Tuning the Photoluminescence of Few-Layer MoS₂ Nanosheets by Mechanical Nanostamping for Broadband Optoelectronic Applications

Tuning the optical signature of two-dimensional (2D) materials through local strain is an exciting avenue for advanced optoelectronic device engineering. Here, we demonstrate a controllable way to locally tune the energy of photoluminescent emission of few-layer MoS2 while enhancing their PL intensity using a mechanical nanostamping technique. In this method, regions of tensile and compressive strain are simultaneously attained through mechanically nanostamped arrays on a Si substrate. We demonstrated that the band gap and lattice constant of exfoliated MoS2 layers are locally modified in such a nonzero Gaussian curvature through photoluminescence (PL) and Raman spectroscopy characterization. Moreover, within the high strain regions, relative to the nanoindent center, an enhanced direct band gap emission of 5–7L was blue-shifted (tensile strain) and red-shifted (compressive strain) in the order of 45 ± 5 and 37 ± 3 meV, respectively. Multiscale simulations help explain the mechanism of strain-induced electronic band structure modification from a macroscopic scale to atomic scale. The straightforward fabrication procedure presented here can open a pathway to strain engineer 2D semiconductors for future optoelectronic device applications.