Dr. Alejandro Trejo Baños

@article{TREJO201414,

title = {Theoretical approach to the phonon modes and specific heat of germanium nanowires},

author = {A. Trejo and L. L\'{o}pez-Palacios and R. V\'{a}zquez-Medina and M. Cruz-Irisson},

url = {https://www.sciencedirect.com/science/article/pii/S0921452614003706},

doi = {https://doi.org/10.1016/j.physb.2014.05.005},

issn = {0921-4526},

year  = {2014},

date = {2014-01-01},

journal = {Physica B: Condensed Matter},

volume = {453},

pages = {14-18},

abstract = {The phonon modes and specific heat of Ge nanowires were computed using a first principles density functional theory scheme with a generalized gradient approximation and finite-displacement supercell algorithms. The nanowires were modeled in three different directions: [001], [111], and [110], using the supercell technique. All surface dangling bonds were saturated with Hydrogen atoms. The results show that the specific heat of the GeNWs at room temperature increases as the nanowire diameter decreases, regardless the orientation due to the phonon confinement and surface passivation. Also the phonon confinement effects could be observed since the highest optical phonon modes in the Ge vibration interval shifted to a lower frequency compared to their bulk counterparts.},

note = {Low-Dimensional Semiconductor Structures - A part of the XXII International Material Research Congress (IMRC 2013)},

keywords = {Germanium, Nanowires, Phonons, Specific Heat},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1063/1.4878289,

title = {Electronic states of lithium passivated germanium nanowires: An ab-initio study},

author = {A Trejo and E. Carvajal and R. V\'{a}zquez-Medina and M. Cruz-Irisson},

url = {https://aip.scitation.org/doi/abs/10.1063/1.4878289},

doi = {10.1063/1.4878289},

year  = {2014},

date = {2014-01-01},

journal = {AIP Conference Proceedings},

volume = {1598},

number = {1},

pages = {114-117},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Trejo2013,

title = {Ab-initio study of anisotropic and chemical surface modifications of $beta$-SiC nanowires},

author = {Alejandro Trejo and Jos\'{e} Luis Cuevas and Fernando Salazar and Eliel Carvajal and Miguel Cruz-Irisson},

url = {https://doi.org/10.1007/s00894-012-1605-y},

doi = {10.1007/s00894-012-1605-y},

issn = {0948-5023},

year  = {2013},

date = {2013-05-01},

journal = {Journal of Molecular Modeling},

volume = {19},

number = {5},

pages = {2043-2048},

abstract = {The electronic band structure and electronic density of states of cubic SiC nanowires (SiCNWs) in the directions [001], [111], and [112] were studied by means of Density Functional Theory (DFT) based on the generalized gradient approximation and the supercell technique. The surface dangling bonds were passivated using hydrogen (H) atoms and OH radicals in order to study the effects of this passivation on the electronic states of the SiCNWs. The calculations show a clear dependence of the electronic properties of the SiCNWs on the quantum confinement, orientation, and chemical passivation of the surface. In general, surface passivation with either H or OH radicals removes the dangling bond states from the band gap, and OH saturation appears to produce a smaller band gap than H passivation. An analysis of the atom-resolved density of states showed that there is substantial charge transfer between the Si and O atoms in the OH-terminated case, which reduces the band gap compared to the H-terminated case, in which charge transfer mainly occurs between the Si and C atoms.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{TREJO201310,

title = {Anisotropic effects on the radial breathing mode of silicon nanowires: An ab initio study},

author = {A. Trejo and R. Vazquez-Medina and G. I. Duchen and M. Cruz-Irisson},

url = {https://www.sciencedirect.com/science/article/pii/S1386947713000404},

doi = {https://doi.org/10.1016/j.physe.2013.02.006},

issn = {1386-9477},

year  = {2013},

date = {2013-01-01},

journal = {Physica E: Low-dimensional Systems and Nanostructures},

volume = {51},

pages = {10-14},

abstract = {The effect of orientation on the frequency of the radial breathing mode (RBM) of silicon nanowires (SiNWs) is investigated by means of the first principles Density Functional Theory approach through the generalized gradient approximation. We compare the RBM frequency of SiNWs orientated in three different directions, [001], [111], and [110]. The RBM is observed by the calculation of the phonon band structure and density of states of the SiNWs through the supercell finite displacement method. Results show that the SiNWs are stable in the three chosen directions since there are no negative frequencies in their phonon band structure and density of states. A clear dependence of the RBM frequency with respect to the growth direction of the nanowires and the phonon confinement was observed as the RBM frequency decreased with an inverse power law in each nanowire direction, with the fitting parameters dependent on the growth direction. These results are important since they could be used as a fingerprint to identify them within different spectroscopy techniques such as Raman.},

note = {IMRC 2012},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{molecules18044776,

title = {Computational Modeling of the Size Effects on the Optical Vibrational Modes of H-Terminated Ge Nanostructures},

author = {Alejandro Trejo and Miguel Cruz-Irisson},

url = {https://www.mdpi.com/1420-3049/18/4/4776},

doi = {10.3390/molecules18044776},

issn = {1420-3049},

year  = {2013},

date = {2013-01-01},

journal = {Molecules},

volume = {18},

number = {4},

pages = {4776--4785},

abstract = {The vibrational dispersion relations of porous germanium (pGe) and germanium nanowires (GeNWs) were calculated using the ab initio density functional perturbation theory with a generalized gradient approximation with norm-conserving pseudopotentials. Both pores and nanowires were modeled using the supercell technique. All of the surface dangling bonds were saturated with hydrogen atoms. To address the difference in the confinement between the pores and the nanowires, we calculated the vibrational density of states of the two materials. The results indicate that there is a slight shift in the highest optical mode of the Ge-Ge vibration interval in all of the nanostructures due to the phonon confinement effects. The GeNWs exhibit a reduced phonon confinement compared with the porous Ge due to the mixed Ge-dihydride vibrational modes around the maximum bulk Ge optical mode of approximately 300 cm−1; however, the general effects of such confinements could still be noticed, such as the shift to lower frequencies of the highest optical mode belonging to the Ge vibrations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Trejo2012,

title = {Computational simulation of the effects of oxygen on the electronic states of hydrogenated 3C-porous SiC},

author = {Alejandro Trejo and Marbella Calvino and Estrella Ramos and Miguel Cruz-Irisson},

url = {https://doi.org/10.1186/1556-276X-7-471},

doi = {10.1186/1556-276X-7-471},

issn = {1556-276X},

year  = {2012},

date = {2012-08-22},

journal = {Nanoscale Research Letters},

volume = {7},

number = {1},

pages = {471},

abstract = {A computational study of the dependence of the electronic band structure and density of states on the chemical surface passivation of cubic porous silicon carbide (pSiC) was performed using ab initio density functional theory and the supercell method. The effects of the porosity and the surface chemistry composition on the energetic stability of pSiC were also investigated. The porous structures were modeled by removing atoms in the [001] direction to produce two different surface chemistries: one fully composed of silicon atoms and one composed of only carbon atoms. The changes in the electronic states of the porous structures as a function of the oxygen (O) content at the surface were studied. Specifically, the oxygen content was increased by replacing pairs of hydrogen (H) atoms on the pore surface with O atoms attached to the surface via either a double bond (Xthinspace=thinspaceO) or a bridge bond (X-O-X, Xthinspace=thinspaceSi or C). The calculations show that for the fully H-passivated surfaces, the forbidden energy band is larger for the C-rich phase than for the Si-rich phase. For the partially oxygenated Si-rich surfaces, the band gap behavior depends on the O bond type. The energy gap increases as the number of O atoms increases in the supercell if the O atoms are bridge-bonded, whereas the band gap energy does not exhibit a clear trend if O is double-bonded to the surface. In all cases, the gradual oxygenation decreases the band gap of the C-rich surface due to the presence of trap-like states.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{CALVINO20121482,

title = {A Density Functional Theory study of the chemical surface modification of β-SiC nanopores},

author = {M. Calvino and A. Trejo and J. L. Cuevas and E. Carvajal and G. I. Duch\'{e}n and M. Cruz-Irisson},

url = {https://www.sciencedirect.com/science/article/pii/S0921510712000918},

doi = {https://doi.org/10.1016/j.mseb.2012.02.009},

issn = {0921-5107},

year  = {2012},

date = {2012-01-01},

journal = {Materials Science and Engineering: B},

volume = {177},

number = {16},

pages = {1482-1486},

abstract = {The dependence of the electronic band structure and density of states on the chemical surface passivation of cubic porous silicon carbide (PSiC) is investigated by means of the ab-initio Density Functional Theory and the supercell method in which pores with different sizes and morphologies were created. The porous structures were modeled by removing atoms in the [001] direction producing two different surface chemistries; one with both Silicon (Si) and Carbon (C) atoms and the other with only Si or C atoms. The changes in the electronic band gap due to a Si-rich and C-rich phase in the porous surfaces are studied with two kind of surface passivation, one with hydrogen atoms and other with a combination between hydrogen and oxygen atoms. The calculations show that for the hydrogenated case, the band gap is larger for the C-rich than for the Si-rich case. For the partial oxygenation the tendency is contrary, by decreasing and increasing the band gap for the C-rich and Si-rich configuration, respectively, according to the percentage of oxygen in the pore surface.},

note = {Advances in Semiconducting Materials},

keywords = {Density Functional Theory, Porous silicon carbide, Surface passivation},

pubstate = {published},

tppubtype = {article}

}

@article{CUEVAS20128360,

title = {Ab-initio modeling of oxygen on the surface passivation of 3CSiC nanostructures},

author = {J. L. Cuevas and A. Trejo and M. Calvino and E. Carvajal and M. Cruz-Irisson},

url = {https://www.sciencedirect.com/science/article/pii/S0169433212006289},

doi = {https://doi.org/10.1016/j.apsusc.2012.03.175},

issn = {0169-4332},

year  = {2012},

date = {2012-01-01},

journal = {Applied Surface Science},

volume = {258},

number = {21},

pages = {8360-8365},

abstract = {In this work the effect of OH on the electronic states of H-passivated 3CSiC nanostructures, was studied by means of Density Functional Theory. We compare the electronic band structure for a [111]-oriented nanowire with total H, OH passivation and a combination of both. Also the electronic states of a porous silicon carbide case (PSiC) a C-rich pore surface in which the dangling bonds on the surface are saturated with H and OH was studied. The calculations show that the surface replacement of H with OH radicals is always energetically favorable and more stable. In all cases the OH passivation produced a similar effect than the H passivation, with electronic band gap of lower energy value than the H-terminated phase. When the OH groups are attached to C atoms, the band gap feature is changed from direct to indirect. The results indicate the possibility of band gap engineering on SiC nanostructures through the surface passivation species.},

note = {VII International Workshop on Semiconductor Surface Passivation, KRAK\'{O}W, POLAND, September 11 - 15, 2011},

keywords = {Density Functional Theory, Nanowires, Porous semiconductors, Silicon carbide},

pubstate = {published},

tppubtype = {article}

}

@article{MIRANDA20121230,

title = {Interconnection effects on the electronic and optical properties of Ge nanostructures: A semi-empirical approach},

author = {A. Miranda and A. Trejo and E. Canadell and R. Rurali and M. Cruz-Irisson},

url = {https://www.sciencedirect.com/science/article/pii/S1386947712000318},

doi = {https://doi.org/10.1016/j.physe.2012.01.017},

issn = {1386-9477},

year  = {2012},

date = {2012-01-01},

journal = {Physica E: Low-dimensional Systems and Nanostructures},

volume = {44},

number = {7},

pages = {1230-1235},

abstract = {A supercell model is applied to a semi-empirical sp3s⁎ tight-binding (TB) approach to calculate the electronic band gap and imaginary part of the dielectric function of two Ge nanostructures\textemdashordered arrays of pores and stand-alone nanowires\textemdashand one example of their interconnections. The pores are modeled by removing columns of Ge atoms in the [001] direction. The results of the variation band gap are compared with those obtained by TB-sp3, TB-sp3d5s⁎, density functional theory (DFT), and experimental data. The imaginary part of the dielectric function is calculated by including both intra-atomic and inter-atomic dipole matrices using (for both) the interconnected and free standing (chessboard-like) models for the Ge skeleton. The calculation shows that although the intra-atomic matrix elements are small in magnitude a quantitative treatment of the optical absorption spectrum of Ge nanostructures may not be possible without the inclusion of these matrix elements. Finally, the calculations confirm that also ordered porous germanium (PGe) show a clear quantum confinement signature, even though the wave functions could in principle behave like delocalized Bloch states.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{TREJO2012141,

title = {Phonon band structure of porous Ge from ab initio supercell calculation},

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

url = {https://www.sciencedirect.com/science/article/pii/S016793171100503X},

doi = {https://doi.org/10.1016/j.mee.2011.05.007},

issn = {0167-9317},

year  = {2012},

date = {2012-01-01},

journal = {Microelectronic Engineering},

volume = {90},

pages = {141-144},

abstract = {The phonon band structures for porous Ge (PGe) are performed by means of full ab initio calculations. The supercell technique is used and ordered pores are produced by removing columns of Ge atoms from their crystalline structures. The nanostructures are fully relaxed in order to obtain the minimum energy and avoid negative frequencies derived from instabilities of the system. The phonon dispersion and phonon density of states were studied using the Density Functional Theory through the finite displacement algorithm. The results show for the dehydrogenated PGe case a notable shift of the highest optical mode towards lower frequencies with respect to the bulk crystalline Ge. This fact is in agreement with the experimental data such as Raman scattering.},

note = {Micro\&Nano 2010},

keywords = {Density Functional Theory, Phonons, porous germanium, Supercell approach},

pubstate = {published},

tppubtype = {article}

}

@article{TREJO201292,

title = {Phonon optical modes and electronic properties in diamond nanowires},

author = {A. Trejo and A. Miranda and L. Ni\~{n}o Rivera and A. D\'{i}az-M\'{e}ndez and M. Cruz-Irisson},

url = {https://www.sciencedirect.com/science/article/pii/S016793171100476X},

doi = {https://doi.org/10.1016/j.mee.2011.04.052},

issn = {0167-9317},

year  = {2012},

date = {2012-01-01},

journal = {Microelectronic Engineering},

volume = {90},

pages = {92-95},

abstract = {A local bond-polarization model based on the displacement\textendashdisplacement Green’s function and the Born potential are applied to study the confined optical phonons and Raman scattering of diamond nanowires (DNWs). Also, the electronic band structure of DNWs are investigated by means of a semi-empirical tight-binding approach and compared with density functional theory within local density approximation. The supercell technique is applied to model DNWs along [001] direction preserving the crystalline diamond atomic structure. The results of both phonons and electrons show a clear quantum confinement signature. Moreover, the highest energy Raman peak shows a shift towards low frequencies respect to the bulk crystalline diamond, in agreement with experimental data.},

note = {Micro\&Nano 2010},

keywords = {Diamond, Nanowires, Phonons, Raman scattering, Tight-binding},

pubstate = {published},

tppubtype = {article}

}

@article{57030389006,

title = {Theoretical study of the electronic band gap in B-SiC nanowires},

author = {M. Ramos A. Calvino Trejo},

url = {https://www.redalyc.org/articulo.oa?id=57030389006},

issn = {0035-001X},

year  = {2011},

date = {2011-01-01},

urldate = {2011-01-01},

journal = {Revista Mexicana de F\'{i}sica},

keywords = {Keywords; Density functional theory; nanowires; silicon carbide.; Descriptores; Teor\'{i}a del funcional de la densidad; nanoalambres; carburo de silicio.},

pubstate = {published},

tppubtype = {article}

}

@article{https://doi.org/10.1002/qua.22647,

title = {Chemical surface passivation of 3C-SiC nanocrystals: A first-principle study},

author = {A. Trejo and M. Calvino and M. Cruz-Irisson},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/qua.22647},

doi = {https://doi.org/10.1002/qua.22647},

year  = {2010},

date = {2010-01-01},

journal = {International Journal of Quantum Chemistry},

volume = {110},

number = {13},

pages = {2455-2461},

abstract = {Abstract The effect of the chemical surface passivation, with hydrogen atoms, on the energy band gap of porous cubic silicon carbide (PSiC) was investigated. The pores are modeled by means of the supercell technique, in which columns of Si and/or C atoms are removed along the [001] direction. Within this supercell model, morphology effects can be analyzed in detail. The electronic band structure is performed using the density functional theory based on the generalized gradient approximation. Two types of pores are studied: C-rich and Si-rich pores surface. The enlargement of energy band gap is greater in the C-rich than Si-rich pores surface. This supercell model emphasizes the interconnection between 3C-SiC nanocrystals, delocalizing the electronic states. However, the results show a clear quantum confinement signature, which is contrasted with that of nanowire systems. The calculation shows a significant response to changes in surface passivation with hydrogen. The chemical tuning of the band gap opens the possibility plenty applications in nanotechnology. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2455\textendash2461, 2010},

keywords = {Density Functional Theory, Porous silicon carbide, silicon carbide nanowires},

pubstate = {published},

tppubtype = {article}

}