Nanoscale Spectroscopy of Dielectric Properties of Mica

Fali, Alireza; Gamage, Sampath; Howard, Marquez; Folland, Thomas G.; Mahadik, Nadeemullah A.; Tiwald, Thomas E.; Bolotin, Kirill I.; Caldwell, Joshua D.; Abate, Yohannes

doi:10.1021/acsphotonics.0c00951

Cited by 22 publications

(15 citation statements)

References 39 publications

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“…Dark excitons can be visualized using TEPL for TMD samples on metallic substrates because the electric field strength perpendicular to the sample surface is drastically enhanced 12 , 19 . In contrast, the s-SNOM signal for atomically thin TMDs is governed by the in-plane dielectric function 32 , 44 , which arises from bright excitons (see SOM). To experimentally confirm the dominant role of bright excitons in our data, we compared the bright exciton resonance energy obtained from far-field PL spectra on the same sample 45 with the resonance energy in our s-SNOM spectra.…”

Section: Resultsmentioning

confidence: 99%

Nano-spectroscopy of excitons in atomically thin transition metal dichalcogenides

Zhang

Chen

et al. 2022

Nat Commun

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Excitons play a dominant role in the optoelectronic properties of atomically thin van der Waals (vdW) semiconductors. These excitons are amenable to on-demand engineering with diverse control knobs, including dielectric screening, interlayer hybridization, and moiré potentials. However, external stimuli frequently yield heterogeneous excitonic responses at the nano- and meso-scales, making their spatial characterization with conventional diffraction-limited optics a formidable task. Here, we use a scattering-type scanning near-field optical microscope (s-SNOM) to acquire exciton spectra in atomically thin transition metal dichalcogenide microcrystals with previously unattainable 20 nm resolution. Our nano-optical data revealed material- and stacking-dependent exciton spectra of MoSe2, WSe2, and their heterostructures. Furthermore, we extracted the complex dielectric function of these prototypical vdW semiconductors. s-SNOM hyperspectral images uncovered how the dielectric screening modifies excitons at length scales as short as few nanometers. This work paves the way towards understanding and manipulation of excitons in atomically thin layers at the nanoscale.

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Section: Resultsmentioning

confidence: 99%

Nano-spectroscopy of excitons in atomically thin transition metal dichalcogenides

Zhang

Chen

et al. 2022

Nat Commun

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“…To replicate the large near-field amplitudes extracted from the finite element analysis, we choose L = 600 nm as the best value in the FDM. Larger values for L are incompatible with the requirement that L ≪ λ. , With these parameters, we find an optimal value of g = 0.98 e 0.14 i for a doped Si substrate with a dopant concentration in the range of 1 × 10 18 cm –3 to 1 × 10 21 cm –3 .…”

Section: Methodsmentioning

confidence: 79%

Quantitative Local Conductivity Imaging of Semiconductors Using Near-Field Optical Microscopy

et al. 2022

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We demonstrate contactless, nanoscale measurements of local conductivity, free carrier density, and mobility using phase-resolved infrared (IR) scattering-type near-field optical microscopy (s-SNOM). Our approach extracts quantitative conductivity information by combining analytical and finite-element methods to predict the scattered near-field amplitude and phase for specific sample geometries, without relying on bulk mobility assumptions or empirical fitting parameters. We find that the finite-dipole model (FDM) overestimates the expected near-field amplitude and phase in nonplanar or nanostructured materials, so we employ finite-element modeling to choose appropriate corrections to the FDM and account for sample geometry. The model is validated using a silicon calibration sample, and our results return the free carrier concentration expected based on the encoded dopant profile. Mobility and conductivity are also found to be in good agreement with established models for bulk silicon. This work demonstrates the potential of IR s-SNOM to perform quantitative local conductivity measurements, including the separation of free carrier density and electronic mobility, and represents a step toward the goal of quantitative carrier profiling and mobility mapping using s-SNOM.

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“…In order to quantitatively assess the local conductivity modulation of the charge writing process, we performed scattering type canning near-field microscopy (s-SNOM) imaging of the patterned area of the sample. S-SNOM enables imaging local conductivity changes with high-sensitivity and high-spatial resolution, limited only by the sharpness of the probe tip (see "Methods") [36][37][38][39] . The resulting s-SNOM amplitude images shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Reconfigurable hyperbolic polaritonics with correlated oxide metasurfaces

Aghamiri

Fali

et al. 2022

Nat Commun

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Polaritons enable subwavelength confinement and highly anisotropic flows of light over a wide spectral range, holding the promise for applications in modern nanophotonic and optoelectronic devices. However, to fully realize their practical application potential, facile methods enabling nanoscale active control of polaritons are needed. Here, we introduce a hybrid polaritonic-oxide heterostructure platform consisting of van der Waals crystals, such as hexagonal boron nitride (hBN) or alpha-phase molybdenum trioxide (α-MoO3), transferred on nanoscale oxygen vacancy patterns on the surface of prototypical correlated perovskite oxide, samarium nickel oxide, SmNiO3 (SNO). Using a combination of scanning probe microscopy and infrared nanoimaging techniques, we demonstrate nanoscale reconfigurability of complex hyperbolic phonon polaritons patterned at the nanoscale with high resolution. Hydrogenation and temperature modulation allow spatially localized conductivity modulation of SNO nanoscale patterns, enabling robust real-time modulation and nanoscale reconfiguration of hyperbolic polaritons. Our work paves the way towards nanoscale programmable metasurface engineering for reconfigurable nanophotonic applications.

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Nanoscale Spectroscopy of Dielectric Properties of Mica

Cited by 22 publications

References 39 publications

Nano-spectroscopy of excitons in atomically thin transition metal dichalcogenides

Nano-spectroscopy of excitons in atomically thin transition metal dichalcogenides

Quantitative Local Conductivity Imaging of Semiconductors Using Near-Field Optical Microscopy

Reconfigurable hyperbolic polaritonics with correlated oxide metasurfaces

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