Revealing Strain and Disorder in Transition-Metal Dichalcogenides Using Hyperspectral Photoluminescence Imaging

Abstract

Hyperspectral photoluminescence (HSPL) imaging provides spatially resolved spectral information for monolayer transition-metal dichalcogenides (TMDs), enabling the detection of subtle variations in excitonic features that are not accessible with conventional optical or photoluminescence intensity imaging. We employ HSPL to map the microscopic spatial distribution of strain and disorder in hBN-encapsulated MoSe$_2$ and WSe$_2$ samples. Quantitative extraction of exciton, trion, and biexciton energies and linewidths reveals strain gradients and localized deformations, such as wrinkles and ripples. The technique allows for characterization of regions with uniform optical properties and identification of areas affected by micro-scale disorder, which may be missed by optical microscopy. Measurements on samples with different device architectures and fabrication processes demonstrate the general utility of hyperspectral PL imaging for assessing spatial heterogeneity and optoelectronic quality in two-dimensional materials.

Figures (6)

• Figure 1: a, Diagram of heterostructure labeled as Sample-1, consisting of an hBN encapsulated MoSe2 monolayer. b, Microscope image of the heterostructure. c, Spatial map of the total PL intensity from the MoSe2 at a temperature of 6 K. The spectrum at the location marked by the white box is shown in Fig. \ref{['fig:figure2']}.
• Figure 2: Quantitative parameter extraction. Spectrum from a single location marked by white box in Fig. \ref{['fig:figure1']}c, with trion (red) and exciton (blue) polynomial fits.
• Figure 3: a, Spatial map of the center energy of the exciton resonance with dashed lines indicating the linecuts shown in b, Horizontal linecut. c, Vertical linecut.
• Figure 4: Left: Spatial map of the Trion fit center energy. Right: Map of Trion binding energy, highlighting the contrast between homogeneous regions and regions with wrinkles/ripples indicative of local strain and disorder.
• Figure 5: a, Exciton FWHM map with white letters indicating the locations of the spectra in panels b–d. b, Exciton spectrum from a central region with a red-shifted resonance. c, a blue-shifted edge region. d, a location with a pronounced wrinkle.