Nanobubbles naturally formed at the interface between 2D materials and their substrate are known to act as exciton recombination centers because of the reduced bandgap due to local strain, which in turn scales with the aspect ratio of the bubbles. The common understanding suggests that the aspect ratio is a universal constant independent of the bubble size. Here, by combining scanning tunneling microscopy and molecular dynamics, we show that the universal aspect ratio breaks down in MoS₂ nanobubbles below a critical radius (≈10 nm), where the aspect ratio increases with increasing size. Accordingly, additional atomic-level analyses indicate that the strain increases from 3% to 6% in the sub-critical size range. Using scanning tunneling spectroscopy, we demonstrate that the bandgap decreases as a function of the size. Thus, tunable quantum emitters can be obtained in 2D semiconductors by controlling the radius of the nanobubbles.

已知在二维材料与其基底之间的界面处自然形成的纳米气泡可充当激子复合中心，因为局部应变导致带隙减小，而局部应变又随气泡的纵横比缩放。人们普遍认为，长宽比是一个与气泡大小无关的通用常数。_{在这里，通过结合扫描隧道显微镜和分子动力学，我们证明了 MoS 2}中普遍的纵横比被打破低于临界半径（约 10 nm）的纳米气泡，其中纵横比随着尺寸的增加而增加。因此，额外的原子级分析表明，在亚临界尺寸范围内，应变从 3% 增加到 6%。使用扫描隧道光谱，我们证明带隙随着尺寸的变化而减小。因此，通过控制纳米气泡的半径，可以在二维半导体中获得可调谐的量子发射器。