High Strain Engineering of a Suspended WSSe Monolayer Membrane by Indentation and Measured by Tip-Enhanced Photoluminescence

Straintronics involves the manipulation and regulation of the electronic characteristics of 2D materials through the use of macro- and nano-scale strain engineering. In this study, an atomic force microscope (AFM) coupled with an optical system is used to perform indentation measurements and tip-enhanced photoluminescence (TEPL), allowing to extract the local optical response of a suspended monolayer membrane of ternary WSSe at various levels of deformation, up to strains of 10%. The photoluminescence signal is modeled considering the deformation, stress distribution, and strain dependence of the WSSe band structure. An additional TEPL signal is observed that exhibits significant variation under strain, with 64 meV per percent of elongation. This peak is linked to the highly strained 2D material lying right underneath the tip. The amplification of the signal and its relation to the excitonic funneling effect are discussed in a more comprehensive model. The diffusion caused by Auger recombination against the radiative excitonic decay will also be compared. TEPL is used to examine and comprehend the local physics of 2D semi-conducting materials subjected to extreme mechanical strain. Chemical vapor deposition-fabricated 2D ternaries possess high strain resistance, comparable to the benchmark MoS₂, and a high Young's modulus of 273 GPa.