Tuning the photoluminescence of few-layer MoS₂nanosheets 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 fewlayer 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 redshifted (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.