1–xW_xTe₂]]>

摘要

Ultrathin transition metal dichalcogenides (TMDCs) have recently been extensively investigated to understand their electronic and optical properties. Here we study ultrathin Mo_(0.91)W_(0.09)Te_(2), a semiconducting alloy of MoTe_(2), using Raman, photoluminescence (PL), and optical absorption spectroscopy. Mo_(0.91)W_(0.09)Te_(2) transitions from an indirect to a direct optical band gap in the limit of monolayer thickness, exhibiting an optical gap of 1.10 eV, very close to its MoTe_(2) counterpart. We apply tensile strain, for the first time, to monolayer MoTe_(2) and Mo_(0.91)W_(0.09)Te_(2) to tune the band structure of these materials; we observe that their optical band gaps decrease by 70 meV at 2.3% uniaxial strain. The spectral widths of the PL peaks decrease with increasing strain, which we attribute to weaker exciton–phonon intervalley scattering. Strained MoTe_(2) and Mo_(0.91)W_(0.09)Te_(2) extend the range of band gaps of TMDC monolayers further into the near-infrared, an important attribute for potential applications in optoelectronics.