Advanced Center for Laser Science and Spectroscopy, Department of Physics, Hampton University, Hampton, VA 23668, USA.
Nanoscale. 2018 Jul 9;10(26):12472-12479. doi: 10.1039/c8nr04394a.
A two-dimensional heterostructure of WSe2/MoS2 atomic layers has unique piezoelectric characteristics which depend on the number of atomic layers, stacking type and interlayer interaction size. The van der Waals heterostructure of p- and n-type TMDC atomic layers with different work functions forms a type-II staggered gap alignment. The large band offset of the conduction band minimum and the valence band maximum between p-type WSe2 and n-type MoS2 atomic layers leads to large electric polarization and piezoelectricity. The output voltages for a MoS2/WSe2 partial vertical heterostructure with a size of 3.0 nm × 1.5 nm were 0.137 V and 0.183 V under 4% and 8% tensile strains, respectively. The output voltage of an AB-stacking MoS2/WSe2 heterostructure was larger than that of an AA-stacking heterostructure under 4% tensile strain due to the contribution of intrinsic piezoelectricity and symmetric out-of-plane conditions. The AB-stacking has a lower formation energy and better structural stability compared to AA-stacking. The large output voltage of nanoscale partial or full vertical heterostructures of 2D WSe2/MoS2 atomic layers in addition to the increased output voltage through the series connection of multiple nanoscale piezoelectric devices will enable the realization of nano-electromechanical systems (NEMS) with TMDC heterostructure atomic layers.
二维 WSe2/MoS2 原子层异质结构具有独特的压电特性，这些特性取决于原子层数、堆叠类型和层间相互作用大小。具有不同功函数的 p 型和 n 型 TMDC 原子层的范德华异质结构形成了 II 型交错带隙排列。p 型 WSe2 和 n 型 MoS2 原子层之间导带最小值和价带最大值的大能带偏移导致了大的极化和压电性。在 4%和 8%的拉伸应变下，尺寸为 3.0nm×1.5nm 的 MoS2/WSe2 部分垂直异质结构的输出电压分别为 0.137V 和 0.183V。由于内禀压电性和对称的面外条件的贡献，在 4%的拉伸应变下，AB 堆叠的 MoS2/WSe2 异质结构的输出电压大于 AA 堆叠的异质结构。与 AA 堆叠相比，AB 堆叠具有更低的形成能和更好的结构稳定性。2D WSe2/MoS2 原子层纳米级部分或全垂直异质结构的大输出电压，以及通过多个纳米级压电器件的串联来增加输出电压，将使 TMDC 异质结构原子层的纳米机电系统 (NEMS) 的实现成为可能。
