Probing the Optical Properties and Strain-Tuning of Ultrathin Mo<sub>1- x</sub>W <sub>x</sub>Te<sub>2</sub>.
basic_science · Level V
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- Record sourced from PubMed, PMID 29561623.
- Also identified by DOI 10.1021/acs.nanolett.8b00049 and PMC identifier 7243468.
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Abstract
Ultrathin transition metal dichalcogenides (TMDCs) have recently been extensively investigated to understand their electronic and optical properties. Here we study ultrathin Mo<sub>0.91</sub>W<sub>0.09</sub>Te<sub>2</sub>, a semiconducting alloy of MoTe<sub>2</sub>, using Raman, photoluminescence (PL), and optical absorption spectroscopy. Mo<sub>0.91</sub>W<sub>0.09</sub>Te<sub>2</sub> 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<sub>2</sub> counterpart. We apply tensile strain, for the first time, to monolayer MoTe<sub>2</sub> and Mo<sub>0.91</sub>W<sub>0.09</sub>Te<sub>2</sub> 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<sub>2</sub> and Mo<sub>0.91</sub>W<sub>0.09</sub>Te<sub>2</sub> extend the range of band gaps of TMDC monolayers further into the near-infrared, an important attribute for potential applications in optoelectronics.