Excitonic Lifetime in CVD-Grown, Few-Layer MoTe₂

Two-dimensional semiconductors such as transition metal dichalcogenides (TMDCs) with high binding energy excitons provide an ideal platform to study exciton phyics such as exciton-exciton annihilation and chemical defect scattering. The dominant exciton decay mechanisms of chemical vapor deposition (CVD) grown, few-layer MoTe₂ are investigated by measuring and statistically analyzing its ultrafast, optical transient reflectivity dynamics under different pump excitation energies, fluences and temperatures. Defect interaction controls the ultrafast exciton decay pathways. Weak intralayer bonding in few-layer, CVD MoTe₂ causes it to have a greater defect density than in other mechanically exfoliated 2D transition metal dichalcogenides. Direct charge carrier occupation of trap states is thought to cause an additional transient feature on the A’ exciton which is not present in the absorption spectrum. Additionally, long-term ambient air exposure does not significantly affect few-layer MoTe₂ exciton decay time and absorption peak shape, increasing this material’s suitability for many technological applications.