Jena Nityasagar, De Sarkar Abir
Institute of Nano Science and Technology, Phase 10, Sector 64, Mohali, Punjab-160 062, India.
J Phys Condens Matter. 2017 Jun 7;29(22):225501. doi: 10.1088/1361-648X/aa6cbc.
Strain and temperature induced tunability in the thermoelectric properties in monolayer MoS (ML-MoS) has been demonstrated using density functional theory coupled to semi-classical Boltzmann transport theory. Compressive strain, in general and uniaxial compressive strain (along the zig-zag direction), in particular, is found to be most effective in enhancing the thermoelectric power factor, owing to the higher electronic mobility and its sensitivity to lattice compression along this direction. Variation in the Seebeck coefficient and electronic band gap with strain is found to follow the Goldsmid-Sharp relation. n-type doping is found to raise the relaxation time-scaled thermoelectric power factor higher than p-type doping and this divide widens with increasing temperature. The relaxation time-scaled thermoelectric power factor in optimally n-doped ML-MoS is found to undergo maximal enhancement under the application of 3% uniaxial compressive strain along the zig-zag direction, when both the (direct) electronic band gap and the Seebeck coefficient reach their maximum, while the electron mobility drops down drastically from 73.08 to 44.15 cm V s. Such strain sensitive thermoelectric responses in ML-MoS could open doorways for a variety of applications in emerging areas in 2D-thermoelectrics, such as on-chip thermoelectric power generation and waste thermal energy harvesting.
利用密度泛函理论结合半经典玻尔兹曼输运理论，已证明单层二硫化钼（ML-MoS）中应变和温度对热电性能的可调性。一般而言，压缩应变，特别是单轴压缩应变（沿锯齿形方向），由于较高的电子迁移率及其对该方向晶格压缩的敏感性，被发现对提高热电功率因子最为有效。发现塞贝克系数和电子带隙随应变的变化遵循戈德史密斯-夏普关系。发现n型掺杂比p型掺杂能使弛豫时间尺度热电功率因子更高，且这种差异随温度升高而增大。当（直接）电子带隙和塞贝克系数都达到最大值时，发现最佳n掺杂的ML-MoS在沿锯齿形方向施加3%单轴压缩应变的情况下，弛豫时间尺度热电功率因子会经历最大增强，而电子迁移率则从73.08急剧下降到44.15 cm² V⁻¹ s⁻¹。ML-MoS中这种对应变敏感的热电响应可为二维热电学新兴领域的各种应用打开大门，例如片上热电发电和废热收集。
