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Sousa FB, Nadas R, Martins R, Barboza APM, Soares JS, Neves BRA, Silvestre I, Jorio A, Malard LM. Disentangling doping and strain effects at defects of grown MoS 2 monolayers with nano-optical spectroscopy. NANOSCALE 2024. [PMID: 38805074 DOI: 10.1039/d4nr00837e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
The role of defects in two-dimensional semiconductors and how they affect the intrinsic properties of these materials have been a widely researched topic over the past few decades. Optical characterization techniques such as photoluminescence and Raman spectroscopies are important tools to probe the physical properties of semiconductors and the impact of defects. However, confocal optical techniques present a spatial resolution limitation lying in a μm-scale, which can be overcome by the use of near-field optical measurements. Here, we use tip-enhanced photoluminescence and Raman spectroscopies to unveil the nanoscale optical properties of grown MoS2 monolayers, revealing that the impact of doping and strain can be disentangled by the combination of both techniques. A noticeable enhancement of the exciton peak intensity corresponding to trion emission quenching is observed at narrow regions down to a width of 47 nm at grain boundaries related to doping effects. Besides, localized strain fields inside the sample lead to non-uniformities in the intensity and energy position of photoluminescence peaks. Finally, two distinct MoS2 samples present different nano-optical responses at their edges associated with opposite strains. The edge of the first sample shows a photoluminescence intensity enhancement and energy blueshift corresponding to a frequency blueshift for E2g and 2LA Raman modes. In contrast, the other sample displays a photoluminescence energy redshift and frequency red shifts for E2g and 2LA Raman modes at their edges. Our work highlights the potential of combining tip-enhanced photoluminescence and Raman spectroscopies to probe localized strain fields and doping effects related to defects in two-dimensional materials.
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Affiliation(s)
- Frederico B Sousa
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
| | - Rafael Nadas
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
- FabNS, Belo Horizonte, Minas Gerais 31310-260, Brazil
| | - Rafael Martins
- Departamento de Física, Universidade Federal de Ouro Preto, Ouro Preto, Minas Gerais 35400-000, Brazil
| | - Ana P M Barboza
- Departamento de Física, Universidade Federal de Ouro Preto, Ouro Preto, Minas Gerais 35400-000, Brazil
| | - Jaqueline S Soares
- Departamento de Física, Universidade Federal de Ouro Preto, Ouro Preto, Minas Gerais 35400-000, Brazil
| | - Bernardo R A Neves
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
| | - Ive Silvestre
- Departamento de Física, Universidade Federal de Ouro Preto, Ouro Preto, Minas Gerais 35400-000, Brazil
| | - Ado Jorio
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
| | - Leandro M Malard
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
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Portes A, Nadas R, Jorio A, Ramirez JC. Electro-optical properties of a graphene device on a tip-enhanced Raman spectroscopy system. OPTICS LETTERS 2024; 49:871-874. [PMID: 38359204 DOI: 10.1364/ol.512195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Accepted: 01/10/2024] [Indexed: 02/17/2024]
Abstract
This paper investigates the impact of graphene on tip-enhanced Raman spectroscopy (TERS) by developing an electromagnetic characterization of the TERS-graphene device system. The study focuses on the interaction between the tip, the gate voltage, and the sample, specifically examining the electromagnetic effects in the system. Employing a finite element method (FEM)-based simulation model, we meticulously dissect the electric field distribution and the Raman amplification when graphene is introduced into the system. Our findings reveal that including graphene results in a marginal reduction in Raman amplification and a negligible variation in the induced charges within the system. To reinforce our simulations, we employ a simplified capacitor model, which corroborates our results, showcasing negligible induced charges and validating the obtained capacitance values. In this manuscript, we also explore the influence of the setup on the electro-optical properties of graphene, revealing a slight variation in conductivity despite strong changes in chemical potential. Overall, this work contributes to understanding TERS's electromagnetic aspects in the presence of graphene.
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de Oliveira R, Cadore AR, Freitas RO, Barcelos ID. Review on infrared nanospectroscopy of natural 2D phyllosilicates. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2023; 40:C157-C168. [PMID: 37132988 DOI: 10.1364/josaa.482518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Phyllosilicates have emerged as a promising class of large bandgap lamellar insulators. Their applications have been explored from the fabrication of graphene-based devices to 2D heterostructures based on transition metal dichalcogenides with enhanced optical and polaritonics properties. In this review, we provide an overview of the use of infrared (IR) scattering-type scanning near-field optical microscopy (s-SNOM) for studying nano-optics and local chemistry of a variety of 2D natural phyllosilicates. Finally, we bring a brief update on applications that combine natural lamellar minerals into multifunctional nanophotonic devices driven by electrical control.
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Peña-Obeso PJ, Huirache-Acuña R, Ramirez-Zavaleta FI, Rivera JL. Stability of Non-Concentric, Multilayer, and Fully Aligned Porous MoS 2 Nanotubes. MEMBRANES 2022; 12:818. [PMID: 36005733 PMCID: PMC9415411 DOI: 10.3390/membranes12080818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2022] [Revised: 08/10/2022] [Accepted: 08/12/2022] [Indexed: 06/15/2023]
Abstract
Nanotubes made of non-concentric and multiple small layers of porous MoS2 contain inner pores suitable for membrane applications. In this study, molecular dynamics simulations using reactive potentials were employed to estimate the stability of the nanotubes and how their stability compares to macroscopic single- (1L) and double-layer MoS2 flakes. The observed stability was explained in terms of several analyses that focused on the size of the area of full-covered layers, number of layers, polytype, and size of the holes in the 1L flakes. The reactive potential used in this work reproduced experimental results that have been previously reported, including the small dependency of the stability on the polytype, the formation of S-S bonds between inter- and intra-planes, and the limit of stability for two concentric rings forming a single ring-like flake.
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Affiliation(s)
- Pablo Jahir Peña-Obeso
- Facultad de Ingeniería Química, Universidad Michoacana de San Nicolás de Hidalgo, Morelia 58000, Mexico
| | - Rafael Huirache-Acuña
- Facultad de Ingeniería Química, Universidad Michoacana de San Nicolás de Hidalgo, Morelia 58000, Mexico
| | | | - José Luis Rivera
- Facultad de Ciencias Físico–Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia 58000, Mexico
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Gadelha AC, Nguyen VH, Neto EGS, Santana F, Raschke MB, Lamparski M, Meunier V, Charlier JC, Jorio A. Electron-Phonon Coupling in a Magic-Angle Twisted-Bilayer Graphene Device from Gate-Dependent Raman Spectroscopy and Atomistic Modeling. NANO LETTERS 2022; 22:6069-6074. [PMID: 35878122 DOI: 10.1021/acs.nanolett.2c00905] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The importance of phonons in the strong correlation phenomena observed in twisted-bilayer graphene (TBG) at the so-called magic-angle is under debate. Here we apply gate-dependent micro-Raman spectroscopy to monitor the G band line width in TBG devices of twist angles θ = 0° (Bernal), ∼1.1° (magic-angle), and ∼7° (large-angle). The results show a broad and p-/n-asymmetric doping behavior at the magic angle, in clear contrast to the behavior observed in twist angles above and below this point. Atomistic modeling reproduces the experimental observations in close connection with the joint density of electronic states in the electron-phonon scattering process, revealing how the unique electronic structure of magic-angle TBGs influences the electron-phonon coupling and, consequently, the G band line width. Overall, the value of the G band line width in magic-angle TBG is larger when compared to that of the other samples, in qualitative agreement with our calculations.
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Affiliation(s)
- Andreij C Gadelha
- Physics Department, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil
- Department of Physics, and JILA, University of Colorado at Boulder, Boulder, Colorado 80309, United States
| | - Viet-Hung Nguyen
- Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain (UCLouvain), Louvain-la-Neuve 1348, Belgium
| | - Eliel G S Neto
- Physics Institute, Universidade Federal da Bahia, Salvador, Bahia 40170-115 Brazil
| | - Fabiano Santana
- Physics Department, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil
| | - Markus B Raschke
- Department of Physics, and JILA, University of Colorado at Boulder, Boulder, Colorado 80309, United States
| | - Michael Lamparski
- Department of Physics, Applied Physics, and Astronomy, Jonsson Rowland Science Center, Troy, New York 12180-3590, United States
| | - Vincent Meunier
- Department of Physics, Applied Physics, and Astronomy, Jonsson Rowland Science Center, Troy, New York 12180-3590, United States
| | - Jean-Christophe Charlier
- Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain (UCLouvain), Louvain-la-Neuve 1348, Belgium
| | - Ado Jorio
- Physics Department, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil
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Malard LM, Lafeta L, Cunha RS, Nadas R, Gadelha A, Cançado LG, Jorio A. Studying 2D materials with advanced Raman spectroscopy: CARS, SRS and TERS. Phys Chem Chem Phys 2021; 23:23428-23444. [PMID: 34651627 DOI: 10.1039/d1cp03240b] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Raman spectroscopy has been established as a valuable tool to study and characterize two-dimensional (2D) systems, but it exhibits two drawbacks: a relatively weak signal response and a limited spatial resolution. Recently, advanced Raman spectroscopy techniques, such as coherent anti-Stokes spectroscopy (CARS), stimulated Raman scattering (SRS) and tip-enhanced Raman spectroscopy (TERS), have been shown to overcome these two limitations. In this article, we review how useful physical information can be retrieved from different 2D materials using these three advanced Raman spectroscopy and imaging techniques, discussing results on graphene, hexagonal boron-nitride, and transition metal di- and mono-chalcogenides, thus providing perspectives for future work in this early-stage field of research, including similar studies on unexplored 2D systems and open questions.
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Affiliation(s)
- Leandro M Malard
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
| | - Lucas Lafeta
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
| | - Renan S Cunha
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
| | - Rafael Nadas
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
| | - Andreij Gadelha
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
| | - Luiz Gustavo Cançado
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
| | - Ado Jorio
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
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