2018
González, I.; Trejo, A.; Calvino, M.; Miranda, A.; Salazar, F.; Carvajal, E.; Cruz-Irisson, M.
Effects of surface and confinement on the optical vibrational modes and dielectric function of 3C porous silicon carbide: An ab-initio study Artículo de revista
En: Physica B: Condensed Matter, vol. 550, pp. 420-427, 2018, ISSN: 0921-4526.
Resumen | Enlaces | BibTeX | Etiquetas: DFPT, Dielectric function, Phonon optical modes, Porous silicon carbide
@article{GONZALEZ2018420,
title = {Effects of surface and confinement on the optical vibrational modes and dielectric function of 3C porous silicon carbide: An ab-initio study},
author = {I. Gonz\'{a}lez and A. Trejo and M. Calvino and A. Miranda and F. Salazar and E. Carvajal and M. Cruz-Irisson},
url = {https://www.sciencedirect.com/science/article/pii/S0921452618303569},
doi = {https://doi.org/10.1016/j.physb.2018.05.024},
issn = {0921-4526},
year = {2018},
date = {2018-01-01},
journal = {Physica B: Condensed Matter},
volume = {550},
pages = {420-427},
abstract = {Nanoporous silicon carbide is an interesting material with multiple potential applications, especially in supercapacitors, while there are many experimental investigations on the properties of this material, theoretical studies on its vibrational and optical properties are still scarce. This work studies the effect of quantum confinement on the dielectric function and optical vibrational modes of 3C porous silicon carbide from ab-initio calculations using density functional theory and density functional perturbation theory. The porous structures are modelled in the [001] direction by removing columns of atoms of a perfect Si crystal, obtaining two surface configurations: one with only C atoms and another one with Si atoms. Results show that the optical phonon modes of Si and C undergo a shift towards lower frequencies compared to their bulk counterparts due to phonon confinement effects. However, this shift is masked by H bending vibrations. Also, a surface H exchange process is observed on the Si-rich pore surface due to bond stretching and bending vibrations. The dielectric function analysis shows an increased optical activity in the porous cases due to a shift of the conduction band minimum towards gamma point for the C-rich case and high porosity Si-rich case, owing to quantum confinement effects. These results could be important for the applications of these nanostructures devices such as sensors and UV detectors.},
keywords = {DFPT, Dielectric function, Phonon optical modes, Porous silicon carbide},
pubstate = {published},
tppubtype = {article}
}
Nanoporous silicon carbide is an interesting material with multiple potential applications, especially in supercapacitors, while there are many experimental investigations on the properties of this material, theoretical studies on its vibrational and optical properties are still scarce. This work studies the effect of quantum confinement on the dielectric function and optical vibrational modes of 3C porous silicon carbide from ab-initio calculations using density functional theory and density functional perturbation theory. The porous structures are modelled in the [001] direction by removing columns of atoms of a perfect Si crystal, obtaining two surface configurations: one with only C atoms and another one with Si atoms. Results show that the optical phonon modes of Si and C undergo a shift towards lower frequencies compared to their bulk counterparts due to phonon confinement effects. However, this shift is masked by H bending vibrations. Also, a surface H exchange process is observed on the Si-rich pore surface due to bond stretching and bending vibrations. The dielectric function analysis shows an increased optical activity in the porous cases due to a shift of the conduction band minimum towards gamma point for the C-rich case and high porosity Si-rich case, owing to quantum confinement effects. These results could be important for the applications of these nanostructures devices such as sensors and UV detectors.
2009
Miranda, A.; Vázquez, R.; Díaz-Méndez, A.; Cruz-Irisson, M.
Optical matrix elements in tight-binding approach of hydrogenated Si nanowires Artículo de revista
En: Microelectronics Journal, vol. 40, no 3, pp. 456-458, 2009, ISSN: 1879-2391, (Workshop of Recent Advances on Low Dimensional Structures and Devices (WRA-LDSD)).
Resumen | Enlaces | BibTeX | Etiquetas: Dielectric function, Silicon nanowires, Tight-binding approach
@article{MIRANDA2009456,
title = {Optical matrix elements in tight-binding approach of hydrogenated Si nanowires},
author = {A. Miranda and R. V\'{a}zquez and A. D\'{i}az-M\'{e}ndez and M. Cruz-Irisson},
url = {https://www.sciencedirect.com/science/article/pii/S0026269208002565},
doi = {https://doi.org/10.1016/j.mejo.2008.06.018},
issn = {1879-2391},
year = {2009},
date = {2009-01-01},
urldate = {2009-01-01},
journal = {Microelectronics Journal},
volume = {40},
number = {3},
pages = {456-458},
abstract = {The dependence of the imaginary part of the dielectric function on the quantum confinement within two different schemes: intra-atomic and interatomic optical matrix elements are applied and compared. The optical spectra of Si nanowires are studied by means of a semi-empirical sp3s* tight-binding supercell model. The surface dangling bonds are passivated by hydrogen atoms. The results show that although the intra-atomic matrix elements are small in magnitude, the interference between these terms and the interatomic matrix elements contributes with nearly 25% of the total absorption. Thus, a quantitative treatment of nanostructures may not be possible without the inclusion of intra-atomic matrix elements.},
note = {Workshop of Recent Advances on Low Dimensional Structures and Devices (WRA-LDSD)},
keywords = {Dielectric function, Silicon nanowires, Tight-binding approach},
pubstate = {published},
tppubtype = {article}
}
The dependence of the imaginary part of the dielectric function on the quantum confinement within two different schemes: intra-atomic and interatomic optical matrix elements are applied and compared. The optical spectra of Si nanowires are studied by means of a semi-empirical sp3s* tight-binding supercell model. The surface dangling bonds are passivated by hydrogen atoms. The results show that although the intra-atomic matrix elements are small in magnitude, the interference between these terms and the interatomic matrix elements contributes with nearly 25% of the total absorption. Thus, a quantitative treatment of nanostructures may not be possible without the inclusion of intra-atomic matrix elements.
