Raman scattering is a powerful inelastic light scattering technique able to probe the vibrational properties of materials. This technique has been successfully employed in semiconductor nanowires to provide information on their fundamental properties, such as the phononic properties, the crystal composition, and the electronic band structure. When performed in a polarization-resolved manner on a single nanowire, Raman spectroscopy can even allow addressing the nanowire’s crystal structure. This is a fact of pivotal importance, as crystal phase is emerging as a novel degree of freedom in the bandgap engineering and phonon engineering of materials, and the control of the crystal phase is a possibility uniquely offered by nanowires. Indeed, recent advances in the synthetic growth of nanowires have given access to crystal phases (e.g., hexagonal phase in Si and Ge) that in the bulk can only be obtained under extreme pressure conditions, and it is possible to controllably switch between different crystal phases during the growth of nanowires. The realization and, even more, the interpretation of polarized Raman experiments on nanowires can be non-trivial, as several issues have to be considered. Therefore, in this chapter, we provide the basic theoretical background necessary to calculate Raman selection rules and interpret polarization-resolved Raman spectra of semiconductor nanowires. We also discuss the main ingredients of a Raman setup, with a focus on the scattering geometries typically used for nanowires. We highlight the main differences in the Raman spectra of nanowires with cubic and hexagonal crystal symmetries, and we treat also the case of the most challenging type of heterostructure: a nanoscale crystal-phase homostructure. Finally, we discuss resonant Raman experiments that allow the determination of the energy of some electronic transitions in nanowires. We focus mostly on a very new material system, namely Ge nanowires with controlled crystal phase, but the general procedure that we establish can be applied to several types of nanostructures.

Addressing Crystal Structure in Semiconductor Nanowires by Polarized Raman Spectroscopy / Fasolato, Claudia; Zardo, Ilaria; De Luca, Marta. - (2021), pp. 307-348. [10.1007/978-981-15-9050-4_7].

Addressing Crystal Structure in Semiconductor Nanowires by Polarized Raman Spectroscopy

Fasolato, Claudia;De Luca, Marta
2021

Abstract

Raman scattering is a powerful inelastic light scattering technique able to probe the vibrational properties of materials. This technique has been successfully employed in semiconductor nanowires to provide information on their fundamental properties, such as the phononic properties, the crystal composition, and the electronic band structure. When performed in a polarization-resolved manner on a single nanowire, Raman spectroscopy can even allow addressing the nanowire’s crystal structure. This is a fact of pivotal importance, as crystal phase is emerging as a novel degree of freedom in the bandgap engineering and phonon engineering of materials, and the control of the crystal phase is a possibility uniquely offered by nanowires. Indeed, recent advances in the synthetic growth of nanowires have given access to crystal phases (e.g., hexagonal phase in Si and Ge) that in the bulk can only be obtained under extreme pressure conditions, and it is possible to controllably switch between different crystal phases during the growth of nanowires. The realization and, even more, the interpretation of polarized Raman experiments on nanowires can be non-trivial, as several issues have to be considered. Therefore, in this chapter, we provide the basic theoretical background necessary to calculate Raman selection rules and interpret polarization-resolved Raman spectra of semiconductor nanowires. We also discuss the main ingredients of a Raman setup, with a focus on the scattering geometries typically used for nanowires. We highlight the main differences in the Raman spectra of nanowires with cubic and hexagonal crystal symmetries, and we treat also the case of the most challenging type of heterostructure: a nanoscale crystal-phase homostructure. Finally, we discuss resonant Raman experiments that allow the determination of the energy of some electronic transitions in nanowires. We focus mostly on a very new material system, namely Ge nanowires with controlled crystal phase, but the general procedure that we establish can be applied to several types of nanostructures.
2021
Fundamental Properties of Semiconductor Nanowires
978-981-15-9049-8
978-981-15-9050-4
Semiconductor nanowires Raman spectroscopy Phonon dispersion Crystal phases Heterostructures Electronic properties
02 Pubblicazione su volume::02a Capitolo o Articolo
Addressing Crystal Structure in Semiconductor Nanowires by Polarized Raman Spectroscopy / Fasolato, Claudia; Zardo, Ilaria; De Luca, Marta. - (2021), pp. 307-348. [10.1007/978-981-15-9050-4_7].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1558098
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