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243 results on '"Milekhin, A. G."'

1. Engineering whispering gallery modes in MoSe$_2$/WS$_2$ double heterostructure nanocavities: Towards developing all-TMDC light sources

Author

Alekseev, P. A., Milekhin, I. A., Gasnikova, K. A., Eliseyev, I. A., Davydov, V. Yu., Bogdanov, A. A., Kravtsov, V., Mikhin, A. O., Borodin, B. R., and Milekhin, A. G.

Subjects
Physics - Optics, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Transition metal dichalcogenides (TMDCs) have emerged as highly promising materials for nanophotonics and optoelectronics due to their exceptionally high refractive indices, strong excitonic photoluminescence (PL) in monolayer configurations, and the versatility to engineer van der Waals (vdW) heterostructures. In this work, we exploit the intense excitonic PL of a MoSe$_2$ monolayer combined with the high refractive index of bulk WS$_2$ to fabricate microdisk cavities with tunable light emission characteristics. These microdisks are created from a 50-nm-thick WS$_2$/MoSe$_2$/WS$_2$ double heterostructure using frictional mechanical scanning probe lithography. The resulting cavities achieve a 4-10-fold enhancement in excitonic PL from the MoSe$_2$ monolayer at wavelengths near 800 nm. The excitonic PL peak is modulated by sharp spectral features, which correspond to whispering gallery modes (WGMs) supported by the cavity. A microdisk with a diameter of 2.35 $\mu$m demonstrates WGMs with a quality factor of up to 700, significantly surpassing theoretical predictions and suggesting strong potential for lasing applications. The spectral positions of the WGMs can be finely tuned by adjusting the microdisk's diameter and thickness, as confirmed by theoretical calculations. This approach offers a novel route for developing ultra-compact, all-TMDC double heterostructure light sources with record-small size.

Published
2024

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Author

Ponomarev, S. A., Zakhozhev, K. E., Rogilo, D. I., Kurus’, N. N., Sheglov, D. V., Milekhin, A. G., and Latyshev, A. V.

Published
2022
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16. Resonant plasmon enhancement of light emission from CdSe/CdS nanoplatelets on Au nanodisk arrays.

Author

Milekhin, I. A., Anikin, K. V., Rahaman, M., Rodyakina, E. E., Duda, T. A., Saidzhonov, B. M., Vasiliev, R. B., Dzhagan, V. M., Milekhin, A. G., Batsanov, S. A., Gutakovskii, A. K., Latyshev, A. V., and Zahn, D. R. T.

Subjects
SURFACE enhanced Raman effect, NANOPARTICLES, SURFACE plasmon resonance, ELECTRON beam lithography, RAMAN scattering, OPTICAL properties
Abstract

Semiconducting nanoplatelets (NPLs) have attracted great attention due to the superior photophysical properties compared to their quantum dot analogs. Understanding and tuning the optical and electronic properties of NPLs in a plasmonic environment is a new paradigm in the field of optoelectronics. Here, we report on the resonant plasmon enhancement of light emission including Raman scattering and photoluminescence from colloidal CdSe/CdS nanoplatelets deposited on arrays of Au nanodisks fabricated by electron beam lithography. The localized surface plasmon resonance (LSPR) of the Au nanodisk arrays can be tuned by varying the diameter of the disks. In the case of surface-enhanced Raman scattering (SERS), the Raman intensity profile follows a symmetric Gaussian shape matching the LSPR of the Au nanodisk arrays. The surface-enhanced photoluminescence (SEPL) profile of NPLs, however, follows an asymmetric Gaussian distribution highlighting a compromise between the excitation and emission enhancement mechanisms originating from energy transfer and Purcell effects. The SERS and SEPL enhancement factors depend on the nanodisk size and reach maximal values at 75 and 7, respectively, for the sizes, for which the LSPR energy of Au nanodisks coincides with interband transition energies in the semiconductor platelets. Finally, to explain the origin of the resonant enhancement behavior of SERS and SEPL, we apply a numerical simulation to calculate plasmon energies in Au nanodisk arrays and emission spectra from NPLs in such a plasmonic environment. [ABSTRACT FROM AUTHOR]

Published
2020
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39. Surface- and Tip-Enhanced Raman Scattering by CdSe Nanocrystals on Plasmonic Substrates.

Author

Milekhin, Ilya A., Milekhin, Alexander G., and Zahn, Dietrich R. T.

Subjects
*RAMAN scattering, *SURFACE plasmon resonance, *SERS spectroscopy, *PLASMONICS, *NANOCRYSTALS, *LIGHT scattering, *ATOMIC force microscopy
Abstract

This work presents an overview of the latest results and new data on the optical response from spherical CdSe nanocrystals (NCs) obtained using surface-enhanced Raman scattering (SERS) and tip-enhanced Raman scattering (TERS). SERS is based on the enhancement of the phonon response from nanoobjects such as molecules or inorganic nanostructures placed on metal nanostructured substrates with a localized surface plasmon resonance (LSPR). A drastic SERS enhancement for optical phonons in semiconductor nanostructures can be achieved by a proper choice of the plasmonic substrate, for which the LSPR energy coincides with the laser excitation energy. The resonant enhancement of the optical response makes it possible to detect mono- and submonolayer coatings of CdSe NCs. The combination of Raman scattering with atomic force microscopy (AFM) using a metallized probe represents the basis of TERS from semiconductor nanostructures and makes it possible to investigate their phonon properties with nanoscale spatial resolution. Gap-mode TERS provides further enhancement of Raman scattering by optical phonon modes of CdSe NCs with nanometer spatial resolution due to the highly localized electric field in the gap between the metal AFM tip and a plasmonic substrate and opens new pathways for the optical characterization of single semiconductor nanostructures and for revealing details of their phonon spectrum at the nanometer scale. [ABSTRACT FROM AUTHOR]

Published
2022
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48. Morphology-induced phonon spectra of CdSe/CdS nanoplatelets: core/shell vs. core–crown

Author

Dzhagan, V., Milekhin, A. G., Valakh, M. Ya., Pedetti, S., Tessier, M., Dubertret, B., and Zahn, D. R. T.

Subjects
Condensed Matter::Materials Science, Phonon, nanostrukture, optical spectroscopy, Raman scattering, ddc:530, Phonon, Nanostruktur, Optische Spektroskopie, Raman-Effekt, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Phonon, Nanostruktur, Optische Spektroskopie, Raman-Streuung
Abstract

Recently developed two-dimensional colloidal semiconductor nanocrystals, or nanoplatelets (NPLs), extend the palette of solution-processable free-standing 2D nanomaterials of high performance. Growing CdSe and CdS parts subsequently in either side-by-side or stacked manner results in core–crown or core/shell structures, respectively. Both kinds of heterogeneous NPLs find efficient applications and represent interesting materials to study the electronic and lattice excitations and interaction between them under strong one-directional confinement. Here, we investigated by Raman and infrared spectroscopy the phonon spectra and electron–phonon coupling in CdSe/CdS core/shell and core–crown NPLs. A number of distinct spectral features of the two NPL morphologies are observed, which are further modified by tuning the laser excitation energy Eexc between in- and off-resonant conditions. The general difference is the larger number of phonon modes in core/shell NPLs and their spectral shifts with increasing shell thickness, as well as with Eexc. This behaviour is explained by strong mutual influence of the core and shell and formation of combined phonon modes. In the core–crown structure, the CdSe and CdS modes preserve more independent behaviour with only interface modes forming the phonon overtones with phonons of the core. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Published
2017

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