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SEM-Micrograph of Molybdenum Disulfide (MoS<sub>2</sub>) Single-Layers
SEM-Micrograph of Molybdenum Disulfide (MoS2) Single-Layers
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The number of microstructural information that are contained in a micrograph obtained by a microscopic investigation technique like Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), etc. depends on the image quality and more precisely on its sharpness, brightness and contrast. In the case of SEM, a micrograph is adequately contrasted and therefore rich of details, greater is the number of electrons emitted from the sample surface during the observation and collected by the detector. Under the same kinetic energy of the incident beam (primary electrons, PE) and therefore for the same depth of penetration of the electron beam into the sample surface, the number of emitted secondary electrons (SE) depends on the inclination of the beam with respect to the surface plane. Indeed, a rather inclined PE-beam (for example, an oblique PE-beam, i.e. almost parallel to the surface) causes SE emission from regions very close to the surface (the closer, the more inclined it is), while a PE-beam perpendicular to the surface plane causes emission of SE from deeper regions. Since SE have very low kinetic energy values (less than 10keV), they are able to leave the sample and reach the detector (located in the high-vacuum SEM chamber) only in the case they are generated in regions very close to the surface; differently, they are completely absorbed by the interaction with matter. Therefore, to obtain high SE emission, the sample must be tilted with respect to the horizontal position. High tilting values can be achieved much easily if the surface to be observed is first vertically positioned (inclination of 90°) and then inclination is slightly reduced by using the instrumental tilting control (manual tilting) up to achieve a well-focused observation field. Such focusing is facilitated by the high field depth, characterizing the SEM technique. In order to place the sample in a vertical position, it is necessary to use an adequate specimen holder. The here presented approach is essential in the study of 2D-nanostructures because of low contrast generally characterizing the SEM observation of objects with nanometric height.

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Update Date:
24 Feb 2025
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Keywords
2D-NanostructuresMolybdenum disulfideSEMTiltingOblique observationSingle-layer
Carotenuto, G.; Nicolais, F. SEM-Micrograph of Molybdenum Disulfide (MoS2) Single-Layers. Encyclopedia. Available online: https://encyclopedia.pub/image/2963 (accessed on 18 April 2025).
Carotenuto G, Nicolais F. SEM-Micrograph of Molybdenum Disulfide (MoS2) Single-Layers. Encyclopedia. https://encyclopedia.pub/image/2963. Published Feb 05, 2025. Accessed 18 April, 2025.
Carotenuto, Gianfranco, Francesca Nicolais. SEM-Micrograph of Molybdenum Disulfide (MoS2) Single-Layers. 2025. Encyclopedia. https://encyclopedia.pub/image/2963.
Carotenuto, G., & Nicolais, F. (2025). SEM-Micrograph of Molybdenum Disulfide (MoS2) Single-Layers. Encyclopedia. https://encyclopedia.pub/image/2963
Carotenuto, Gianfranco and Francesca Nicolais. "SEM-Micrograph of Molybdenum Disulfide (MoS2) Single-Layers." Encyclopedia, 2025, https://encyclopedia.pub/image/2963. Accessed 18 April, 2025.
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