corresponds to a cross section area of 33.3 nm2 and a length of L = 54.3 nm
Summary
Semiconducting silicon nanowires have attracted a great attention in recent years because of their excellent electrical and mechanical properties and the potential applications in many areas including solar cells [1], field effect transistors [2], lithium-ion batteries [3]. Lowering thermal conductivity without reducing electrical conductivity is desirable to improve the efficiency of thermoelectric energy conversion. Si nanowires can usually be used to enhance the thermoelectric properties of other materials by lowering thermal conductivity. Many approaches have been proposed to further reduce thermal conductivity of nanowires for optimizing thermoelectric performance, such as the introduction of impurity scattering, holey structure, and surface roughness [9,10,11]. Various nanostructuring pathways are proposed to construct diverse nanowires, such as superlattice nanowires [12] core–shell nanowires [13] porous nanowires [14] and kinked structure [15] Another possible way to achieve this is a compound [16].
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