Monolayer-to-Mesoscale Modulation of the Optical Properties in 2D CrI3 Mapped by Hyperspectral Microscopy

M. Galbiati; F. Ramiro-Manzano; J. J. Pérez Grau; F. Cantos-Prieto; J. Meseguer-Sánchez; I. Kosic; F. Mione; A. Pallarés Vilar; A. Cantarero; D. Soriano; E. Navarro-Moratalla

doi:10.1103/PhysRevLett.130.176901

Research · Publication & note

Monolayer-to-Mesoscale Modulation of the Optical Properties in 2D CrI3 Mapped by Hyperspectral Microscopy

Research article

M. Galbiati, F. Ramiro-Manzano, J. J. Pérez Grau, F. Cantos-Prieto, J. Meseguer-Sánchez, I. Kosic, F. Mione, A. Pallarés Vilar, A. Cantarero, D. Soriano and E. Navarro-Moratalla

Physical Review Letters 130, 176901 (2023) · Published 27 April 2023

Article summary

Hyperspectral microscopy maps the optical response of two-dimensional CrI3 from the monolayer to mesoscopic thicknesses, revealing few-layer, multilayer and bulk-like regimes.

Reference

M. Galbiati et al., “Monolayer-to-Mesoscale Modulation of the Optical Properties in 2D CrI3 Mapped by Hyperspectral Microscopy,” Phys. Rev. Lett. 130, 176901 (2023). https://doi.org/10.1103/PhysRevLett.130.176901

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Figures

Complete Figure 1 composition from the CrI3 hyperspectral microscopy article — **Figure 1.** Spectroscopic characterization of CrI₃. (a) Visible range transmittance spectra of CrI₃ crystals with a different number of layers. Red curves correspond to thin layers (from 1 to 13 L), blue curves to layers ranging from 14 to ∼100 L, and green curves correspond to bulk (up to 164 L). (b) Polarized Raman scattering of CrI₃ crystals with thicknesses in the few-layer (7 L), multilayer (30 L), and bulk (135 L) ranges. Red and blue curves have been taken with a 45° shift in the polarization angle with respect to the crystallographic axis. The small spectral shift of about 2 cm⁻¹ confirms that the stacking order is monoclinic.

Complete Figure 2 composition from the CrI3 hyperspectral microscopy article — **Figure 2.** Evolution of the dielectric functions in CrI₃ as a function of the layer number. The calculated real (ε₁) and imaginary (ε₂) parts of ε̃ are represented by color maps [(a),(b)] and line plots [(c),(d)], respectively.

Complete Figure 3 composition from the CrI3 hyperspectral microscopy article — **Figure 3.** Identification of different thickness regimes in CrI₃. The few-layer, multilayer, and bulk thickness regimes are depicted according to (a) the layer dependence of ε₁ and ε₂ at 2.66 eV from the fitting process to the dataset shown in Fig. 1; (b) the low- (bottom) and high- (top) energy transmittance minima experimentally measured in the spectra of the dataset shown in Fig. 1, and additional ones, demonstrating the good reproducibility of the results (see Supplemental Material [24] Sec. 2.3). Dotted lines are guides to the eye. (c) Spatially resolved wide-field image of the high-energy transmittance dip position calculated from hyperspectral images of CrI₃ flakes.

Complete Figure 4 composition from the CrI3 hyperspectral microscopy article — **Figure 4.** Theory calculations of the layer-dependent electronic and optical properties of CrI₃. (a),(b) Evolution of ε₁ and ε₂ of CrI₃ with an increasing number of layers calculated in the z direction perpendicular to the layers. (c) Projected band structure and DOS of monolayer CrI₃. Filled and empty circles represent I p orbitals and Cr d orbitals, respectively. The size of the circles is the weight of the orbital wave function in each band. Red and blue stand for spin up and down, respectively. The yellow arrow shows the most probable transition responsible for the low-energy peak in the dielectric function. (d) Evolution of the low-energy peak of ε₂ with an increasing number of layers.