Directionally-Resolved Phononic Properties of Monolayer 2D Molybdenum Ditelluride (MoTe₂) under Uniaxial Elastic Strain

Understanding the phonon characteristics of two-dimensional (2D) molybdenum ditelluride (MoTe₂) under strain is critical to manipulating its multiphysical properties. Although there have been numerous computational efforts to elucidate the strain-coupled phonon properties of monolayer MoTe₂, empirical validation is still lacking. In this work, monolayer 1H-MoTe₂ under uniaxial strain is studied via in situ micro-Raman spectroscopy. Directionally dependent monotonic softening of the doubly degenerate in-plane E_2g¹ phonon mode is observed with increasing uniaxial strain, where the E_2g¹ peak red-shifts -1.66 ± 0.04 cm^-1/% along the armchair direction and -0.80 ± 0.07 cm^-1/% along the zigzag direction. The corresponding Grüneisen parameters are calculated to be 1.09 and 0.52 along the armchair and zigzag directions, respectively. This work provides the first empirical quantification and validation of the orientation-dependent strain-coupled phonon response in monolayer 1H-MoTe₂ and serves as a benchmark for other prototypical 2D transition-metal tellurides.