Piezoelectricity in WSe₂/MoS₂ heterostructure atomic layers

Abstract

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.

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“…The other is from the heterointerface polar asymmetry, which is ubiquitous among heterostructures to trigger pyroelectricity and piezoelectricity. [ 40–45 ] The resulting piezopotential is maintained as long as the film is deformed, lending to the constant upward band bending at the interface, as shown in Figure 7b. Upon the light exposure, the photon‐excited electrons are separated and migrate across the ZnO/2D α‐C:H interface, leading to a substantially increased electron density within the ZnO film.…”

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“…First principles calculations showed that the output voltage for an AB-stacked WSe 2 /MoS 2 structure with an overlap area of 3.0 nm × 1.5 nm reaches 0.137 and 0.183 eV under tensile strains of 4% and 8%, respectively. [290] TMDCs can also exhibit triboelectric behavior, with the triboelectric ordering of TMDCs predicted as (−) MoS 2 , MoSe 2 , WS 2 (+). A triboelectric nanogenerator (TENG) can be fabricated using a MoS 2 -nylon pair covered with Cu foils as electrodes.…”

“…First principles calculations showed that the output voltage for an AB‐stacked WSe 2 /MoS 2 structure with an overlap area of 3.0 nm × 1.5 nm reaches 0.137 and 0.183 eV under tensile strains of 4% and 8%, respectively. [ 290 ]…”

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“…Between p- and n-type atomic layers, the large band offset of conduction band minimum (CBM) and valence band maximum (VBM) causes strong electric polarisation and piezoelectric conversion. The piezoelectric characteristics of the MoS 2 /WSe 2 heterostructure were explored by first-principle calculations using density functional theory (DFT), by Felix Jaetae Seo group in 2018 ( Yu et al., 2018 ) as shown in Figures 4 A–4D. Among the pairings of transition metal ions (Mo and W) with dichalcogenides (SE and S), the MoS 2 /WSe 2 heterostructure has the highest band offset between CBM and VBM.…”

“… (C) The distribution of electrostatic potential near the electrode. (D) Variation in output voltage as a function of strain( Yu et al., 2018 ) …”