Imaging of Strain-Modulated Exciton Funneling and Exciton Lifetime Modulation in Multilayer GaSe

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Abstract
Spatially varying strain provides a route to control exciton transport and localization in two-dimensional semiconductors, but resolving these processes requires correlated spatial, spectral, and temporal measurements. Here, we investigate multilayer GaSe suspended over nanopillar arrays using photoluminescence spectroscopy, Raman mapping, and wavelength-resolved fluorescence lifetime imaging microscopy (FLIM). Raman mapping confirms localized tensile strain around the nanopillars, while FLIM reveals complementary emission patterns: free-exciton emission at 615–625 nm forms annular distributions around the pillars, whereas red-shifted strain-localized emission at 630–670 nm is concentrated toward the highly strained pillar regions. For GaSe on Al2O3-coated nanopillars, the strain-localized emission exhibits biexponential decay with characteristic lifetimes near 1.20 and 1.46 ns, together with an increase in the slow lifetime toward the pillar apex and a slow-to-fast amplitude ratio of 7.68. In contrast, the corresponding red-shifted emission on metallic Cu nanopillars is predominantly single exponential, highlighting the influence of the local interface on exciton recombination. The combined spatial redistribution, strain-correlated spectral redshift, and systematic lifetime evolution support strain-guided exciton funneling in multilayer GaSe. These results establish wavelength-resolved FLIM as an effective approach for mapping strain-dependent exciton dynamics and demonstrate nanopillar-induced strain as a means to engineer exciton localization in layered semiconductors.
Funding Information
  • Department of Energy National Nuclear Security Administration Laboratory Residency Graduate Fellowship (DE-NA0004114)
  • National Science Foundation (NSF) (2128367)

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