MoS₂ single layers are valued for their sizeable direct bandgap at the heart of the envisaged electronic and optoelectronic applications. Here we experimentally demonstrate that moderate strain values (~2%) can already trigger an indirect bandgap transition and induce a finite charge carrier density in 2D MoS₂ layers. A conclusive proof of the direct-to-indirect bandgap transition is provided by directly comparing the electronic and optical bandgaps of strained MoS₂ single layers obtained from tunneling spectroscopy and photoluminescence measurements of MoS₂ nanobubbles. Upon 2% biaxial tensile strain, the electronic gap becomes significantly smaller (1.45 ± 0.15 eV) than the optical direct gap (1.73 ± 0.1 eV), clearly evidencing a strain-induced direct to indirect bandgap transition. Moreover, the Fermi level can shift inside the conduction band already in moderately strained (~2%) MoS₂ single layers conferring them a metallic character.

MoS ₂单层以其可观的直接带隙而受到重视，这是设想的电子和光电应用的核心。在这里，我们通过实验证明，适度的应变值（〜2％）已经可以触发间接的带隙跃迁，并在2D MoS ₂层中引起有限的载流子密度。通过直接比较由隧道光谱法和MoS _2的光致发光测量获得的应变MoS ₂单层的电子和光学带隙，可以提供直接到间接带隙跃迁的结论性证据。纳米气泡。在2％的双轴拉伸应变下，电子间隙变得比光学直接间隙（1.73±0.1 eV）小得多（1.45±0.15 eV），清楚地证明了应变引起的直接带隙到间接带隙跃迁。此外，费米能级可以在已经处于中等应变（〜2％）的MoS ₂单层中的导带内移动，从而赋予它们金属特性。