Dr Álvaro Miranda Durán

@article{TREJO2016215,

title = {Optical vibrational modes of Ge nanowires: A computational approach},

author = {A. Trejo and A. Miranda and L. K. Toscano-Medina and R. V\'{a}zquez-Medina and M. Cruz-Irisson},

url = {https://www.sciencedirect.com/science/article/pii/S0167931716302258},

doi = {https://doi.org/10.1016/j.mee.2016.04.024},

issn = {0167-9317},

year  = {2016},

date = {2016-01-01},

journal = {Microelectronic Engineering},

volume = {159},

pages = {215-220},

abstract = {Although Ge nanowires (GeNWs) have been extensively studied in the last decade the information about their vibrational modes is still scarce, their correct comprehension could hasten the development of new microelectronic technologies, therefore, in this work we aimed to study the vibrational properties, Raman and IR and spectrum of GeNWs using the first principles density functional perturbation theory. The nanowires are modelled in the [001] direction and all dangling bonds are passivated with H and Cl atoms. Results show that the vibrational modes can be classified in three frequency intervals, a low frequency one (between 0 and 300cm−1) of mainly GeGe vibrations, and two of GeH bending and stretching vibrations (400\textendash500cm−1 and 2000cm−1, respectively). There is a shift of the highest optical modes of GeGe vibrations compared to their bulk counterparts due to phonon confinement effects, however it is masked by some GeH bond bending modes as demonstrated by the IR and Raman responses. The Cl passivated case shows a larger number of modes at lower frequencies due to the higher mass of Cl compared to H, which in turn reduces the red shift of the highest optical modes frequencies. These results could be important for the characterization of GeNWs with different surface passivations.},

note = {Micro/Nano Devices and Systems 2015},

keywords = {Density functional perturbation theory, Germanium nanowires, Phonons, Raman spectrum},

pubstate = {published},

tppubtype = {article}

}

@article{MIRANDA2009439,

title = {Modelling of electronic and phononic states of Ge nanostructures},

author = {A. Miranda and M. Cruz-Irisson and C. Wang},

url = {https://www.sciencedirect.com/science/article/pii/S0026269208002516},

doi = {https://doi.org/10.1016/j.mejo.2008.06.009},

issn = {1879-2391},

year  = {2009},

date = {2009-01-01},

urldate = {2009-01-01},

journal = {Microelectronics Journal},

volume = {40},

number = {3},

pages = {439-441},

abstract = {The electronic band structure of ordered porous germanium (PGe) and germanium nanowires (GeNW) are studied by means of an sp3s* tight-binding approach. Within the linear response theory, a local bond-polarization model based on the displacement\textendashdisplacement Green\'s function and the Born potential including central and non-central interatomic forces are used to investigate the Raman response and the phonon band structure of PGe and GeNW. This study is carried out by means of a supercell model, in which along the [001] direction empty-column pores and nanowires are constructed preserving the crystalline Ge atomic structure. An advantage of this model is the interconnection between Ge nanocrystals in PGe and then, all the electronic and phononic states are delocalized. However, the results of both elementary excitations show a clear quantum confinement signature. Moreover, the highest-energy Raman peak in both PGe and GeNW shows a shift towards lower frequencies with respect to that of bulk crystalline Ge, in good agreement with the experimental data.},

note = {Workshop of Recent Advances on Low Dimensional Structures and Devices (WRA-LDSD)},

keywords = {Germanium nanowires, porous germanium, Raman response, Tight-binding model},

pubstate = {published},

tppubtype = {article}

}