References of "Molina-Sanchez, Alejandro 50002687"
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See detailDielectric screening of the Kohn anomaly of graphene on hexagonal boron nitride
Forster, F.; Molina-Sanchez, Alejandro UL; Engels, S. et al

in Physical Review. B, Condensed Matter and Materials Physics (2013), 88

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See detailContribution of the buffer layer to the Raman spectrum of epitaxial graphene on SiC(0001)
Fromm, F.; Jr, M. H. Oliveira; Molina-Sanchez, Alejandro UL et al

in New Journal of Physics (2013), 15(4), 043031

We report a Raman study of the so-called buffer layer with $(6 3 6 3)R30^ $ periodicity which forms the intrinsic interface structure between epitaxial graphene and SiC(0001). We show that this interface ... [more ▼]

We report a Raman study of the so-called buffer layer with $(6 3 6 3)R30^ $ periodicity which forms the intrinsic interface structure between epitaxial graphene and SiC(0001). We show that this interface structure leads to a non-vanishing signal in the Raman spectrum at frequencies in the range of the D- and G-band of graphene and discuss its shape and intensity. Ab initio phonon calculations reveal that these features can be attributed to the vibrational density of states of the buffer layer. [less ▲]

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See detailOptical properties of few-layers and bulk MoS2
Molina-Sanchez, Alejandro UL; Wirtz, Ludger UL

Scientific Conference (2013)

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See detailProbing Quantum Confinement within Single Core–Multishell Nanowires
Martínez-Criado, Gema; Homs, Alejandro; Alén, Benito et al

in Nano Letters (2012), 12(11), 5829-5834

Theoretically core–multishell nanowires under a cross-section of hexagonal geometry should exhibit peculiar confinement effects. Using a hard X-ray nanobeam, here we show experimental evidence for carrier ... [more ▼]

Theoretically core–multishell nanowires under a cross-section of hexagonal geometry should exhibit peculiar confinement effects. Using a hard X-ray nanobeam, here we show experimental evidence for carrier localization phenomena at the hexagon corners by combining synchrotron excited optical luminescence with simultaneous X-ray fluorescence spectroscopy. Applied to single coaxial n-GaN/InGaN multiquantum-well/p-GaN nanowires, our experiment narrows the gap between optical microscopy and high-resolution X-ray imaging and calls for further studies on the underlying mechanisms of optoelectronic nanodevices. [less ▲]

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See detailSubstrate dependence of the Raman 2D line of graphene
Wirtz, Ludger UL; Allard, Adrian; Molina-Sanchez, Alejandro UL

Scientific Conference (2012)

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See detailPhonons in single-layer and few-layer MoS2
Molina-Sanchez, Alejandro UL; Wirtz, Ludger UL

Scientific Conference (2012)

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See detailTheoretical Spectroscopy of single-layer and few-layers MoS2
Molina-Sanchez, Alejandro UL; Wirtz, Ludger UL

Scientific Conference (2012)

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See detailSemiempirical pseudopotential approach for nitride-based nanostructures and ab initio based passivation of free surfaces
Molina-Sanchez, Alejandro UL; Garcia-Cristobal, A.; Bester, G.

in Physical Review. B : Condensed Matter (2012), 86

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See detailInhomogeneous electron distribution in InN nanowires: Influence on the optical properties
Molina-Sanchez, Alejandro UL; Segura-Ruiz, J.; Garro, N. et al

in physica status solidi (c) (2012), 9(3-4), 1001--1004

In this work, we study theoretically and experimentally the influence of the surface electron accumulation on the optical properties of InN nanowires. For this purpose, the photoluminescence and ... [more ▼]

In this work, we study theoretically and experimentally the influence of the surface electron accumulation on the optical properties of InN nanowires. For this purpose, the photoluminescence and photoluminescence excitation spectra have been measured for a set of self-assembled InN NWs grown under different conditions. The photoluminescence excitation experimental lineshapes have been reproduced by a self-consistent calculation of the absorption in a cylindrical InN nanowires. With the self-consistent model we can explore how the optical absorption depends on nanowires radius and doping concentration. Our model solves the Schrödinger equation for a cylindrical nanowire of infinite length, assuming a parabolic conduction band. The columnar geometry introduces effects in both the electron density and in the self-consistent conduction band profile, with no equivalence in planar layer. On the other hand, the differences in the photoluminescence excitation spectra are related to the inhomogeneous electron distribution inside the nanowires, caused by a bulk donor concentration and a two-dimensional density of ionized surface states. For nanowire radii larger than 30 nm, such concentrations modify the absorption edge and the lineshape, respectively, and can be determined from the comparison with the experimental data (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [less ▲]

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See detailAnisotropic optical response of GaN and AlN nanowires
Molina-Sanchez, Alejandro UL; García-Cristóbal, A.

in Journal of Physics : Condensed Matter (2012), 24(29), 295301

We present a theoretical study of the electronic structure and optical properties of free-standing GaN and AlN nanowires. We have implemented the empirical tight-binding method, with an orbital basis sp 3 ... [more ▼]

We present a theoretical study of the electronic structure and optical properties of free-standing GaN and AlN nanowires. We have implemented the empirical tight-binding method, with an orbital basis sp 3 , that includes the spin–orbit interaction. The passivation of the dangling bonds at the free surfaces is also studied, together with the effects on the electronic structure of the nanowire. For both GaN and AlN nanowires, we have found a remarkable anisotropy of the optical absorption when the light-polarization changes, showing in the case of GaN a dependence on the nanowire size. [less ▲]

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See detailElectronic structure and optical properties of III-N nanowires
Molina-Sanchez, Alejandro UL

Doctoral thesis (2011)

The term III-N nanowire (NW) will refer throughout this work to the free-standing nanowires made of group-III-nitrides semiconductors, namely InN, GaN and AlN. These nanostructures have a large length ... [more ▼]

The term III-N nanowire (NW) will refer throughout this work to the free-standing nanowires made of group-III-nitrides semiconductors, namely InN, GaN and AlN. These nanostructures have a large length/diameter ratio, of the order of 100 (sev- eral micrometers versus tenths of nanometers). The term free-standing highlights the fact that the NWs are not embedded in another material. The improvement of the epitaxial techniques, and in particular, those based on III-N semiconductors, has lead an important part of the Solid State Physics community to concentrate the attention in the last years towards a better understanding of the physical properties of those NWs. Nanowires present several di erences with respect to the still widely investi- gated two-dimensional layers and the zero-dimensional nanostructures (quantum dots). We would like to highlight the following: (i) Nanowires grow strain-free (except maybe at their base), and thus with a minimal presence of dislocations or defects along the main structure. This fact opens the possibility of growing high- quality materials with an important lattice mismatch with the substrate, contrary to the situation found in quantum dots or superlattices. (ii) Depending on the NW lateral dimensions, two types of NWs can be distinguished. When the diameter is larger than 20 nm, the electronic properties of the NWs can be considered as that of a bulk material, thus making them a suitable platform to study the bulk optical and transport properties, which can be hardly investigated in bulk samples (thin lms), that grow with a high density of defects, when there is a high lattice mismatch with the substrate. (iii) For NWs of smaller diameters (. 20 nm), on the other hand, the e ects of quantum con nement can lead to important changes in the optical and transport properties, which can open the possibility of tuning the NW properties by controlling their size. One can roughly classify the investigations on nanowires into three main re- search lines. The rst one concerns the fabrication, being the molecular beam epitaxy or/and the metal organic chemical vapor deposition (MOCVD) the two techniques that allow the growth of higher quality NWs. This research area is in 2 constant development, and is not limited only to the growth of pure compound NWs, but also alloy-based NWs, which extend the possibilities of allowing beyond those possible in standard bulk growth, or axially and radially structured NWs. New physical phenomena arise which must be tacked by the physical community, in particular the e ect of the surface in the optical and transport properties of the NWs. Another focus of research is based on applications to optoelectronics devices and photovoltaic cells. In particular, III-N NWs, as InN, GaN and AlN, have attracted a special interest of the scienti c community, due to the band gap engineering. InN has a band gap of 0.67 eV (1852 nm), in the infrared, whereas GaN and AlN have a band gap of 3.5 eV (355 nm) and 6.2 eV (200 nm), respec- tively, in the ultraviolet. This opens the possibility of covering the whole solar spectrum by an appropriate alloying. In this context, the theory and numerical simulations play a crucial role in the explanation of NWs properties and a better understanding of the observed phenomena. The predictions o ered by the theory can also drive the fabrication of new heterostructures and the design of devices. In this work, we have studied theoretically by using several models, the fundamental aspects of the electronic structure and optical properties of the III-N bulk semiconductors in the rst place, and have applied afterwards such models to the investigation of the III-N nanowires physical properties. [less ▲]

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See detailPhonons in single-layer and few-layer MoS2 and WS2
Molina-Sanchez, Alejandro UL; Wirtz, Ludger UL

in Physical Review. B, Condensed Matter and Materials Physics (2011), 84

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See detailInhomogeneous free-electron distribution in InN nanowires: Photoluminescence excitation experiments
Segura-Ruiz, J.; Molina-Sanchez, Alejandro UL; Garro, N. et al

in Physical Review. B, Condensed Matter and Materials Physics (2010), 82

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See detail$LDA+U$ and tight-binding electronic structure of InN nanowires
Molina-Sanchez, Alejandro UL; Garcia-Cristobal, A.; Cantarero, A. et al

in Physical Review. B, Condensed Matter and Materials Physics (2010), 82

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See detailReversed polarized emission in highly strained $a$-plane GaN/AlN multiple quantum wells
Mata, R.; Cros, A.; Budagosky, J. A. et al

in Physical Review. B, Condensed Matter and Materials Physics (2010), 82

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